Tag Archives: quantum theory

The Quantum Physicist as Causal Detective: an Oct. 7, 2020 event

I love mysteries and am quite interested in the nature of reality (you, too?) and that gives us something in common with a couple of Perimeter Institute for Theoretical Physics (PI; Canada) researchers. From The Quantum Physicist as Causal Detective event page on the insidetheperimeter.ca website (notice received via email),

In their live webcast from Perimeter on October 7 [2020], Robert Spekkens and Elie Wolfe will shed light on the exciting possibilities brought about by applying quantum thinking to the science of cause and effect.

Watch the live webcast on this page on Wednesday, October 7 [2020] at 7 pm ET.

What do data science and the foundations of quantum theory have to do with one another?

A great deal, it turns out. The particular branch of data science known as causal inference focuses on a problem which is central to disciplines ranging from epidemiology to economics: that of disentangling correlation and causation in statistical data.

Meanwhile, in a slightly different guise, this same problem has been pondered by quantum physicists as part of a continuing effort to make sense of various puzzling quantum phenomena. On top of that, the most celebrated result concerning quantum theory’s meaning for the nature of reality – Bell’s theorem – can be seen in retrospect to be built on the solution to a particularly challenging problem in causal inference.

Recent efforts to elaborate upon these connections have led to an exciting flow of techniques and insights across the disciplinary divide.

Perimeter researchers Robert Spekkens and Elie Wolfe have done pioneering work studying relations of cause and effect through a quantum foundational lens, and can be counted among a small number of physicists worldwide with expertise in this field.

In their joint webcast from Perimeter [at 7 pm ET] on October 7 [2020], Spekkens and Wolfe will explore what is happening at the intersection of these two fields and how thinking like a quantum physicist leads to new ways of sussing out cause and effect from correlation patterns in statistical data.

For those of us on the West Coast, that webcast will be at 4 p.m. on Wednesday, Oct. 7, 2020 and I believe you can watch it here.

A mathematical sculptor, a live webcast (May 6, 2020) with theoretical cosmologist and author Katie Mack, & uniting quantum theory with Einstein’s Theory of General Relativity in a drawing

I’ve bookended information about the talk with physicist Katie Mack at Canada’s Perimeter Institute on May 6, 2020 with two items on visual art and mathematics and the sciences.

Mathematical sculpting

Robert Fathauer’s Three-Fold Hyperbolic Form exhibits negative curvature, a concept in geometry and topology that describes a surface curving in two directions at every point. Hemp crochet by Marla Peterson. Image courtesy of Robert Fathauer. [downloaded from https://www.pnas.org/content/114/26/6643.full]

You’ll find this image and a few more in a fascinating 2017 paper (see link and citation below) about mathematical sculpture,

Ferguson [Helaman Ferguson], who holds a doctorate in mathematics, never chose between art and science: now nearly 77 years old, he’s a mathematical sculptor. Working in stone and bronze, Ferguson creates sculptures, often placed on college campuses, that turn deep mathematical ideas into solid objects that anyone—seasoned professors, curious children, wayward mathophobes—can experience for themselves.

Mathematics has an intrinsic aesthetic—proofs are often described as “beautiful” or “elegant”—that can be difficult for mathematicians to communicate to outsiders, says Ferguson. “It isn’t something you can tell somebody about on the street,” he says. “But if I hand them a sculpture, they’re immediately relating to it.” Sculpture, he says, can tell a story about math in an accessible language.

Here’s a link to and a citation for the paper,

Science and Culture: Armed with a knack for patterns and symmetry, mathematical sculptors create compelling forms by Stephen Ornes. PNAS [Proceedings of the National Academy of Sciences] June 27, 2017 114 (26) 6643-6645; https://doi.org/10.1073/pnas.1706987114

This paper appears to be open access.

Live webcast: theoretical cosmologist & science communicator Katie Mack

The live webcast will take place at 4 pm PT (1600 hours) on Wednesday, May 6, 2020. Here’s more about Katie Mack and the webcast from the event webpage (click through to the event page to get to the webcast) on the Perimeter Institute of Theoretical Physics (PI) website,

In a special live webcast on May 6 [2020] at 7 pm ET [4 pm PT], theoretical cosmologist and science communicator Katie Mack — known to her many Twitter followers as @astrokatie — will answer questions about her favourite subject: the end of the universe.

