Assistant Professor

PhD position in the theory of quantum networks

Many theoretical challenges need to be solved in order to implement the first quantum networks. In this PhD position, you will have the opportunity to solve some of these practical challenges. You will join the theory group of David Elkouss in QuTech at TU Delft and will work in close collaboration with the experimental groups of Ronald Hanson and Tim Taminiau and with the theory group of Stephanie Wehner.

You have a master’s degree and an exceptional track record in either maths, physics, computer science or electrical engineering. You have demonstrated your abilities in at least one research project. A background in quantum information and/or programming are a plus.

The deadline is May the 1st but applications will be considered until the position is filled.

To apply please email the following documents in pdf format to d(dot)elkousscoronas(at)tudelft(dot)nl:

  • CV
  • Your complete transcript
  • Letter of motivation
  • 2 letters of reference from faculty who have supervised you in a project. These should be emailed directly to d(dot)elkousscoronas(at)tudelft(dot)nl and have the subject “Reference for [YourName]”.
  • One report from a project that you have done.

Gamifying Quantum Theory

Over the past few years, the trend of gamification has gradually seeped into quantum research, education and outreach, so that we now have a critical mass of games based on quantum mechanics. I thought the time was right to discuss quantum gamification at the APS March meeting, so I have organized a session on Thursday at 2:30pm on Gamification and other Novel Approaches in Quantum Physics Outreach. If you need a break from superconducting qubits (and I know you do), why not go and learn about this exciting new area.

Also, while you are sitting through a typical March meeting talk where the speaker tries to give their usual 30min talk in 10min, rushing through a series of incomprehensible slides, or when you have gone back to the hotel early with a Subway sandwich having lost all your friends and colleagues in the morass of physicists, why not distract yourself by giving some quantum games a try? Here are some possibilities:

Games to be discussed at the March Meeting:

Other Quantum Games

In the rest of this article, I briefly review my top picks for quantum games, bearing in mind that I haven’t played all of them. In particular, since I did not have a 12 year old handy, I have not tried any of the Minecraft mods. Also, Quantum Chess is still in private beta, but you can see an interesting talk on it by its creator Chris Cantwell here, and you can watch Stephen Hawking play Quantum Chess with Paul Rudd (Ant Man) here. Following the style of gaming magazines, I will give each of my picks a seemingly arbitrary score out of 10 for their science, their gameplay, and their sound and graphics.

Quantum games broadly fit into four overlapping categories, and I will review my top pick for each one. The categories are:
Crowdsourcing Research: These games aim to use the data generated by humans playing the game to solve research problems in quantum physics. This is the same idea as the well-known FoldIt game, which uses humans to solve protein folding problems.
Building Intuition: The idea of these games is to build intuition for how quantum mechanics works by having a game that is built on the rules of an actual quantum mechanical system, without any equations. The aim is not exactly education, but rather to make the abstract features of quantum theory seem more concrete.
Education: The aim of these games is to actually teach some quantum mechanics. If a student plays through one of these games, then they ought to be better equipped for their modern physics and quantum mechanics classes. These games might also be used as a supplement in such classes.
Outreach: The aim of these games is to get people excited about quantum mechanics by putting some quantum ideas in front of people who might not otherwise see them. If they are educational, then it is only at the popular science level.
Top Pick for Crowdsourcing Research: Quantum Moves
Platform: Windows, Linux, Mac, Android, iOS (basically everything)
Project Lead: Jacob Sherson (Aarhus University)
Science: 9
Gameplay: 6
Graphics and sound: 9
The Science:

The aim of Quantum Moves is to help figure out how to move single atoms/ions around in an ion trap using lasers without changing their quantum state. Computer algorithms exist to optimize this, but apparently better results can be obtained by running human-generated solutions through an optimization algorithm.

This game gets top marks for science because it is the only game I am aware of to have resulted in a Nature Publication. The human generated data has been used to build an efficient heuristic optimization algorithm that outperforms other numerical methods. In fact the Science@Home team behind this game have several publications and preprints based on Quantum Moves, they have several other games in development. The most interesting of these Quantum Minds, which is being used by cognitive scientists to study how humans come up with solutions in games like Quantum Moves.

