experiment yang

Quantum 'yin-yang' shows two photons being entangled in real-time

The stunning experiment, which reconstructs the properties of entangled photons from a 2D interference pattern, could be used to design faster quantum computers.

Scientists have used a first-of-its-kind technique to visualize two entangled light particles in real time — making them appear as a stunning quantum "yin-yang" symbol.

The new method, called biphoton digital holography, uses an ultra high-precision camera and could be used to massively speed up future quantum measurements.

The researchers published their findings Aug. 14 in the journal Nature Photonics .

Related: Bizarre particle that can remember its own past created inside quantum computer

Quantum entanglement — the weird connection between two far-apart particles that Albert Einstein objected to as "spooky action at a distance" — enables two light particles, or photons, to become inextricably bound to each other, so that a change to one causes a change in the other, no matter how far apart they are. 

To make accurate predictions about a quantum object, physicists need to find its wavefunction: a description of its state existing in a superposition of all the possible physical values a photon can take. Entanglement makes finding the wavefunction of two connected particles a challenge, as any measurement of one also causes an instantaneous change in the other. 

Physicists usually approach this hurdle through a method known as quantum tomography. By taking a complex quantum state and applying a projection to it, they measure some property belonging to that state, such as its polarization or momentum, in isolation from others. 

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By repeating these measurements on multiple copies of the quantum state, physicists can build up a sense of the original from lower-dimensional slices — like reconstructing the shape of a 3D object from the 2D shadows it casts on surrounding walls. 

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This process gives all the right information, but it also requires a lot of measurements and spits out plentiful "disallowed" states that don't follow the laws of physics to boot. This leaves scientists with the onerous task of painstakingly weeding out nonsensical, unphysical states, an effort that can take hours or even days depending on a system's complexity.

To get around this, the researchers used holography to encode information from higher dimensions into manageable, lower-dimensional chunks.

Optical holograms use two light beams to create a 3D image: one beam hits the object and bounces off of it, while the other shines on a recording medium. The hologram forms from the pattern of light interference, or the pattern in which the peaks and troughs of the two light waves add up or cancel each other out. The physicists used a similar method to capture an image of the entangled photon state through the interference pattern they made with another known state. Then, by capturing the resulting image with a nanosecond precise camera, the researchers teased apart the interference pattern they received — revealing a stunning yin-yang image of the two entangled photons.

"This method is exponentially faster than previous techniques, requiring only minutes or seconds instead of days," study co-author Alessio D'Errico , a postdoctoral fellow at the University of Ottawa in Canada, said in a statement . 

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.

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Physicists Visualize Quantum Yin-Yang in Entangled Light Experiment

Never let it be said that scientists don't have an eye for the sublime.

Encoding and deciphering a Chinese symbol for duality and harmony into the quantum states of two entangled photons, physicists recently demonstrated the superior efficiency of a new analytical technique.

Researchers from the Sapienza University of Rome and the University of Ottawa in Canada used a method similar to a popular holographic technique to quickly and reliably measure information of a particle's position.

By improving on existing methods for capturing critical details on various states in entangled particles, the team hopes to provide engineers with new computing and imaging tools that form the basis of quantum technologies.

Individual photons, like any particle, are best described as a slowly evolving range of possibilities before a measurement bestows hard, factual numbers on them. Polarization, spin, momentum, even their position, are as unsettled as a coin tumbling through the air until a metaphorical hand slaps it into a single state.

If two photons share a history of some kind – like two coins plucked from the same purse – slapping one is as good as stopping the other mid-flight. Entangled as they are, knowing something about one will give you a measure of the other as if it too were slapped into place.

The fundamentals of this game-of-chance form the very basis of quantum computers . Numerous entangled particles called qubits can have one of their states read in ways that will rapidly answer specially formulated mathematical questions.

Yet why use just one state when particles have so many undecided characteristics to choose from, turning simple 2D qubits into 'multi-dimensional' qudits ?

To build a more complex picture of a particle, physicists can take a series of measures, just as multiple X-rays are used to build a 3D picture of a body in computerized tomography .

One major problem with adapting quantum tomography to capture numerous dimensions of a particle is the work required. As the number of states being read grows, measurements skyrocket, costing time and dramatically increasing the risk of errors.

Biphoton digital holography could change that. Just as conventional holograms allow us to retrieve 3D information from a 2D surface, it's possible to use the way waves interfere with one another to quickly and precisely infer additional dimensions from just a few details carried between a pair of photons.

Physicists already use the interference of entangled particles to map hidden objects in what's known as ghost imaging . Knowing just enough about the positioning of one photon sent down a single pathway, it's possible to learn the secrets of its partner's journey down a second passage by overlapping their waves.

Applying tricks of holography, the researchers were able to read positional information in the interference of two separated light waves, recovering enough information to recreate a yin-and-yang symbol programmed into the photon-generating apparatus.

As simple as the yin-and-yang looks, this single static image represents a significant leap in measuring numerous quantum states in a short time.

"This method is exponentially faster than previous techniques, requiring only minutes or seconds instead of days," says University of Ottawa physicist Alessio D'Errico.

"Importantly, the detection time is not influenced by the system's complexity – a solution to the long-standing scalability challenge in projective tomography."

This research was published in Nature Photonics .

Quantum mechanics: the yin and yang of photon entanglement

• Researchers in Canada and Italy have come up with a new way of visualising particles in real time
• The approach could help overcome problems with scalability and time, a professor says

A new real-time way of visualising entangled photons – the basic particles of light – has revealed a yin-yang-like image.

The technique, known as biphoton digital holography, visualised the “wave function” of the photons and was detailed in a paper published in the journal Nature Photonics last week by a team of researchers from the University of Ottawa and Sapienza University in Rome.

The work comes four years after the capture of the first photo of quantum entanglement by physicists at the University of Glasgow in Scotland.

In that image the entanglement looked like a broken doughnut.

The yin-yang symbol represents opposite but connected forces and is known in China as “taijitu”, a concept that dates back to the Song dynasty (960–1279).

“It’s not the first image of quantum entanglement but this is eye-attracting research,” said Yin Zhangqi, a professor at the Beijing Institute of Technology’s school of physics.

He said the taijitu pattern in this paper could not be “taken for granted”, saying the resulting image could have something to do with the light beam used by the researchers.

Yin said that taijitu had appeared in the quantum world before. In a paper published in a top physical academic journal in May, a group of Chinese scientists generated a figure that was quite similar to the yin-yang shape, using a different method, he said.

Quantum entanglement underpins the strange science of quantum mechanics and has huge practical implications for areas such as computing.

Researchers have harnessed its power for quantum cryptography, technology that uses the laws of physics to prevent eavesdropping. It also has the potential to advance other quantum technologies such as quantum imaging.

Quantum entanglement occurs when two particles become inextricably linked, and whatever happens to one immediately affects the other, regardless of how far apart they are.

It has been likened to a pair of shoes – the moment one shoe is identified, the nature of the other, whether it is the left or right shoe, is immediately known.

Just like the shoe’s “wave function” carries information like size, colour, left or right; similarly, in quantum physics, the wave function enables scientists to predict the probable outcomes of various properties of a quantum entity, such as position and velocity.

But pinning down the function of a quantum system, a process called quantum tomography, is challenging and only increases in difficulty as the system becomes more complex.

Previous experiments conducted with the standard approach measuring the “high-dimensional” quantum state of two entangled photons could take hours or even days.

In this latest study, the researchers developed a quantum tomography technique called biphoton digital holography. They superimposed the entangled photons with a known quantum state, and then analysed the spatial distribution of the positions where two photons arrive simultaneously to capture a “coincidence image”.

“This study made a great contribution to quantum state tomography,” said Wang Jindong, a professor at South China Normal University in Guangdong province.

Wang said that knowing the characteristics of the wave function was essential to apply quantum physics.

The mainstream method, however, was time-consuming and not very scalable, but this team was delivering a new approach that might go some way to overcoming these limitations, he said.

What Is The Double-Slit Experiment?

The double-slit experiment, observation affects reality, the various interpretations:.

The double-slit experiment shows the duality of the quantum world. A photon’s wave/particle duality is affected when it is observed.

Light has been one of the major areas of inquiry for physicists since we first began questioning the world around us. Understandably so, as it is the medium by which we see, measure and understand the world. It holds a powerful symbolism in our imaginations, is reflected in our religions and is famously quoted in our scriptures.

Rigorous science has enlightened our ignorance about Light. Until the 1800s, light was thought to be made up of particles, attested by Newtonian physics.

This came rather intuitively, as we see light traveling in a straight line, like bullets coming out of a gun.

However, nature is often weirder than our expectations and light’s weird behavior was first shown by Thomas Young in his now heavily worked upon and immortalized double-slit experiment. This experiment provides some fascinating insights into the minute workings of nature and has challenged everything we know about light, matter, and reality itself. Let’s revisit the experiment that has baffled legendary scientists – including Einstein!

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The experiment is pretty straightforward, with very few parts. There are three main components:

• A source of light or matter – photons, electrons, bullets

• Two narrow slits for the source to pass-through.

• A projection screen, where the source makes its impression. The pattern of the impression tells us if it is a wave or a particle.

The objective of the experiment is to see the underlying make-up of light and matter.

Let’s start with something familiar, bullets from a machine gun. Our gun fires bullets at regular intervals towards the range of the two slits.