Mack, who holds a Simons Emmy Noether Visiting Fellowship at Perimeter, will give viewers a sneak peek at her upcoming book, The End of Everything (Astrophysically Speaking). She will then participate in a live “ask me anything” session, answering questions submitted via social media using the hashtag #piLIVE.

Mack is an Assistant Professor at North Carolina State University whose research investigates dark matter, vacuum decay, and the epoch of reionization. Mack is a popular science communicator on social media, and has contributed to Scientific American, Slate, Sky & Telescope, Time, and Cosmos.

PI is located in Waterloo, Ontario, Canada.

Uniting quantum theory with Einstein’s Theory of General Relativity with a drawing about light

The article by Stephon Alexander was originally published March 16, 2017 for Nautilus. My excerpts are from a getpocket.com selection,

LIGHT IN THE GARDEN: This drawing by the Oakes brothers, Irwin Gardens at the Getty in Winter, inspired the author to think anew about quantum mechanics and general relativity. The meticulous drawing, done on curved paper, allows viewers to reflect on the act of perception. Credit: Ryan and Trevor Oakes [downloaded from http://nautil.us/issue/46/balance/what-this-drawing-taught-me-about-four_dimensional-spacetime]

My aim as a theoretical physicist is to unite quantum theory with Einstein’s Theory of General Relativity. While there are a few proposals for this unification, such as string theory and loop quantum gravity, many roadblocks to a complete unification remain.

Einstein’s theory tells us the gravitational force is a direct manifestation of space and time bending. The sun bends the fabric of space, much like a sleeping person bends a mattress. Planetary orbits, including Earth’s, are motion along the contours of the bent space created by the sun. This theory provides some critical insights into the nature of light.

… one summer, I had the most unexpected breakthrough. Beth Jacobs, a member of the New York Academy of Sciences’ Board of Governors, invited me and some friends to her New York City apartment to meet the Oakes twins, artists who have gained attention in recent years for their drawings as well as the innovative technique and inventions they deploy to create them. An Oakes work, Irwin Gardens at the Getty in Winter (2011), an intricate drawing of the famous gardens designed by Robert Irwin at The Getty Museum in Los Angeles, was displayed on the balcony of Jacobs’ apartment overlooking Central Park, with the backdrop of the New York City skyline lit with a warm orange sky moments before sunset.

As I gazed at the drawing, I could feel the artists challenging me to reconsider the nature of light. I began to realize I should consider not only the physics of light, but also how light information is perceived by observers, when theorizing and conceiving new principles to unify quantum mechanics and general relativity. …

Ryan and Trevor Oakes, 35, have been exploring the impact and intersection of visual perception and the physics of light since they were kids. After attending The Cooper Union for the Advancement of Science and Art in New York City, and years of experimentation and inventing new techniques, the twins exploited the notion that light information is better described when originating from a spherical surface.

Fascinating stuff. BTW, you can find the original article here on Nautilus.

Quantum entanglement in near-macroscopic objects

Researchers at Finland’s Aalto University seem excited in an April 25, 2018 news item on phys.org,

Perhaps the strangest prediction of quantum theory is entanglement, a phenomenon whereby two distant objects become intertwined in a manner that defies both classical physics and a common-sense understanding of reality. In 1935, Albert Einstein expressed his concern over this concept, referring to it as “spooky action at a distance.”

Today, entanglement is considered a cornerstone of quantum mechanics, and it is the key resource for a host of potentially transformative quantum technologies. Entanglement is, however, extremely fragile, and it has previously been observed only in microscopic systems such as light or atoms, and recently in superconducting electric circuits.

In work recently published in Nature, a team led by Prof. Mika Sillanpää at Aalto University in Finland has shown that entanglement of massive objects can be generated and detected.

The researchers managed to bring the motions of two individual vibrating drumheads—fabricated from metallic aluminium on a silicon chip—into an entangled quantum state. The macroscopic objects in the experiment are truly massive compared to the atomic scale—the circular drumheads have a diametre similar to the width of a thin human hair.

An April 20,2018 Aalto University press release (also on EurekAlert), which originated the news item, provides more detail,

‘The vibrating bodies are made to interact via a superconducting microwave circuit. The electromagnetic fields in the circuit carry away any thermal disturbances, leaving behind only the quantum mechanical vibrations’, says Professor Sillanpää, describing the experimental setup.