The Game:

The game itself is quite simple. You are presented with a one dimensional curve, which represents the potential of some physical system. Located somewhere along this curve, usually in a potential dip, will be a “liquid” that has funny properties when you move it around. The “liquid” represents the wavefunction of a single atom. You have a cursor, which you can drag around the screen to move another potential dip, which represents the effect of a laser. The aim is to move the “liquid” to a target area while keeping its shape the same as much as possible, i.e. move the atom while keeping the fidelity with (a translated version of) the initial state as high as possible.
The “liquid” has some very counter-intuitive properties that are unlike anything most players will have encountered. Well, it is, after all, a wavefunction and not a liquid, but “liquid” is the terminology used in the game. If you are a quantum physicist, then you will know a few tricks that will help you through the initial levels. For example, by the adiabatic theorem, you know that moving an isolated potential dip with an atom in it very slowly is probably a good idea, and you know that when you want to transfer an atom from one dip to another similarly shaped one then you know that making a symmetric double-well will be good for tunneling. Other than that, the behavior of the “liquid” is, to me at least, extremely unintuitive. It sloshes around unpredictably and it is very difficult to figure out what will work well. A few hints are given on the website, e.g. it turns out that shaking the well from side to side a little as you move it helps to maintain the shape of the wavefunction.
The unintuitive behavior of the “liquid” makes for a steep learning curve, and makes the game not especially fun to play, which is why I have only given it 6 for gameplay. Puzzle games can be placed on a spectrum from concrete to abstract. A concrete puzzle game makes use of things that players already have strong correct intuitions for, and the challenge is just to combine these elements in a clever way. An example of a concrete puzzle game is Lemmings, which uses intuitions like, “if a lemming falls a long way it will splat on the ground and die”. In contrast, an abstract puzzle game makes use of elements and rules that seem completely arbitrary when you first encounter them. You have to learn what the rules even mean and build intuition for them as you go. Quantum Moves, and indeed most quantum puzzlers, are on the extreme abstract end of the spectrum.
An abstract puzzler can be fun to play, but I think that most players would want considerable help in the early levels as an aid to building intuition. It is not too hard to get high scoring solutions on the first couple of levels, but I quickly struggled to get good scores thereafter. My inability to figure out how to improve my scores turned me off the game fairly rapidly. From a science point of view, you obviously want to present the player with hard problems that we do not know how to solve easily, but if you are trying to compete for distracted players with other more fun games then you are quickly going to lose players to other games like Angry Birds. Players who are more persistent or more fond of arbitrary abstract thinking then I am may enjoy this game more than I did.
The graphics and visuals of this game are very good, comparable to professionally produced games that you might play on your smartphone.
Top Pick for Building Intuition: Decodoku
Platform: Windows, Mac, Web, Android, iOS
Project Lead: James Wootton (University of Basel)
Science: 9
Gameplay: 8
Graphics and sound: 5

The Science:

There is a large overlap between my game categories, and Decodoku is also a crowdsourcing research game, but its style of gameplay is similar to other building intuition games like MeQanic, and it is more fun than the others I have played, so I decided to put it here. I have not read a technical account of the science behind Decodoku, but from what I can gather it is about correcting errors in a surface code, intended to be used in topological quantum computing.
You are presented with a grid, representing qubits on a torus. From time to time, a syndrome measurement is made and you have to correct the errors. Now, we know how to correct errors in a quantum error correction code, but the idea is to optimize the order in which multiple errors are corrected so that the logical qubits will survive as long as possible. In a toroidal code that means that you do not want an error syndrome that stretches from one end of the grid to the other. The data from this game will be used to optimize the order of error correction in actual algorithms in some way, but, as I said, I have not seen a technical discussion of this yet.
The Game:

The game is a puzzle game involving combining numbers, in some ways similar to the viral hit 2048. From time to time, numbers in different colors will appear on a grid. You can combine to numbers of the same color that are next to each other and they will add together forming a single number. When they reach a multiple of ten they disappear. The objective is to keep going for as long as possible until you get a string of numbers that goes from one edge of the grid to another.
If you were a 2048 addict, you will probably find this game only marginally less addictive (the lack of sliding blocks is slightly less satisfying). You really do not need to know the quantum mechanics behind the puzzle, and, unlike in Quantum Moves, I doubt it will help you. You just need to know how numbers add to multiples of ten. I can see myself playing this game in the same sorts of situations I played 2048, i.e. when I have five or ten minutes of waiting time so it is not worth starting something that would take a long time. I feel a bit better about playing Decodoku than 2048, knowing that it could actually contribute to science in some way.
The graphics look like they were programmed on a Commodore 64 in the 1980’s. I assume that is because James is not a professional game developer rather than being deliberately retro, but in any case, graphics are not a major factor in the playability of this kind of game.
Top Pick for Education: Quantum Game with Photons
Platform: Web
Project Lead: Piotr Migdal (Freelance)
Science: 8
Gameplay: 8
Graphics and sound: 8