Two straight lines appear on the projector. The graph pattern is that of two mountains; where the crests imply the impression points, and the troughs imply empty places.

The thing to note here is, if we close S2 and fire the gun, only one line appears. Thus, we can safely say that S is equal to the sum of S1 and S2, i.e., S = S1 + S2.

Light is the next source for the experiment. The impression appears as bundles of photons fire through the two slits. What is the pattern you think will emerge? Is it similar to that of bullets? Well, light consists of bullet-like particles, so it isn’t farfetched to say the pattern will be the same.

To everyone’s surprise, however, the impression isn’t of two straight lines. The graph pattern that emerges is an interference pattern; there is the brightest impression in the center, and recedes on both sides. An interference pattern is only made when two waves interfere with each other; there is no other possible explanation to it. The pattern shows that the light is moving in waves.

The waves from the two slits are colliding with each other. There is a peculiar formation that develops when two waves collide. A wave has a crest (the part above) and a trough (the part below).

When the crest of one wave collides with the crest of another, it adds and forms constructive interference, seen as a bright spot on the projector. When the crest of one wave and trough of another collide, they cancel each other out and form a destructive pattern, which results in dark spots between the impressions on the projector.

The second slit is closed and the experiment is done again. Now with one slit to move through, the photons form a straight line. Note, here S is not equal to the sum of S1 and S2, and this is also where light’s wave-particle duality comes into focus.

This revelation changed our thinking about light, but the rabbit hole doesn’t end there; things just get weirder when we further iterate the experiment. Now, instead of flashing a bunch of photons together, only single photons are fired through the slits at regular intervals. Given that it is a single photon, and has no other wave to interact with, we can say that the photon will make a single line on the projector, yet the result is counter-intuitive; the formation on the projector is still an interference pattern!

How can this be? How can a single photon know about the photons coming after it and form a pattern resembling that of the group being shot together?

This is where quantum spookiness begins and things get pretty far out. It appears that a single photon is traveling through both the slits and colliding with itself to form the interference pattern. This has bothered physicists a lot, as it does not obey the laws that we see in our Newtonian scale. It turns out that a large assemblage appears to behave in a way that is different from the behavior of its minuscule components.

Now, let’s hit a home run and take this weirdness to another level. This last iteration of the experiment will make you appreciate nature’s absurdness and how totally wacky our world truly is.

Also Read: Wave-Particle Duality: Is An Electron A Particle Or A Wave?

At this point, we have established that a single photon travels from both the slit at the same time and collides with itself to form the interference pattern. As classical physics dictates, it is impossible for the same photon to move through the two slits at the same time. Perhaps it is splitting itself into two parts and interacting with itself. The only way to know is to watch. A detector is placed in one of the slits so when the photon passes through the slit, the detector identifies it.

As the photon passes through the slit, the detector identifies it. The pattern that emerges on the projector is a single line.

Just when you think you’re coming to terms with the quantum scale, things slip over your head. The act of measuring or observing the photon makes it go through only one path, making the impression on the projector of a particle. It doesn’t interact with itself anymore and no interference pattern emerges. When the experiment is carried out with varying degrees of detection, so that the detection is dimmer on every passing photon (say 7-10 photons are being detected and that number keeps decreasing), then the interference pattern starts to slowly emerge again. The photons act as a wave when not being observed and act as particles when they are being observed.

Also Read: What Is The Observer Effect In Quantum Mechanics?

The double-slit experiments is one of the most iterated experiments in scientific history. Electrons, atoms, molecules and even complex fullerenes like Buckyballs have been used as sources for the experiment. The same results are obtained using every source; the pattern is consistent in both light and matter.

Things on the quantum scale don’t follow the deterministic laws of the macro scale. There are many interpretations of this quantum phenomenon. The Copenhagen Interpretation states that the interference pattern is all the probable functions of the photon (a wave function) and the act of observing or measuring it makes the wave select one of the many alternatives (collapsing of the wave function).

Another interpretation is the many-worlds theory, which states that all the possible states of the photon’s wave function exist simultaneously and our detection is just this particular instance of the wave function.

The theories tend to run wild and it’s safe to say that the quantum realm is a little slippery to wrap your head around. However, there’s no need to feel bad, as you’re in good company. As Richard Feynman said:

Also Read: Why Is Quantum Mechanics So Difficult To Understand?

• Copenhagen Interpretation. The University of Oregon
• A Review and Response to the Book "The Grand Design" by ... - TASC. tasc-creationscience.org
• Chapter 14 Interference and Diffraction. web.mit.edu
• Young’s Double Slit Experiment - pressbooks.online.ucf.edu
• Lecture Notes | Quantum Physics III - MIT OpenCourseWare. MIT OpenCourseWare

Vishal is an Architect and a design aficionado. He likes making trippy patterns in his computer. Fascinated by technology’s role in humanity’s evolution, he is constantly thinking about how the future of our species would turn out – sometimes at the peril of what’s currently going on around him.

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Yin-Yang? Researchers Capture The Mysterious Dance of Entangled Photons in Real-Time

Matt swayne.

• August 23, 2023

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Insider Brief

• University of Ottawa researchers demonstrated a novel technique that allows the visualization of the wave function of two entangled photons.
• The team was led by Ebrahim Karimi, Canada Research Chair in Structured Quantum Waves.
• The researchers said the work has the potential to accelerate quantum technology advancements, such as improving quantum state characterization, quantum communication, and developing new quantum imaging techniques.
• Image: (left to right): Dr. Alessio D’Errico, Dr. Ebrahim Karimi, and Nazanin Dehghan (UOttawa)

PRESS RELEASE — Researchers at the University of Ottawa, in collaboration with Danilo Zia and Fabio Sciarrino from the Sapienza University of Rome , recently demonstrated a novel technique that allows the visualization of the wave function of two entangled photons, the elementary particles that constitute light, in real-time.

Using the analogy of a pair of shoes, the concept of entanglement can be likened to selecting a shoe at random. The moment you identify one shoe, the nature of the other (whether it is the left or right shoe) is instantly discerned, regardless of its location in the universe. However, the intriguing factor is the inherent uncertainty associated with the identification process until the exact moment of observation.

Knowing the wave function of such a quantum system is a challenging task – this is also known as  quantum state tomography  or  quantum tomography  in short. With the standard approaches (based on the so-called  projective operations ), a full tomography requires large number of measurements that rapidly increases with the system’s complexity (dimensionality). Previous experiments conducted with this approach by the research group showed that characterizing or measuring the high-dimensional quantum state of two entangled photons can take hours or even days. Moreover, the result’s quality is highly sensitive to noise and depends on the complexity of the experimental setup.

The projective measurement approach to quantum tomography can be thought of as looking at the shadows of a  high-dimensional  object projected on different walls from independent directions. All a researcher can see is the shadows, and from them, they can infer the shape (state) of the full object. For instance, in CT scan (computed tomography scan), the information of a 3D object can thus be reconstructed from a set of 2D images.

In classical optics, however, there is another way to reconstruct a 3D object. This is called digital holography, and is based on recording a single image, called interferogram, obtained by interfering the light scattered by the object with a reference light.

The team, led by Ebrahim Karimi, Canada Research Chair in Structured Quantum Waves, co-director of  uOttawa Nexus for Quantum Technologies (NexQT) research institute  and associate professor in the Faculty of Science, extended this concept to the case of two photons. Reconstructing a biphoton state requires superimposing it with a presumably well-known quantum state, and then analyzing the spatial distribution of the positions where two photons arrive simultaneously. Imaging the simultaneous arrival of two photons is known as a coincidence image. These photons may come from the reference source or the unknown source. Quantum mechanics states that the source of the photons cannot be identified. This results in an interference pattern that can be used to reconstruct the unknown wave function. This experiment was made possible by an advanced camera that records events with nanosecond (one 1 000 000 000 th  of a second) resolution on each pixel.

Dr. Alessio D’Errico, a postdoctoral fellow at the University of Ottawa and one of the co-authors of the paper, highlighted the immense advantages of this innovative approach: “This method is exponentially faster than previous techniques, requiring only minutes or seconds instead of days. Importantly, the detection time is not influenced by the system’s complexity – a solution to the long-standing scalability challenge in projective tomography.”

The impact of this research goes beyond just the academic community. It has the potential to accelerate quantum technology advancements, such as improving quantum state characterization, quantum communication, and developing new quantum imaging techniques.

The study ‘ Interferometric imaging of amplitude and phase of spatial biphoton states’ north_east external link was published in  Nature Photonics  on August 14, 2023.

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Quantum Yin-Yang? Scientists visualize quantum entanglement of photons for the first time

In a quantum twist, researchers glimpse the synchronized waltz of entangled photons.

You may have heard of light as both particles and waves, but have you ever imagined the secret dance within? Researchers from the University of Ottawa and Sapienza University in Rome have just uncovered a groundbreaking technique that enables the real-time visualization of the wave function of entangled photons — the fundamental components of light.

The snapshot of a quantum dance

Imagine choosing a random shoe from a pair. If it’s a “left” shoe, you immediately know the other shoe you’ve yet to unbox is meant to go on your right foot. This instantaneous information is certain whether the shoe box is within hand’s reach or 4.3 light-years away on some planet in the Alpha Centauri system.

This analogy, though not perfect, captures the essence of quantum entanglement. At its core, quantum entanglement refers to the phenomenon where two or more particles become deeply interconnected in such a way that their properties become correlated, regardless of the spatial separation between them. This means that the state of one particle instantly influences the state of another, even if they are light-years apart.