Eliminating all forms of external noise is crucial for the experiments, which is why they have to be conducted at extremely low temperatures near absolute zero, at –273 °C. Remarkably, the experimental approach allows the unusual state of entanglement to persist for long periods of time, in this case up to half an hour. In comparison, measurements on elementary particles have witnessed entanglement to last only tiny fractions of a second.

‘These measurements are challenging but extremely fascinating. In the future, we will attempt to teleport the mechanical vibrations. In quantum teleportation, properties of physical bodies can be transmitted across arbitrary distances using the channel of “spooky action at a distance”. We are still pretty far from Star Trek, though,’ says Dr. Caspar Ockeloen-Korppi, the lead author on the work, who also performed the measurements.

The results demonstrate that it is now possible to have control over the most delicate properties of objects whose size approaches the scale of our daily lives. The achievement opens doors for new kinds of quantum technologies, where the entangled drumheads could be used as routers or sensors. The finding also enables new studies of fundamental physics in, for example, the poorly understood interplay of gravity and quantum mechanics.

The team also included scientists from the University of New South Wales in Australia, the University of Chicago in the USA, and the University of Jyväskylä in Finland, whose theoretical innovations paved the way for the laboratory experiment.

An illustration has been made available,

An illustration of the 15-micrometre-wide drumheads prepared on silicon chips used in the experiment. The drumheads vibrate at a high ultrasound frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Image: Aalto University / Petja Hyttinen & Olli Hanhirova, ARKH Architects.

Here’s a link to and a citation for the paper,

Stabilized entanglement of massive mechanical oscillators by C. F. Ockeloen-Korppi, E. Damskägg, J.-M. Pirkkalainen, M. Asjad, A. A. Clerk, F. Massel, M. J. Woolley & M. A. Sillanpää. Nature volume 556, pages478–482 (2018) doi:10.1038/s41586-018-0038-x Published online: 25 April 2018

This paper is behind a paywall.

Nanoparticles and strange forces

An April 10, 2017 news item on Nanowerk announces work from the University of New Mexico (UNM), Note: A link has been removed,

A new scientific paper published, in part, by a University of New Mexico physicist is shedding light on a strange force impacting particles at the smallest level of the material world.

The discovery, published in Physical Review Letters (“Lateral Casimir Force on a Rotating Particle near a Planar Surface”), was made by an international team of researchers lead by UNM Assistant Professor Alejandro Manjavacas in the Department of Physics & Astronomy. Collaborators on the project include Francisco Rodríguez-Fortuño (King’s College London, U.K.), F. Javier García de Abajo (The Institute of Photonic Sciences, Spain) and Anatoly Zayats (King’s College London, U.K.).

An April 7,2017 UNM news release by Aaron Hill, which originated the news item, expands on the theme,

The findings relate to an area of theoretical nanophotonics and quantum theory known as the Casimir Effect, a measurable force that exists between objects inside a vacuum caused by the fluctuations of electromagnetic waves. When studied using classical physics, the vacuum would not produce any force on the objects. However, when looked at using quantum field theory, the vacuum is filled with photons, creating a small but potentially significant force on the objects.

“These studies are important because we are developing nanotechnologies where we’re getting into distances and sizes that are so small that these types of forces can dominate everything else,” said Manjavacas. “We know these Casimir forces exist, so, what we’re trying to do is figure out the overall impact they have very small particles.”

Manjavacas’ research expands on the Casimir effect by developing an analytical expression for the lateral Casimir force experienced by nanoparticles rotating near a flat surface.

Imagine a tiny sphere (nanoparticle) rotating over a surface. While the sphere slows down due to photons colliding with it, that rotation also causes the sphere to move in a lateral direction. In our physical world, friction between the sphere and the surface would be needed to achieve lateral movement. However, the nano-world does not follow the same set of rules, eliminating the need for contact between the sphere and the surface for movement to occur.

“The nanoparticle experiences a lateral force as if it were in contact with the surface, even though is actually separated from it,” said Manjavacas. “It’s a strange reaction but one that may prove to have significant impact for engineers.”

While the discovery may seem somewhat obscure, it is also extremely useful for researchers working in the always evolving nanotechnology industry. As part of their work, Manjavacas says they’ve also learned the direction of the force can be controlled by changing the distance between the particle and surface, an understanding that may help nanotech engineers develop better nanoscale objects for healthcare, computing or a variety of other areas.