The Science:

This game is about linear optics, and it basically explores what you can do with photons on an optical table. You can place objects like beamsplitters, mirrors, etc. on a grid, then fire the lasers and see which detectors fire.
The idea of this is to allow people to play around with quantum optics freestyle, as well as solving puzzles. Most of the puzzles involve single-photon interference, although there is some entanglement on later levels.
I think that introducing quantum theory via photon interferometry is a great idea, as it allows you to get to the mathematics of a qubit quickly for students who have studied some classical optics. I can see myself using this game in sandbox mode as a demonstration tool in the classroom, as well as having the students solve some of the puzzles.
The Game:

You can play the game in a sandbox mode, or solve a series of puzzles where certain elements are fixed and you have to place a limited number of other elements to get certain detectors to click. Many of these puzzles are based on well-known experiments like the Mach-Zehnder interferometer or the Elitzur-Vaidman bomb. However, some of them are challenging even for a physicist experienced in the theory of weird and wonderful interferometers, e.g. they involve putting beamsplitters in unusual places that you would not immediately think of. The learning curve is well-judged and the game is fun to play, at least if you are someone who already likes to think about physics. I don’t know how well it would do as a tool for drawing people into physics.

This game is browser based and the web design is very slick and pretty. The game board itself is just a minimalist white grid, with symbols for the various elements. It could be prettier, but it is perfectly functional.

 

Top Pick for Outreach: The BIG Bell Test
Platform: Web
Project Lead: Morgan Mitchell (ICFO, Barcelona)
Science: 8
Gameplay: 7
Graphics and sound: 10
The Science:

On November 30, 2016, several labs around the world participated in the BIG Bell Test, which aimed to close the free will loophole in Bell’s theorem by using randomness generated by human “free will” to choose the measurement settings. Now, if you believe that human choice is genuinely free, and uncorrelated with anything else in the universe, then this really does close a relatively minor loophole in Bell’s theorem. On the other hand, there is reason to doubt that genuine free will exists, and there are also other ways of getting the same sort of loophole, such as retrocausality (the future affects the past) that this experiment does not address.

However, the BIG Bell Test was great for outreach, as the website, games, and videos were very slickly done and it did genuinely make you feel like you were contributing to science in a fun and simple way. It probably introduced Bell’s theorem to many people who would not have known about it otherwise.

The Game:

You can still play the BIG Bell Test games online, although there is little point as the experiments are now over. The basic idea is to get participants to mash on the 0 and 1 keys in order to extract random numbers to be used in the experiments. On the face of it, this task would be pretty boring, and we know that humans are not very good at generating random sequences anyway, so the game has to address these two issues.

To address the boredom issue, the generation process is divided into a number of short subgames that have different themes. For example, in the first game your randomness propels you forward along a road in a village, and you have to collect atoms along the way. In the second game, an oracle attempts to predict which key you will press next, and your objective is to outsmart the oracle by being unpredictable.

To address the randomness issue, some statistical tests are run in the background. The player is given feedback on how well they are doing, and is encouraged to be “more random” if necessary. You are scored on each game based on how random you are, and there is a target level of randomness to achieve in each game. I am not sure how all this works on the mathematical level. I presume the game is not computing Kolmogorov complexity, as this is uncomputable in general, but rather some simpler statistical tests that have been found to work well in practice. I also assume that randomness extraction is run on the resulting data. In any case, on November 30, at the end of the game you were told how many bits of randomness you generated, and in which lab they were used, which is a nice touch.

One of the most compelling aspects of the game is the visuals, which are done in a monochrome style that looks hand-drawn and cartoon-like. This really helps to draw the player in, as you want to see what graphics are coming up in the next game. The only complaint I have is that the 0’s and 1’s that you generate are represented by halves of a yin-yang symbol. To put it bluntly, to me, these look like sperm. For me, this just added to the quirky charm of the graphics, but I imagine it might be distracting for some players.

GQI Elections

This year the Topical Group on Quantum Information (GQI) is holding elections for the following executive committee positions of Vice Chair and Member at Large.

Vice Chair Candidates: Jay Gambetta and Susan Coppersmith

Member at Large Candidates: Stephanie Wehner and Ryan Babbush

Listed below is a  statement from each candidate.