Quantum entanglement might sound like something out of science fiction, but it’s a very real phenomenon that has been observed in experiments. It challenges our conventional understanding of how the world works and delves into the strange and wondrous realm of quantum physics, where particles can be in multiple states at once and influence each other in ways that defy our everyday intuition.

This instantaneous connection seems to defy the fundamental speed limit of information transfer imposed by Einstein’s theory of relativity. Indeed, the concept of entanglement was famously challenged by Albert Einstein, Boris Podolsky, and Nathan Rosen in a 1935 paper known as the EPR paradox. They proposed that entanglement was an incomplete description of physical reality, asserting that quantum mechanics must be missing hidden variables that determine particle properties independently.

However, subsequent experiments, notably the Bell tests , demonstrated that the EPR paradox couldn’t be resolved with classical hidden variables. The results of these experiments aligned with quantum predictions, highlighting the genuine non-local nature of entanglement.

Wave functions, crucial in quantum mechanics, can provide important insight into a particle’s quantum state. If we stick to the shoe analogy, the shoe’s “wave function” carries information like size, color, left or right, and so on. But in quantum physics, scientists usually describe a particle’s wave function in terms of position, velocity, spin, and other quantum properties.

Holography: A New Dimension of Quantum Insight

As you might imagine, determining the wave function of a quantum system is no trivial task. This process, known as quantum tomography, typically involves cumbersome measurements that introduce “dimensionality”, the number of distinct properties or characteristics that a quantum system can possess and be measured for.

In quantum mechanics, each dimension represents a distinct property that can be measured, such as position, momentum, spin, etc. When dealing with entangled particles or more complex quantum systems, the number of dimensions grows significantly. This can result in entangled systems existing in a high-dimensional space, where the dimensions correspond to various properties of the entangled particles.

Previous experiments involving quantum tomography measuring the high-dimensional quantum state of two entangled photons could take hours or even days. Not only does the process take a very long time, the quality of the results is questionable, especially for increasingly complex systems. Imagine trying to reconstruct a high-dimensional object from its shadows cast on different walls. That’s the challenge quantum scientists face when tackling quantum tomography.

But what if instead of just shadows, we have holograms? In classical optics, digital holography creates a three-dimensional image using a single interferogram — a result of light interference. The team of researchers led by Ebrahim Karimi from Ottawa University extended this concept to the realm of entangled photons.

To uncover the quantum secrets, researchers superimposed the entangled photons with a known quantum state. They watched as the photons arrived simultaneously, creating a breathtaking so-called “coincidence image”. It’s like capturing two dancers in perfect synchronization, frozen in time.

This key discovery was made possible thanks to a cutting-edge camera with nanosecond precision. This camera captured the photons’ synchronized arrival, revealing an intricate interference pattern. This pattern, akin to a mesmerizing choreography, held the key to reconstructing the elusive wave function.

“This method is exponentially faster than previous techniques, requiring only minutes or seconds instead of days. Importantly, the detection time is not influenced by the system’s complexity—a solution to the long-standing scalability challenge in projective tomography,” said Dr. Alessio D’Errico, a postdoctoral fellow at the University of Ottawa and one of the co-authors of the paper.

Quantum entanglement might sound like an abstract concept, but it has profound practical implications. Researchers have harnessed entanglement for quantum cryptography, a method of secure communication based on the principles of quantum mechanics. This technology enables the transmission of cryptographic keys that are inherently secure, as any eavesdropping attempts would disrupt the entanglement and be detectable.

Entanglement also plays a pivotal role in quantum computing, a field that holds the promise of solving complex problems beyond the capabilities of classical computers. Quantum bits (qubits), which can be in entangled states, allow for exponentially faster computation due to their ability to exist in multiple states simultaneously.

As such, the findings add a new layer of understanding into quantum wave functions that could make quantum computers and other applications more stable. This method may also lead to the development of new quantum imaging techniques.

The findings appeared in the journal Nature Photonics .

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• 15 January 2024

How a forgotten physicist’s discovery broke the symmetry of the Universe

• Suzie Sheehy 0

Suzie Sheehy is an associate professor in physics at the University of Melbourne, Australia.

You can also search for this author in PubMed   Google Scholar

You have full access to this article via your institution.

Parity symmetry says that something viewed in a mirror should look the same. Credit: Getty

When a ‘scanner’ called Minnie van der Merwe handed Rosemary Brown a photographic slide with an unusual configuration of particle tracks, the physicist knew that she was on to something. “I looked very carefully and thought: this is it,” she says.

That was in 1948, when Brown — now 97 and known by her married name of Fowler — was a 22-year-old PhD student in Cecil Powell’s group at the University of Bristol, UK. She was looking at particle tracks in photographic emulsions that had been exposed to cosmic rays. Before the advent of particle accelerators, such emulsions were the main source of data for exotic high-energy particles. Fowler was in little doubt about what she had found in what became labelled the ‘ k -track’ plate — but working out the ‘why’ of her discovery occupied particle physicists for the best part of a decade. When they finally managed it, it blew apart the idea that the laws of nature adhered to certain symmetrical ways of working, with reverberations that continue to this day.

Does quantum theory imply the entire Universe is preordained?

The decades either side of the Second World War were a boom time for particle discovery. The 1930s had seen the list of subatomic particles grow beyond the duo of the electron and proton, with the discovery of the neutron, the muon (a heavier version of the electron) and the first antimatter particle, the positron. In 1947, Powell confirmed the existence of the pion 1 , the first of a new class of particles known as mesons. These were predicted in 1934 by Japanese physicist Hideki Yukawa to be carriers of the strong nuclear force — one of the four fundamental forces of nature. (Mesons are now known to be made up of quarks, the interactions of which, through the exchange of gluons, are the basis of this force.)

In December 1947, George Rochester and Clifford Butler at the University of Manchester, UK, took the meson discovery a stage further. They detailed how, in 5,000 cloud-chamber photographs, they had found evidence 2 of what they called the theta zero ( ϴ 0 ), a neutrally charged meson that decayed into pions. Fowler’s discovery just a few months later was both similar and strikingly different. Powell’s laboratory had perfected the technique of using emulsion plates to investigate the contents of cosmic rays entering Earth’s atmosphere. The k- track plate came from a set exposed at the high-altitude lab, at Jungfraujoch, Switzerland, located 3,571 metres above sea level. It revealed a particle, identified as ‘tau’, with the same mass as a ϴ 0 , but that decayed differently: to three pions, rather than two.

A mirror crack’d

An intense period of work followed the discovery. “A lot of measurement and calculation had to be done before the finding could be published. We knew it was an important discovery so worked very hard to get everything done quickly,” says Fowler. The team wrote three papers in quick succession, including two that were published in Nature in January 1949. All three listed Fowler (then Brown) as the first author 3 – 5 . This followed the convention that authors be listed in alphabetical order, but also recognized that she had been the one to make the discovery.

Grasping the implications of Fowler’s discovery means delving into what was thought to be a fundamental symmetry of nature, known as parity. The statement ‘parity symmetry is conserved’ amounts to saying that a mirror-reflected version of a physical process should occur just as readily in nature as the original process does. In particle physics, parity symmetry is expressed by a quantum number describing how a particle acts if you flip it in one spatial coordinate. Total parity is calculated by multiplying the parity numbers of all the particles involved at the different stages of a particle process. If parity symmetry is conserved, the total parity cannot change.

The particle-physics breakthrough that paved the way for the Higgs boson

A pion has a parity of −1, so the three-pion end state of Fowler’s tau-meson decay also has an overall parity of −1. But the two-pion end state of the ϴ 0 decay has parity +1. If parity is conserved, the two initial particles must have distinct parities, too — and should therefore be different types of particle. But no theoretical concept could explain why two particles of different types could have exactly the same mass. This became known as the tau–theta puzzle.

After Fowler’s first observation, many groups followed in her tracks. They scoured cloud-chamber photographs and flew stacks of emulsions high into the atmosphere in weather balloons to look for signs of the tau-meson decay. By 1953, this activity had led to a total of 11 events. By 1955, 35 more events had been produced using the Bevatron, an enormous particle accelerator at Lawrence Berkeley National Laboratory in Berkeley, California, that provided an alternative source, beyond cosmic rays, of high-energy particles. Along the way, a new naming convention was introduced: the initial particles became known as K mesons or kaons, and theta and tau referred instead to the decay modes that resulted in two and three pions, respectively. Given that all the researchers involved would have been familiar with Fowler’s k -track, it seems a highly likely source for this convention.

With more-precise measurements, the masses of the two types of kaon remained identical and the tau–theta puzzle only became more perplexing. Finally, in April 1956, particle physicists gathered at a conference in Rochester, New York, to thrash out exactly what was going on with kaons, and several other confusing ‘strange’ particles that had been discovered in the meantime. Neither Fowler nor Powell was there, but luminaries such as Murray Gell-Mann and Richard Feynman were. In Gell-Mann’s recollection, Feynman was sharing a room with experimentalist Martin Block, who asked him: “What if parity isn’t conserved? Then couldn’t the tau and theta be the same thing?” Feynman proposed this at the meeting. It turned out that no one had ever actually proved that parity was conserved, especially in the weak-nuclear interaction, which governs kaon decays.