For Manjavacas, the project and this latest publication are just another step forward in his research into these Casimir forces, which he has been studying throughout his scientific career. After receiving his Ph.D. from Complutense University of Madrid (UCM) in 2013, Manjavacas worked as a postdoctoral research fellow at Rice University before coming to UNM in 2015.

Currently, Manjavacas heads UNM’s Theoretical Nanophotonics research group, collaborating with scientists around the world and locally in New Mexico. In fact, Manjavacas credits Los Alamos National Laboratory Researcher Diego Dalvit, a leading expert on Casimir forces, for helping much of his work progress.

“If I had to name the person who knows the most about Casimir forces, I’d say it was him,” said Manjavacas. “He published a book that’s considered one of the big references on the topic. So, having him nearby and being able to collaborate with other UNM faculty is a big advantage for our research.”

Here’s a link to and a citation for the paper,

Lateral Casimir Force on a Rotating Particle near a Planar Surface by Alejandro Manjavacas, Francisco J. Rodríguez-Fortuño, F. Javier García de Abajo, and Anatoly V. Zayats. Phys. Rev. Lett. (Vol. 118, Iss. 13 — 31 March 2017) 118, 133605 DOI:https://doi.org/10.1103/PhysRevLett.118.133605 Published 31 March 2017

This paper is behind a paywall.

Why are jokes funny? There may be a quantum explanation

Some years ago a friend who’d attended a conference on humour told me I really shouldn’t talk about humour until I had a degree on the topic. I decided the best way to deal with that piece of advice was to avoid all mention of any theories about humour to that friend. I’m happy to say the strategy has worked well although this latest research may allow me to broach the topic once again. From a March 17, 2017 Frontiers (publishing) news release on EurekAlert (Note: A link has been removed),

Why was 6 afraid of 7? Because 789. Whether this pun makes you giggle or groan in pain, your reaction is a consequence of the ambiguity of the joke. Thus far, models have not been able to fully account for the complexity of humor or exactly why we find puns and jokes funny, but a research article recently published in Frontiers in Physics suggests a novel approach: quantum theory.

By the way, it took me forever to get the joke. I always blame these things on the fact that I learned French before English (although my English is now my strongest language). So, for anyone who may immediately grasp the pun: Why was 6 afraid of 7? Because 78 (ate) 9.

This news release was posted by Anna Sigurdsson on March 22, 2017 on the Frontiers blog,

Aiming to answer the question of what kind of formal theory is needed to model the cognitive representation of a joke, researchers suggest that a quantum theory approach might be a contender. In their paper, they outline a quantum inspired model of humor, hoping that this new approach may succeed at a more nuanced modeling of the cognition of humor than previous attempts and lead to the development of a full-fledged, formal quantum theory model of humor. This initial model was tested in a study where participants rated the funniness of verbal puns, as well as the funniness of variants of these jokes (e.g. the punchline on its own, the set-up on its own). The results indicate that apart from the delivery of information, something else is happening on a cognitive level that makes the joke as a whole funny whereas its deconstructed components are not, and which makes a quantum approach appropriate to study this phenomenon.

For decades, researchers from a range of different fields have tried to explain the phenomenon of humor and what happens on a cognitive level in the moment when we “get the joke”. Even within the field of psychology, the topic of humor has been studied using many different approaches, and although the last two decades have seen an upswing of the application of quantum models to the study of psychological phenomena, this is the first time that a quantum theory approach has been suggested as a way to better understand the complexity of humor.

Previous computational models of humor have suggested that the funny element of a joke may be explained by a word’s ability to hold two different meanings (bisociation), and the existence of multiple, but incompatible, ways of interpreting a statement or situation (incongruity). During the build-up of the joke, we interpret the situation one way, and once the punch line comes, there is a shift in our understanding of the situation, which gives it a new meaning and creates the comical effect.

However, the authors argue that it is not the shift of meaning, but rather our ability to perceive both meanings simultaneously, that makes a pun funny. This is where a quantum approach might be able to account for the complexity of humor in a way that earlier models cannot. “Quantum formalisms are highly useful for describing cognitive states that entail this form of ambiguity,” says Dr. Liane Gabora from the University of British Columbia, corresponding author of the paper. “Funniness is not a pre-existing ‘element of reality’ that can be measured; it emerges from an interaction between the underlying nature of the joke, the cognitive state of the listener, and other social and environmental factors. This makes the quantum formalism an excellent candidate for modeling humor,” says Dr. Liane Gabora.

