Tag Archives: quantum theory

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.