In 1948, Rosemary Brown (back left, next to pillar) was one of few female physicists at Bristol. Credit: Archives of the School of Physics/University of Bristol

Theorists Tsung-Dao Lee and Chen-Ning Yang were also at that meeting, and that October proposed that parity might be violated 6 . At first their paper was viewed with scepticism, with Feynman even placing a personal bet with odds of 50:1 against parity violation. An experiment was needed to confirm or refute the idea. That experiment was conducted, also in 1956, by Chien-Shiung Wu at the National Bureau of Standards in Washington DC. She showed conclusively that parity was not conserved in the β decay of cobalt-60, which also occurs through the weak nuclear force 7 . Other experimental results soon added to the pile, until it was undeniable. The solution to the tau–theta puzzle was that the two types of kaon were one and the same, but parity was not a fundamental symmetry of nature.

So neat was Wu’s experiment that she also managed to prove that nature broke a second symmetry, called C for charge conjugation. This expresses the idea that if you swap all the particles in an interaction with their antiparticles, the interaction should still happen in the same way. This finding set the stage for physicists to revise their views on other assumed symmetries of nature. ‘CP’, the combination of charge and parity conservation, was proposed to hold , but was then shown to be violated in 1964 — also in decays of kaons.

Also in 1964 came the idea of ‘spontaneous’ symmetry breaking in particle physics, followed in 1967 by the application of this idea to ‘electroweak’ symmetry breaking. Electroweak theory explains how the weak nuclear and electromagnetic forces are unified at high energies, such as those prevalent in the early Universe, but seem to us to be distinct forces mediated by particles of very different masses. Spontaneous symmetry breaking suggested the existence of the Higgs boson — a particle eventually discovered in 2012 at the Large Hadron Collider at CERN, Europe’s particle-physics laboratory near Geneva, Switzerland. Today, asymmetries in decays of kaons and other particles being investigated at CERN and elsewhere might point the way towards new effects beyond the standard model of particle physics.

The ‘Matilda’ effect

The seminal nature of her discovery raises the question of why so few people have heard of Fowler. In most physics departments of her time, gender parity was maximally violated. Powell’s lab was something of an exception. The confluence of war time and a new approach to science had shifted its gender balance. The large amounts of photographic data being gathered meant that Powell had employed teams of scanners, including van der Merwe. These scanners, most of whom were women, painstakingly trawled through the photographs, handing over anything unusual or interesting to one of the physicists for further analysis.

Centenary of particle pioneer

Fowler was not a scanner. She was one of the few women invited to do a physics PhD, after achieving a first-class degree — an exceptional result for anyone especially in those days. Smart and decisive, she took just two days’ holiday, and started work in June 1947. After making her discovery, the first person she told was fellow PhD student Peter Fowler. “We spent a little while looking and thinking and enjoying the moment of discovery. Then I told the others,” she says. The grandson of nuclear pioneer Ernest Rutherford, Peter Fowler was widely regarded as a brilliant young physicist. Three years older than Rosemary , he was a year below her, because his studies had been interrupted by war service. The two married in July 1949.

When I asked Rosemary why she left physics after that, without completing her PhD, I expected a difficult conversation, but her response was pragmatic. Living in a time of food rations, housing shortages and great sacrifice, and with no time-saving appliances or childcare for their three girls, she decided that it would be best for physics if Peter kept working. She would assist him with his work from home, keep the house and raise their children — and having made that decision, that is what she did.

Rosemary’s contribution has, over time and in various publications, often been attributed to her husband or to Powell. There seems to be no maliciousness about this — Powell was meticulous in acknowledging contributions. But it does seem to be a prime example of the ‘Matilda’ effect, the phenomenon that female scientists’ contributions are often overlooked or attributed to their male counterparts.

Rosemary is by no means the only one, even in this story. Powell won the Nobel Prize in Physics in 1950 for the discovery of the pion using the emulsion technique, while the contributions of the technique’s inventor, Austrian physicist Marietta Blau, were overlooked. Evidence for the pion also appeared in Nature papers by Indian physicist Bibha Choudhuri, published during the Second World War 8 ; her work is even less well known than Blau’s. Lee and Yang were awarded the Nobel Prize in Physics in 1957 for their work on parity violation; Wu received no such recognition. Now, 75 years after Rosemary’s discovery and with the long view of its importance in physics, it seems fitting to set her part of the record straight.

Nature 625 , 448-449 (2024)

doi: https://doi.org/10.1038/d41586-024-00109-5

Lattes, C. M. G., Muirhead, H., Occhialini, G. P. S. & Powell, C. F. Nature 159 , 694–697 (1947).

Article   Google Scholar  

Rochester, G. D. & Butler, C. C. Nature 160 , 855–857 (1947).

Article   PubMed   Google Scholar  

Brown, R. et al. Nature 163 , 47–51 (1949).

Brown, R. et al. Nature 163 , 82–87 (1949).

Brown, R. H. et al. Phil. Mag. 40 , 862–881 (1949).

Lee, T. D. & Yang, C. N. Phys. Rev. 104 , 254–258 (1956).

Wu, C. S., Ambler, E., Hayward, R. W., Hoppes, D. D. & Hudson, R. P. Phys. Rev. 105 , 1413–1415 (1957).

Bose, D. M. & Choudhuri, B. Nature 149 , 302 (1942).

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October 1956: Lee and Yang Crack the Mirror of Parity

Until the pair’s explosive paper, physicists assumed that particles would act the same when mirrored..

On a hazy January day in Zurich 65 years ago, Wolfgang Pauli was composing a letter in untidy scrawl to his colleague Victor Weisskopf. He was dubious about a recent proposal, from Tsung-Dao Lee and Chen-Ning Yang a few months earlier, that parity—the basic symmetry between left and right in physical laws—might be violated. Pauli captured his skepticism in an immortal quip: “ Ich glaube aber nicht, daß der Herrgott ein schwacher Linkshänder ist. ” (I do not believe that the Lord is a weak left-hander.)

He wasn’t alone. At the time, physicists believed all the known fundamental forces—electromagnetism, gravity, the strong force, and the weak force—obeyed parity symmetry. Why shouldn’t the universe look the same in the mirror?

But two days later, the elegant mirror of parity was shattered. Initial data from Chien-Shiung Wu’s experiment suggested Lee and Yang’s theory was correct. In a second, frantic note, Pauli wrote: “ Sehr aufregend. Wie sicher ist die Nachricht? ” (Very exciting. How sure is this news?).

Lee and Yang’s “ Question of Parity Conservation in Weak Interactions ,” published October 1, 1956, took the physics community by storm. Their ideas provoked a frenzy of debate and experimentation, which just a year later landed the pair two Nobel medals.

At the time, physicists were plagued by a problem known as the “theta-tau puzzle.” Two particles—now called kaons—appeared to have the same masses and lifetimes, but, somehow, different decays: thetas into two pions, taus into three pions.

Hypotheses proliferated. Some physicists proposed that the particles weren’t identical after all—that tau was a smidge heavier than theta—or that high spin numbers might explain the strange decay. Ironically, Lee and Yang pitched an idea: Tau and theta might point to a new symmetry (ironic, given that their later, Nobel-earning paper argued for a violation of symmetry). Experiments quickly proved all these models wrong.

At a conference in April 1956, Yang discussed the theta-tau puzzle, prompting a debate. At one point, Richard Feynman asked a question of Martin Block’s: “Could it be … that parity is not conserved … does nature have a way of defining right or left-handedness uniquely?” Yang replied that he and Lee had investigated the question but not reached a conclusion.

After the conference, Lee had a breakthrough while speaking with Jack Steinberger, which he recalled during a 2001 talk: “If parity is not conserved in strange particle decays, there could be an asymmetry between events… This is the missing key! ” The conversation led Steinberger and his colleagues to search for parity violation in hyperon decay, but with too little data—just 48 detected particles— their results were inconclusive.

Meanwhile, Lee and Yang began to pore over existing data. “At that time, everyone believed correctly—at least as far as we know now—that parity was conserved in the strong and electromagnetic interactions,” says Allan Franklin, a physics historian at the University of Colorado, Boulder. Had anyone actually confirmed parity in weak interactions? The answer, Lee and Yang realized, was no. (In fact, experiments in the 1930s had already revealed parity violation, but everyone missed it, says Franklin.)

Many physicists were, like Pauli, dubious of parity violation. “Why should nature distinguish between left and right?” Franklin says. Feynman bet against it $50-to-$1, and Felix Bloch told his Stanford colleagues he’d bet his hat. “He later remarked to TD Lee, with whom I also spoke, that he was lucky he didn’t own a hat,” Franklin says.

Doubts aside, experimentalists seized on Lee and Yang’s idea. With advance notice in May 1956, Wu, their colleague at Columbia, dropped all her plans and designed an experiment using decaying cobalt-60. By December, she had enough data to demonstrate parity violation.

When fellow Columbia physicists Leon Lederman and Richard Garwin heard news of Wu’s achievement, they realized they could reconfigure a muon beam to corroborate her result. Late on a Friday night, Lederman, Garwin, and a graduate student named Marcel Weinrich jerry-rigged an experiment using a coffee can, wooden cutting board, and Scotch tape.

“By six o'clock in the morning, we were able to call people and tell them that the laws of parity violate mirror symmetry,” Lederman later recalled . The universe, by a margin of roughly 1 in 10,000, really did prefer left to right.