Although much work and testing remains before the completion of a formal quantum theory model of humor to explain the cognitive aspects of reacting to a pun, these first findings provide an exciting first step and opens for the possibility of a more nuanced modeling of humor. “The cognitive process of “getting” a joke is a difficult process to model, and we consider the work in this paper to be an early first step toward an eventually more comprehensive theory of humor that includes predictive models. We believe that the approach promises an exciting step toward a formal theory of humor, and that future research will build upon this modest beginning,” concludes Dr. Liane Gabora.

Here’s a link to and a citation for the paper,

Toward a Quantum Theory of Humor by Liane Gabora and Kirsty Kitto. Front. Phys., 26 January 2017 | https://doi.org/10.3389/fphy.2016.00053

This paper has been published in an open access journal. In viewing the acknowledgements at the end of the paper I found what I found to be a surprising funding agency,

This work was supported by a grant (62R06523) from the Natural Sciences and Engineering Research Council of Canada. We are grateful to Samantha Thomson who assisted with the development of the questionnaire and the collection of the data for the study reported here.

While I’m at this, I might as well mention that Kirsty Katto is from the Queensland University of Technology (QUT) in Australia and, for those unfamiliar with the geography, the University of British Columbia is the the Canada’s province of British Columbia.

Quantum and classical physics may be closer than we thought

It seems that a key theory about the boundary between the quantum world and our own macro world has been disproved and I think the July 21, 2015 news item on Nanotechnology Now says it better,

Quantum theory is one of the great achievements of 20th century science, yet physicists have struggled to find a clear boundary between our everyday world and what Albert Einstein called the “spooky” features of the quantum world, including cats that could be both alive and dead, and photons that can communicate with each other across space instantaneously.

For the past 60 years, the best guide to that boundary has been a theorem called Bell’s Inequality, but now a new paper shows that Bell’s Inequality is not the guidepost it was believed to be, which means that as the world of quantum computing brings quantum strangeness closer to our daily lives, we understand the frontiers of that world less well than scientists have thought.

In the new paper, published in the July 20 [2015] edition of Optica, University of Rochester [New York state, US] researchers show that a classical beam of light that would be expected to obey Bell’s Inequality can fail this test in the lab, if the beam is properly prepared to have a particular feature: entanglement.

A July 21, 2015 University of Rochester news release, which originated the news item, reveals more about the boundary and the research,

Not only does Bell’s test not serve to define the boundary, the new findings don’t push the boundary deeper into the quantum realm but do just the opposite. They show that some features of the real world must share a key ingredient of the quantum domain. This key ingredient is called entanglement, exactly the feature of quantum physics that Einstein labeled as spooky. According to Joseph Eberly, professor of physics and one of the paper’s authors, it now appears that Bell’s test only distinguishes those systems that are entangled from those that are not. It does not distinguish whether they are “classical” or quantum. In the forthcoming paper the Rochester researchers explain how entanglement can be found in something as ordinary as a beam of light.

Eberly explained that “it takes two to tangle.” For example, think about two hands clapping regularly. What you can be sure of is that when the right hand is moving to the right, the left hand is moving to the left, and vice versa. But if you were asked to guess without listening or looking whether at some moment the right hand was moving to the right, or maybe to the left, you wouldn’t know. But you would still know that whatever the right hand was doing at that time, the left hand would be doing the opposite. The ability to know for sure about a common property without knowing anything for sure about an individual property is the essence of perfect entanglement.

Eberly added that many think of entanglement as a quantum feature because “Schrodinger coined the term ‘entanglement’ to refer to his famous cat scenario.” But their experiment shows that some features of the “real” world must share a key ingredient of Schrodinger’s Cat domain: entanglement.

The existence of classical entanglement was pointed out in 1980, but Eberly explained that it didn’t seem a very interesting concept, so it wasn’t fully explored. As opposed to quantum entanglement, classical entanglement happens within one system. The effect is all local: there is no action at a distance, none of the “spookiness.”

With this result, Eberly and his colleagues have shown experimentally “that the border is not where it’s usually thought to be, and moreover that Bell’s Inequalities should no longer be used to define the boundary.”

Here’s a link to and a citation for the paper,

Shifting the quantum-classical boundary: theory and experiment for statistically classical optical fields by Xiao-Feng Qian, Bethany Little, John C. Howell, and J. H. Eberly. Optica Vol. 2, Issue 7, pp. 611-615 (2015) •doi: 10.1364/OPTICA.2.000611

This paper is open access.