Both   results were published February 15, 1957, in Physical Review. Despite Wu’s leading role and 26 Nobel nominations, she never received the prize, to the outrage of colleagues like Pauli. Her first recognition for parity violation came over a decade later, with the 1978 Wolf Prize.

The discovery of parity violation set the stage for the discovery of charge-parity (CP) violation, and, arguably, other symmetry-breaking phenomena that led to the foundation of the Standard Model. “The fact that parity itself was violated was just a huge change in the way we think,” Franklin says. For physicists who had treated nature’s symmetries with reverence, it felt like a shocking betrayal.

As Yang said in his Nobel acceptance speech: “This prospect did not appeal to us. Rather we were, so to speak, driven to it through frustration.”

Dan Garisto

Dan Garisto is a science journalist based in New York City.

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Young's Double Slit Experiment

The Original Experiment

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Throughout the nineteenth century, physicists had a consensus that light behaved like a wave, in large part thanks to the famous double slit experiment performed by Thomas Young. Driven by the insights from the experiment, and the wave properties it demonstrated, a century of physicists sought out the medium through which light was waving, the luminous ether . Though the experiment is most notable with light, the fact is that this sort of experiment can be performed with any type of wave, such as water. For the moment, however, we'll focus on the behavior of light.

What Was the Experiment?

In the early 1800s (1801 to 1805, depending on the source), Thomas Young conducted his experiment. He allowed light to pass through a slit in a barrier so it expanded out in wave fronts from that slit as a light source (under Huygens' Principle ). That light, in turn, passed through the pair of slits in another barrier (carefully placed the right distance from the original slit). Each slit, in turn, diffracted the light as if they were also individual sources of light. The light impacted an observation screen. This is shown to the right.

When a single slit was open, it merely impacted the observation screen with greater intensity at the center and then faded as you moved away from the center. There are two possible results of this experiment:

Particle interpretation: If light exists as particles, the intensity of both slits will be the sum of the intensity from the individual slits.

Wave interpretation: If light exists as waves, the light waves will have interference under the principle of superposition , creating bands of light (constructive interference) and dark (destructive interference).

When the experiment was conducted, the light waves did indeed show these interference patterns. A third image that you can view is a graph of the intensity in terms of position, which matches with the predictions from interference.

Impact of Young's Experiment

At the time, this seemed to conclusively prove that light traveled in waves, causing a revitalization in Huygen's wave theory of light, which included an invisible medium, ether , through which the waves propagated. Several experiments throughout the 1800s, most notably the famed Michelson-Morley experiment , attempted to detect the ether or its effects directly.

They all failed and a century later, Einstein's work in the photoelectric effect and relativity resulted in the ether no longer being necessary to explain the behavior of light. Again a particle theory of light took dominance.

Expanding the Double Slit Experiment

Still, once the photon theory of light came about, saying the light moved only in discrete quanta, the question became how these results were possible. Over the years, physicists have taken this basic experiment and explored it in a number of ways.

In the early 1900s, the question remained how light — which was now recognized to travel in particle-like "bundles" of quantized energy, called photons, thanks to Einstein's explanation of the photoelectric effect — could also exhibit the behavior of waves. Certainly, a bunch of water atoms (particles) when acting together form waves. Maybe this was something similar.

One Photon at a Time

It became possible to have a light source that was set up so that it emitted one photon at a time. This would be, literally, like hurling microscopic ball bearings through the slits. By setting up a screen that was sensitive enough to detect a single photon, you could determine whether there were or were not interference patterns in this case.

One way to do this is to have a sensitive film set up and run the experiment over a period of time, then look at the film to see what the pattern of light on the screen is. Just such an experiment was performed and, in fact, it matched Young's version identically — alternating light and dark bands, seemingly resulting from wave interference.

This result both confirms and bewilders the wave theory. In this case, photons are being emitted individually. There is literally no way for wave interference to take place because each photon can only go through a single slit at a time. But the wave interference is observed. How is this possible? Well, the attempt to answer that question has spawned many intriguing interpretations of  quantum physics , from the Copenhagen interpretation to the many-worlds interpretation.

It Gets Even Stranger

Now assume that you conduct the same experiment, with one change. You place a detector that can tell whether or not the photon passes through a given slit. If we know the photon passes through one slit, then it cannot pass through the other slit to interfere with itself.

It turns out that when you add the detector, the bands disappear. You perform the exact same experiment, but only add a simple measurement at an earlier phase, and the result of the experiment changes drastically.

Something about the act of measuring which slit is used removed the wave element completely. At this point, the photons acted exactly as we'd expect a particle to behave. The very uncertainty in position is related, somehow, to the manifestation of wave effects.

More Particles

Over the years, the experiment has been conducted in a number of different ways. In 1961, Claus Jonsson performed the experiment with electrons, and it conformed with Young's behavior, creating interference patterns on the observation screen. Jonsson's version of the experiment was voted "the most beautiful experiment" by  Physics World  readers in 2002.

In 1974, technology became able to perform the experiment by releasing a single electron at a time. Again, the interference patterns showed up. But when a detector is placed at the slit, the interference once again disappears. The experiment was again performed in 1989 by a Japanese team that was able to use much more refined equipment.

The experiment has been performed with photons, electrons, and atoms, and each time the same result becomes obvious — something about measuring the position of the particle at the slit removes the wave behavior. Many theories exist to explain why, but so far much of it is still conjecture.

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• Heinrich Hertz, Scientist Who Proved Existence of Electromagnetic Waves
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Wave Optics

Young’s double slit experiment, learning objectives.

By the end of this section, you will be able to:

• Explain the phenomena of interference.
• Define constructive interference for a double slit and destructive interference for a double slit.

Although Christiaan Huygens thought that light was a wave, Isaac Newton did not. Newton felt that there were other explanations for color, and for the interference and diffraction effects that were observable at the time. Owing to Newton’s tremendous stature, his view generally prevailed. The fact that Huygens’s principle worked was not considered evidence that was direct enough to prove that light is a wave. The acceptance of the wave character of light came many years later when, in 1801, the English physicist and physician Thomas Young (1773–1829) did his now-classic double slit experiment (see Figure 1).

Figure 1. Young’s double slit experiment. Here pure-wavelength light sent through a pair of vertical slits is diffracted into a pattern on the screen of numerous vertical lines spread out horizontally. Without diffraction and interference, the light would simply make two lines on the screen.

Why do we not ordinarily observe wave behavior for light, such as observed in Young’s double slit experiment? First, light must interact with something small, such as the closely spaced slits used by Young, to show pronounced wave effects. Furthermore, Young first passed light from a single source (the Sun) through a single slit to make the light somewhat coherent. By coherent , we mean waves are in phase or have a definite phase relationship. Incoherent means the waves have random phase relationships. Why did Young then pass the light through a double slit? The answer to this question is that two slits provide two coherent light sources that then interfere constructively or destructively. Young used sunlight, where each wavelength forms its own pattern, making the effect more difficult to see. We illustrate the double slit experiment with monochromatic (single λ ) light to clarify the effect. Figure 2 shows the pure constructive and destructive interference of two waves having the same wavelength and amplitude.

Figure 2. The amplitudes of waves add. (a) Pure constructive interference is obtained when identical waves are in phase. (b) Pure destructive interference occurs when identical waves are exactly out of phase, or shifted by half a wavelength.

When light passes through narrow slits, it is diffracted into semicircular waves, as shown in Figure 3a. Pure constructive interference occurs where the waves are crest to crest or trough to trough. Pure destructive interference occurs where they are crest to trough. The light must fall on a screen and be scattered into our eyes for us to see the pattern. An analogous pattern for water waves is shown in Figure 3b. Note that regions of constructive and destructive interference move out from the slits at well-defined angles to the original beam. These angles depend on wavelength and the distance between the slits, as we shall see below.

Figure 3. Double slits produce two coherent sources of waves that interfere. (a) Light spreads out (diffracts) from each slit, because the slits are narrow. These waves overlap and interfere constructively (bright lines) and destructively (dark regions). We can only see this if the light falls onto a screen and is scattered into our eyes. (b) Double slit interference pattern for water waves are nearly identical to that for light. Wave action is greatest in regions of constructive interference and least in regions of destructive interference. (c) When light that has passed through double slits falls on a screen, we see a pattern such as this. (credit: PASCO)

To understand the double slit interference pattern, we consider how two waves travel from the slits to the screen, as illustrated in Figure 4. Each slit is a different distance from a given point on the screen. Thus different numbers of wavelengths fit into each path. Waves start out from the slits in phase (crest to crest), but they may end up out of phase (crest to trough) at the screen if the paths differ in length by half a wavelength, interfering destructively as shown in Figure 4a. If the paths differ by a whole wavelength, then the waves arrive in phase (crest to crest) at the screen, interfering constructively as shown in Figure 4b. More generally, if the paths taken by the two waves differ by any half-integral number of wavelengths [(1/2) λ , (3/2) λ , (5/2) λ , etc.], then destructive interference occurs. Similarly, if the paths taken by the two waves differ by any integral number of wavelengths ( λ , 2 λ , 3 λ , etc.), then constructive interference occurs.

Figure 4. Waves follow different paths from the slits to a common point on a screen. (a) Destructive interference occurs here, because one path is a half wavelength longer than the other. The waves start in phase but arrive out of phase. (b) Constructive interference occurs here because one path is a whole wavelength longer than the other. The waves start out and arrive in phase.

Take-Home Experiment: Using Fingers as Slits

Look at a light, such as a street lamp or incandescent bulb, through the narrow gap between two fingers held close together. What type of pattern do you see? How does it change when you allow the fingers to move a little farther apart? Is it more distinct for a monochromatic source, such as the yellow light from a sodium vapor lamp, than for an incandescent bulb?

Figure 5. The paths from each slit to a common point on the screen differ by an amount dsinθ, assuming the distance to the screen is much greater than the distance between slits (not to scale here).

Figure 5 shows how to determine the path length difference for waves traveling from two slits to a common point on a screen. If the screen is a large distance away compared with the distance between the slits, then the angle θ between the path and a line from the slits to the screen (see the figure) is nearly the same for each path. The difference between the paths is shown in the figure; simple trigonometry shows it to be d sin  θ , where d is the distance between the slits. To obtain constructive interference for a double slit , the path length difference must be an integral multiple of the wavelength, or  d sin  θ = mλ, for   m = 0, 1, −1, 2, −2, . . . (constructive).

Similarly, to obtain destructive interference for a double slit , the path length difference must be a half-integral multiple of the wavelength, or

[latex]d\sin\theta=\left(m+\frac{1}{2}\right)\lambda\text{, for }m=0,1,-1,2,-2,\dots\text{ (destructive)}\\[/latex],

where λ is the wavelength of the light, d is the distance between slits, and θ is the angle from the original direction of the beam as discussed above. We call m the order of the interference. For example, m  = 4 is fourth-order interference.

The equations for double slit interference imply that a series of bright and dark lines are formed. For vertical slits, the light spreads out horizontally on either side of the incident beam into a pattern called interference fringes, illustrated in Figure 6. The intensity of the bright fringes falls off on either side, being brightest at the center. The closer the slits are, the more is the spreading of the bright fringes. We can see this by examining the equation  d sin  θ = mλ, for   m = 0, 1, −1, 2, −2, . . . .

For fixed λ and m , the smaller d is, the larger θ must be, since [latex]\sin\theta=\frac{m\lambda}{d}\\[/latex]. This is consistent with our contention that wave effects are most noticeable when the object the wave encounters (here, slits a distance d apart) is small. Small d gives large θ , hence a large effect.

Figure 6. The interference pattern for a double slit has an intensity that falls off with angle. The photograph shows multiple bright and dark lines, or fringes, formed by light passing through a double slit.

Example 1. Finding a Wavelength from an Interference Pattern

Suppose you pass light from a He-Ne laser through two slits separated by 0.0100 mm and find that the third bright line on a screen is formed at an angle of 10.95º relative to the incident beam. What is the wavelength of the light?

The third bright line is due to third-order constructive interference, which means that m  = 3. We are given d = 0.0100 mm and θ  = 10.95º. The wavelength can thus be found using the equation  d sin  θ = mλ  for constructive interference.

The equation is d sin  θ = mλ . Solving for the wavelength λ gives [latex]\lambda=\frac{d\sin\theta}{m}\\[/latex].

Substituting known values yields

[latex]\begin{array}{lll}\lambda&=&\frac{\left(0.0100\text{ nm}\right)\left(\sin10.95^{\circ}\right)}{3}\\\text{ }&=&6.33\times10^{-4}\text{ nm}=633\text{ nm}\end{array}\\[/latex]

To three digits, this is the wavelength of light emitted by the common He-Ne laser. Not by coincidence, this red color is similar to that emitted by neon lights. More important, however, is the fact that interference patterns can be used to measure wavelength. Young did this for visible wavelengths. This analytical technique is still widely used to measure electromagnetic spectra. For a given order, the angle for constructive interference increases with λ , so that spectra (measurements of intensity versus wavelength) can be obtained.

Example 2. Calculating Highest Order Possible

Interference patterns do not have an infinite number of lines, since there is a limit to how big m can be. What is the highest-order constructive interference possible with the system described in the preceding example?

Strategy and Concept

The equation  d sin  θ = mλ ( for   m = 0, 1, −1, 2, −2, . . . ) describes constructive interference. For fixed values of d and λ , the larger m is, the larger sin  θ  is. However, the maximum value that sin  θ  can have is 1, for an angle of 90º. (Larger angles imply that light goes backward and does not reach the screen at all.) Let us find which m corresponds to this maximum diffraction angle.

Solving the equation  d sin  θ = mλ  for m gives [latex]\lambda=\frac{d\sin\theta}{m}\\[/latex].

Taking sin  θ = 1 and substituting the values of d and λ from the preceding example gives

[latex]\displaystyle{m}=\frac{\left(0.0100\text{ mm}\right)\left(1\right)}{633\text{ nm}}\approx15.8\\[/latex]

Therefore, the largest integer m can be is 15, or  m  = 15.

The number of fringes depends on the wavelength and slit separation. The number of fringes will be very large for large slit separations. However, if the slit separation becomes much greater than the wavelength, the intensity of the interference pattern changes so that the screen has two bright lines cast by the slits, as expected when light behaves like a ray. We also note that the fringes get fainter further away from the center. Consequently, not all 15 fringes may be observable.

Section Summary

• Young’s double slit experiment gave definitive proof of the wave character of light.
• An interference pattern is obtained by the superposition of light from two slits.
• There is constructive interference when  d sin  θ = mλ ( for   m = 0, 1, −1, 2, −2, . . . ), where d  is the distance between the slits, θ is the angle relative to the incident direction, and m  is the order of the interference.
• There is destructive interference when  d sin  θ = mλ ( for   m = 0, 1, −1, 2, −2, . . . ).

Conceptual Questions

• Young’s double slit experiment breaks a single light beam into two sources. Would the same pattern be obtained for two independent sources of light, such as the headlights of a distant car? Explain.
• Suppose you use the same double slit to perform Young’s double slit experiment in air and then repeat the experiment in water. Do the angles to the same parts of the interference pattern get larger or smaller? Does the color of the light change? Explain.
• Is it possible to create a situation in which there is only destructive interference? Explain.
• Figure 7 shows the central part of the interference pattern for a pure wavelength of red light projected onto a double slit. The pattern is actually a combination of single slit and double slit interference. Note that the bright spots are evenly spaced. Is this a double slit or single slit characteristic? Note that some of the bright spots are dim on either side of the center. Is this a single slit or double slit characteristic? Which is smaller, the slit width or the separation between slits? Explain your responses.

Figure 7. This double slit interference pattern also shows signs of single slit interference. (credit: PASCO)

Problems & Exercises

• At what angle is the first-order maximum for 450-nm wavelength blue light falling on double slits separated by 0.0500 mm?
• Calculate the angle for the third-order maximum of 580-nm wavelength yellow light falling on double slits separated by 0.100 mm.
• What is the separation between two slits for which 610-nm orange light has its first maximum at an angle of 30.0º?
• Find the distance between two slits that produces the first minimum for 410-nm violet light at an angle of 45.0º.
• Calculate the wavelength of light that has its third minimum at an angle of 30.0º when falling on double slits separated by 3.00 μm.
• What is the wavelength of light falling on double slits separated by 2.00 μm if the third-order maximum is at an angle of 60.0º?
• At what angle is the fourth-order maximum for the situation in Question 1?
• What is the highest-order maximum for 400-nm light falling on double slits separated by 25.0 μm?
• Find the largest wavelength of light falling on double slits separated by 1.20 μm for which there is a first-order maximum. Is this in the visible part of the spectrum?
• What is the smallest separation between two slits that will produce a second-order maximum for 720-nm red light?
• (a) What is the smallest separation between two slits that will produce a second-order maximum for any visible light? (b) For all visible light?
• (a) If the first-order maximum for pure-wavelength light falling on a double slit is at an angle of 10.0º, at what angle is the second-order maximum? (b) What is the angle of the first minimum? (c) What is the highest-order maximum possible here?

Figure 8. The distance between adjacent fringes is [latex]\Delta{y}=\frac{x\lambda}{d}\\[/latex], assuming the slit separation d  is large compared with λ .

• Using the result of the problem above, calculate the distance between fringes for 633-nm light falling on double slits separated by 0.0800 mm, located 3.00 m from a screen as in Figure 8.
• Using the result of the problem two problems prior, find the wavelength of light that produces fringes 7.50 mm apart on a screen 2.00 m from double slits separated by 0.120 mm (see Figure 8).

coherent:  waves are in phase or have a definite phase relationship

constructive interference for a double slit:  the path length difference must be an integral multiple of the wavelength

destructive interference for a double slit:  the path length difference must be a half-integral multiple of the wavelength

incoherent:  waves have random phase relationships

order:  the integer m  used in the equations for constructive and destructive interference for a double slit

Selected Solutions to Problems & Exercises

3. 1.22 × 10 −6 m

9. 1200 nm (not visible)

11. (a) 760 nm; (b) 1520 nm

13. For small angles sin θ − tan θ  ≈ θ  (in radians).

For two adjacent fringes we have,  d  sin θ m = mλ  and  d sin θ m + 1 = ( m  + 1) λ

Subtracting these equations gives

[latex]\begin{array}{}d\left(\sin{\theta }_{\text{m}+1}-\sin{\theta }_{\text{m}}\right)=\left[\left(m+1\right)-m\right]\lambda \\ d\left({\theta }_{\text{m}+1}-{\theta }_{\text{m}}\right)=\lambda \\ \text{tan}{\theta }_{\text{m}}=\frac{{y}_{\text{m}}}{x}\approx {\theta }_{\text{m}}\Rightarrow d\left(\frac{{y}_{\text{m}+1}}{x}-\frac{{y}_{\text{m}}}{x}\right)=\lambda \\ d\frac{\Delta y}{x}=\lambda \Rightarrow \Delta y=\frac{\mathrm{x\lambda }}{d}\end{array}\\[/latex]

• College Physics. Authored by : OpenStax College. Located at : http://cnx.org/contents/031da8d3-b525-429c-80cf-6c8ed997733a/College_Physics . License : CC BY: Attribution . License Terms : Located at License

The Wu Experiment

• First Online: 25 September 2022

Cite this chapter

• Ronald Laymon 3 &
• Allan Franklin 4  

Part of the book series: Synthesis Lectures on Engineering, Science, and Technology ((SLEST))

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In the 1950s the physics community was confronted with the θ − τ puzzle. There were two elementary particles the θ and the τ that on one set of criteria, mass and lifetime, seemed to be the same particle. On a second set of criteria, spin and parity, they were different. The puzzle resisted solution using then accepted physics. T. D. Lee and C. N. Yang proposed a radical solution, parity was not conserved in the weak interactions. Their hypothesis was thought to be sufficiently plausible to merit further investigation. Lee and Yang proposed several experimental tests of their hypothesis, one of which was to investigate any possible asymmetry in the β decay of oriented nuclei. This experiment was performed by C. S. Wu and her collaborators and clearly demonstrated parity nonconservation. (The results were reported in February 1957 and Lee and Yang were awarded the Nobel Prize in Physics later that year.) The Wu result was sufficient to justify acceptance of parity nonconservation, but because it did not measure the asymmetry parameter with sufficient precision it also justified further experimental pursuit.

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For the proof of the theorem see Gibson and Pollard ( 1976 , pp. 119–127, 160–162).

For more details and the theoretical support for these parity determinations (including the role of the L 1  +  L 2 superscript) see Gibson and Pollard ( 1976 , pp. 159–160).

For the current status of the puzzle see Bellantoni ( 2016 ).

This reference contains a reprint of a 1983 lecture by Wu.

See Wu ( 2008 , pp. 55–56) for just how difficult this turned out to be.

David Christen (Oak Ridge National Laboratory) informs us that the current product of choice used to secure wayward components when conducting experiments near absolute zero is waxed dental floss. It behaves exactly as you’d want.

Note however that we have simplified insofar as we have made use of only two dimensions.

It is important to keep in mind that this analysis does not assume that the β emissions are themselves polarized, only that the Co 60 source is. It was only later determined that β emissions are in fact longitudinally polarized which is by itself a counterexample to parity conservation. This because in the case of a longitudinally polarized beam of β emissions, parity is violated in very much the same way that it was violated in the case of the Wu experiment, namely, that spin direction remains intact after the parity transformation while all else changes.

A handy and frequently used way of stating the lack of congruence is that the pseudo-scalar ( S  ⋅  p ) changes in value, where the vector S represents spin and p the momentum of the system.

We note here that while Wu does not explicitly state that in this case the horizontal field was turned on, we think that is implicit in the argument. This is indicated by the fact that the third systematic check dealt with the case of where there was in effect no cooling but there was a vertical polarizing field. Hence, it’s natural that the fourth systematic check would deal with the case where there was cooling (produced by the horizontal field) but no polarization produced by a vertical field.

For some background information on the Friedman and Telegdi experiment and the publication of its results see Goudsmit ( 1971 ).

Bellantoni, L. (2016). Theta and tau, two generations later. Fermi News . Available from: https://news.fnal.gov/2016/04/theta-tau-two-generations-later/

Bernstein, J. (1967). A comprehensible world . Random House.

Google Scholar  

Chirovsky, L. M., Lee, W. P., Sabbas, A. M., Groves, J. L., & Wu, C. S. (1980). Directional distributions of beta-rays emitted from polarized 60 Co nuclei. Physics Letters, 94B , 127–130.

Article   ADS   Google Scholar  

Ellis, C. D., & Wooster, W. A. (1927). The average energy of disintegration of radium E. Proceedings of the Royal Society (London) A, 117 , 109–123.

Feynman, R. P. (1985). Surely you're joking, Mr. Feynman . Norton.

Friedman, J. L., & Telegdi, V. L. (1957). Nuclear emulsion evidence for parity nonconservation in the decay chain π + − μ + − e + . Physical Review, 105 , 1681–1682.

Garwin, R. L., & Lederman, L. M. (1997). History of parity violation experiment. Nature, 386 , 542–543.

Article   Google Scholar  

Garwin, R. L., Lederman, L. M., et al. (1957). Observation of the failure of conservation of parity and charge conjugation in meson decays: The magnetic moment of the free muon. Physical Review, 105 , 1415–1417.

Gibson, W. M., & Pollard, B. R. (1976). Symmetry principles in elementary particle physics . Cambridge University Press.

Goudsmit, S. A. (1971). A reply from the Editor of Physical Review. Adventures in Experimental Physics Gamma, 137 .

Hudson, R. P. (2016). The reversal of the parity law in nuclear physics . National Institute of Standards and Technology. Available from: https://www.nist.gov/pml/fall-parity/reversal-parity-law-nuclear-physics

Lee, T.D. (1985). Letter . A. Franklin.

Lee, T. D., & Yang, C. N. (1956). Question of parity nonconservation in weak interactions. Physical Review, 104 , 254–258.

Wu, C. S. (2008). The discovery of the parity violation in weak interactions and its recent developments. Lecture Notes in Physics, 746 , 43–69.

Wu, C. S., Ambler, E., Hoppes, D. D., & Hudson, R. P. (1957). Experimental test of parity nonconservation in beta decay. Physical Review, 105 , 1413–1415.

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Laymon, R., Franklin, A. (2022). The Wu Experiment. In: Case Studies in Experimental Physics. Synthesis Lectures on Engineering, Science, and Technology. Springer, Cham. https://doi.org/10.1007/978-3-031-12608-6_3

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Young's Experiment

• Anatomy of a Two-Point Source Interference Pattern
• The Path Difference
• Young's Equation
• Young's Experiment
• Other Applications of Two-Point Source Interference

Today's classroom version of the same experiment is typically performed using a laser beam as the source. Rather than using a note card to split the single beam into two coherent beams, a carbon-coated glass slide with two closely spaced etched slits is used. The slide with its slits is most commonly purchased from a manufacturer who provides a measured value for the slit separation distance - the d value in Young's equation. Light from the laser beam diffracts through the slits and emerges as two separate coherent waves. The interference pattern is then projected onto a screen where reliable measurements can be made of L and y for a given bright spot with order value m . Knowing these four values allows a student to determine the value of the wavelength of the original light source.

To illustrate some typical results from this experiment and the subsequent analysis, consider the sample data provided below for d, y, L and m.

(Note: AN 0 = central antinode and AN 4 = fourth antinode)  

The determination of the wavelength demands that the above values for d, y, L and m be substituted into Young's equation.

Careful inspection of the units of measurement is always advisable. The sample data here reveal that each measured quantity is recorded with a different unit. Before substituting these measured values into the above equation, it is important to give some thought to the treatment of units. One means of resolving the issue of nonuniform units is to simply pick a unit of length and to convert all quantities to that unit. If doing so, one might want to pick a unit that one of the data values already has so that there is one less conversion. A wise choice is to choose the meter as the unit to which all other measured values are converted. Since there are 1000 millimeters in 1 meter, the 0.250 mm is equivalent to 0.000250 meter. And since there are 100 centimeters in 1 meter, the 10.2 cm is equivalent to 0.102 m. Thus, the new values of d, y and L are:

While the conversion of all the data to the same unit is not the only means of treating such measured values, it might be the most advisable - particularly for those students who are less at ease with such conversions.

Now that the issue regarding the units of measurement has been resolved, substitution of the measured values into Young's equation can be performed.

λ  = 6.52 x 10 -7 m

As is evident here, the wavelength of visible light is rather small. For this reason wavelength is often expressed using the unit nanometer, where 1 meter is equivalent to 10 9 nanometers. Multiplying by 10 9 will convert the wavelength from meters to nanometers (abbreviated nm).

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Check Your Understanding

1. The diagram below depicts the results of Young's Experiment. The appropriate measurements are listed on the diagram. Use these measurements to determine the wavelength of light in nanometers. (GIVEN: 1 meter = 10 9 nanometers)

Answer: 657 nm

First, identify known values in terms of their corresponding variable symbol:

L = 10.2 m = 1020 cm y = 22.5 cm m = 10 d = 0.298 mm = 0.0298 cm

(Note: m was chosen as 10 since the y distance corresponds to the distance from the 5th bright band on one side of the central band and the 5th bright band on the other side of the central band.)

Then convert all known values to an identical unit. In this case, cm has been chosen as the unit to use. The converted values are listed in the table above.

Substitute all values into Young's equation and perform calculation of the wavelength. The unit of wavelength is cm.

λ = y • d / ( m • L) λ = ( 22.5 cm ) • ( 0.0298 cm ) / [ ( 10 ) • ( 1020 cm ) ] λ = 6.57 x 10 -5 cm

Finally convert to nanometers using a conversion factor. If there are 10 9 nm in 1 meter, then there must be 10 7 nm in the smaller centimeter.

λ = ( 6.57 x 10 -5 cm ) • ( 10 7 nm / 1 cm ) = 657 nm

2. A student uses a laser and a double-slit apparatus to project a two-point source light interference pattern onto a whiteboard located 5.87 meters away. The distance measured between the central bright band and the fourth bright band is 8.21 cm. The slits are separated by a distance of 0.150 mm. What would be the measured wavelength of light?

Answer: 524 nm

L = 5.87 m = 587 cm y = 8.21 cm m = 4 d = 0.150 mm = 0.0150 cm

λ = y • d / ( m • L) λ = ( 8.21 cm ) • ( 0.0150 cm ) / [ ( 4 ) • ( 587 cm ) ] λ = 5.24 x 10 -5 cm

λ = ( 5.24 x 10 -5 cm ) • ( 10 7 nm / 1 cm ) = 524 nm

3. The analysis of any two-point source interference pattern and a successful determination of wavelength demands an ability to sort through the measured information and equating the values with the symbols in Young's equation. Apply your understanding by interpreting the following statements and identifying the values of y, d, m and L. Finally, perform some conversions of the given information such that all information share the same unit.

This question simply asks to equate the stated information with the variables of Young's equation and to perform conversions such that all information is in the same unit.

(Note that m = 4.5 represents the fifth nodal position or dark band from the central bright band. Also note that the given values have been converted to cm.)

b. An interference pattern is produced when light is incident upon two slits that are 50.0 micrometers apart. The perpendicular distance from the midpoint between the slits to the screen is 7.65 m. The distance between the two third-order antinodes on opposite sides of the pattern is 32.9 cm.

This question simply asks to equate the stated information with the variables of Young's equation and to perform conversions such that all information is in the same unit. 

(Note that m = 6 corresponds to six spacings. There are three spacings between the central antinode and the third antinode. The stated distance is twice as far so the m value must be doubled. Also note that the given values have been converted to cm. There are 10 6 µm in one meter; so there are 10 4 µm in one centimeter.)

c. The fourth nodal line on an interference pattern is 8.4 cm from the first antinodal line when the screen is placed 235 cm from the slits. The slits are separated by 0.25 mm.

 ( Note that the fourth nodal line is assigned the order value of 3.5. Also note that the given values have been converted to cm.)

d. Two sources separated by 0.500 mm produce an interference pattern 525 cm away. The fifth and the second antinodal line on the same side of the pattern are separated by 98 mm.

  ( Note that there are three spacings between the second and the fifth bright bands. Since all spacings are the same distance apart, the distance between the second and the fifth bright bands would be the same as the distance between the central and the third bright bands. Thus, m = 3. Also note that the given values have been converted to cm.)

e. Two slits that are 0.200 mm apart produce an interference pattern on a screen such that the central maximum and the 10th bright band are distanced by an amount equal to one-tenth the distance from the slits to the screen.

 ( Note that there are 10 spacings between the central anti-node and the tenth bright band or tenth anti-node. And observe that they do not state the actual values of L and y; the value of y is expressed in terms of L. )

f. The fifth antinodal line and the second nodal line on the opposite side of an interference pattern are separated by a distance of 32.1 cm when the slits are 6.5 m from the screen. The slits are separated by 25.0 micrometers.

 ( Note that there are five spacings between the central anti-node and the fifth anti-node. And there are 1.5 spacings from the central anti-node in the opposite direction out to the second nodal line. Thus, m = 6.5. Also note that the given values have been converted to cm. There are 10 6 µm in one meter; so there are 10 4 µm in one centimeter.)

g. If two slits 0.100 mm apart are separated from a screen by a distance of 300 mm, then the first-order minimum will be 1 cm from the central maximum.

  ( Note that a the first-order minimum is a point of minimum brightness or a nodal position. The first-order minimum is the first nodal position and is thus the m = 0.5 node. Also note that the given values have been converted to cm. )

h. Consecutive bright bands on an interference pattern are 3.5 cm apart when the slide containing the slits is 10.0 m from the screen. The slit separation distance is 0.050 mm.

   ( Note that the spacing between adjacent bands is given. This distance is equivalent with the distance from the central bright band to the first antinode. Thus, m = 1. Also note that the given values have been converted to cm. )

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Young’s experiment

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• Physics LibreTexts - Young’s Double Slit Experiment
• Florida State University - Molecular Expressions Cell Biology - Thomas Young's Double Slit Experiment
• Khan Academy - Young's double slit introduction
• University of New South Wales - Physclips - Young's experiment
• The University of Texas at Austin - Young's Double-Slit Experiment
• University of Maryland - Department of Physics - The double-slit experiment
• University of Central Florida Pressbooks - Young’s Double Slit Experiment

Young’s experiment , classical investigation into the nature of light, an investigation that provided the basic element in the development of the wave theory and was first performed by the English physicist and physician Thomas Young in 1801. In this experiment, Young identified the phenomenon called interference . Observing that when light from a single source is split into two beams , and the two beams are then recombined, the combined beam shows a pattern of light and dark fringes, Young concluded that the fringes result from the fact that when the beams recombine their peaks and troughs may not be in phase (in step). When two peaks coincide they reinforce each other, and a line of light results; when a peak and a trough coincide they cancel each other, and a dark line results. English scientists did not accept Young’s wave theory until the work of the French physicists François Arago and Augustin-Jean Frésnel had confirmed it many years later.

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Trending Topics

Follow our news, recent searches, southeast asian countries turn to the netherlands for ways to tackle flood risks, advertisement.

The Dutch's experiments with floating buildings and coastal protection can serve to guide Southeast Asia’s bid to battle rising tides.

The Maeslantkering, or Maeslant Barrier, is giant sea gate that serves as the first line of defence for the city of Rotterdam. (Photo: Dutch Ministry of Infrastructure and Water Management)

This audio is generated by an AI tool.

Melissa Goh

Calvin Yang

ROTTERDAM: Some countries in the Southeast Asian region are turning to the Netherlands for ways to tackle rising tides and floods stemming from climate change .   The Dutch, which have decades of expertise in water management, hope to help reduce billions of dollars in costs spent on flood disaster systems and losses suffered by those affected.   Observers said the country’s experiments with floating buildings and coastal protection can help guide Southeast Asia’s bid to battle sea level rise . 

NETHERLANDS’ FLOOD DEFENCE SYSTEM

Among the innovations used in the Netherlands is the Maeslant storm surge barrier located near the Port of Rotterdam, which has been guarding the southern coast for over 25 years.    The fully automated barrier shuts down on its own when the sea level rises above 1.5m, protecting the country where 40 per cent lies below sea level.   In 1991, it cost the Dutch government almost €500 million (US$540 million) to build the storm surge barrier, and another €10 million a year to maintain the structure.   The barrier forms part of the Netherlands' massive flood defence system to protect the low-lying delta region, where most of the Dutch population and economic activities lie.    The only other similar storm surge barrier in the world is in the Russian city of Saint Petersburg.    “The biggest concern is that our country is now 40 per cent floodable,” said Peter Persoon, technical information officer at the Keringhuis Public Water Center.   Preparations have led to the Netherlands being able to resist floods that are at most 5m above normal sea levels, he added.

“When sea levels increase, we have to adjust systems. It's okay for now, but you have to look out for the future. We are already planning what that will be for the year 2100.”   Despite the extensive network of dykes and dams as well as dunes along the coast, the Dutch flood defence system will not be able to withstand the tide if sea level continues to rise, he added. 

“Even in our tiny country, we have to adjust 2000km of dykes, dams and dunes for the future.” 

Commentary: The urgency of addressing rising sea levels in Singapore

Singapore's mean sea level may rise by up to 1.15m by 2100, exceeding previous estimates

Asean's coastal settlements at risk.

Researchers are urging countries to take action to address flooding caused by unavoidable sea level rise.   In particular, Southeast Asia is at serious risk of losing infrastructure and low-lying coastal settlements.   “People think with climate change and sea level rise that they have plenty of time,” said Tjitte Nauta, regional manager for Asia and Oceania at Dutch applied knowledge institute Deltares.    “But this is the time to study it and to make the right decision. I would encourage ASEAN (the Association of Southeast Asian Nations) to move towards, indeed, more awareness, but also collaboration within the region. They can learn from each other, we can also learn from them.”   Thailand, Laos, Vietnam, Indonesia, and Malaysia are hotspots prone to flooding and coastal erosion.   “The whole city of Bangkok is extremely vulnerable,” said Nauta. “If 2m of relative sea level rise, some 28 per cent of the Thai population and 52 per cent of the GDP (gross domestic product) will be affected.    “So for Thailand, it should be very obvious to work on a long-term plan whether they make decisions of protecting the city or moving the city or whatever, but a study should already be there.”   In Indonesia, sea level rise has a profound negative impact on large swathes of low-lying peatland used for oil palm production. 

Similarly in Vietnam, where agricultural output is important in the Mekong and Red River Delta, a 2m sea level rise will have a devastating effect on its people.

Malaysia’s coastal areas will not be spared either, according to satellite data.

Recently, Deltares set up an online platform and invited young diplomats from ASEAN to share their views on tackling climate issues.   “It’s very important to look at what the countries need, instead of us telling them you should do what we think you need to do,” said Josien Grashof, adviser on resilience and planning at Deltares.    “So by getting their ownership of this process, we can really work towards their highest priorities.”

Deltares highlighted problems plaguing some Southeast Asian countries, including the lack of funding and credible data for early warning systems, and differences in national priorities.

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