Jay Gambetta (Candidate for Vice Chair)

Quantum information science is the area of science that blurs standard boundaries and pushes us to understand nature at its most fundamental level. It brings together scientists from virtually all scientific disciplines to collectively try and understand the depths of fundamental physics and information theory for explaining aspects of the natural world around us. We research fundamental questions related to how physics and information theory are intertwined, to how nature computes, and to the foundations of the world around us. One would be hard-pressed to find any other division in the APS that covers such a broad and rich area, and I am very excited to run for Vice Chair of the executive committee of the Topical Group of Quantum Information (GQI).

Quantum, as ubiquitous in popular science as the word has become, is a pre-eminent pillar of physics and the beauty of quantum information science is its diverse and powerful nature. On one day a researcher could be working on foundations of physics and on the following day be considering applications of a new model of computation. The breadth of our research field is one of the many reasons why we are on the path to becoming a division of the APS. The evolution and growth of our field of quantum information has accelerated in recent years, as is clearly evident when I look back at my own personal journey starting from foundational research on open quantum systems to working closely with experimentalists on demonstrating concepts of quantum information processing.

It is a very exciting time for our community as we have recently met the requirements for becoming a division of the APS and last year, thanks to the generous support of IBM, we have our own award – Rolf Landauer and Charles H. Bennett Award in Quantum Computing– which recognizes the great work of our community. My goals for the GQI are 1) to continue the excellent work of the executive committee before me and to make sure we remain a division through increasing membership, 2) to encourage and develop more recognition for the younger researchers in quantum information – we need more awards and diversity for them, and 3) to increase the visibility of quantum information science in the public sphere. This is an area that is very important to me personally as in recent years I have been deeply involved in creating the IBM Quantum Experience, which is a substantial collaborative effort with colleagues that provides free public access to a fully-functioning small quantum computer. We have over 30K users learning about quantum information science as well as a large number of researchers using the Experience as a world class research tool to help produce research papers and further our understanding of nature.

In the past, I have served the GQI by chairing for the last two years the APS Fellowship committee where we have been very successful and had 11 top researchers accepted as GQI-sponsored APS fellows. As a topical group, we don’t have a final say in the selection of our Fellows since they are voted on by the governing division. To have such a large number be accepted for APS fellowship points to the top-class research being performed and the subsequent recognition of our researchers by the broader physics community.

Susan Coppersmith (Candidate for Vice Chair)

It is a tremendously exciting time for the field of quantum information. The APS Topical Group on Quantum Information (GQI) is important for the field not only for its role in facilitating communication between quantum information researchers, but also because of its role in communicating the great intellectual challenges and achievements of the field to other physicists as well as the general public.

I am honored to be a candidate to serve GQI as Vice-Chair. If elected, I will strive to make the organization as fair and efficient as possible, I will work to increase the diversity of the membership to maintain a membership sufficient for Division status, and I will also work hard to enhance the appreciation of quantum information in the broader community of physicists and in society at large.

Dr. Susan Coppersmith is a theoretical physicist who has been working in the field of quantum information science since 2001. She is currently a Professor of Physics at the University of Wisconsin-Madison. Her Ph.D. in physics is from Cornell University, and she has been a postdoc at Brookhaven National Laboratory and at AT&T Bell Laboratories, a visiting lecturer at Princeton University, a member of technical staff at AT&T Bell Laboratories, and a professor at the University of Chicago. She has been working to develop qubits using quantum dots in silicon/silicon-germanium heterostructures, and has also investigated the properties of algorithms involving single- and multi-particle quantum random walks.

Dr. Coppersmith has served as Chair of the UW-Madison physics department, as a member of the NORDITA advisory board, as a member of the Mathematical and Physical Science Advisory Committee of the National Science Foundation, and as a Trustee at the Aspen Center for Physics. She has served as Chair of the Division of Condensed Matter Physics and of the Group for Statistical and Nonlinear Physics of the American Physical Society, as Chair of the Division on Physics of the American Association for the Advancement of Science, as Chair of the Board of Trustees of the Gordon Research Conferences, and as Chair of the External Advisory Board of the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara. She is a fellow of the American Physical Society, the American Association for the Advancement of Science, and the American Academy of Arts and Sciences, and has been elected to membership in the National Academy of Sciences.

Stephanie Wehner (Candidate for Member at Large)

I have never been as excited about quantum information as in the past three years. On the one hand, quantum information is proving its worth to understand fundamental aspects of nature; the term “it from bit” capturing the idea, or maybe rather the dream, that all of nature could be deciphered using the perspective of information processing.

On the other hand, we are at last edging close to seeing quantum computing technologies being realized by most impressive experimental efforts. Recent years have seen a paradigm shift in the field, marked by the commitment of several large companies such as Intel, Microsoft, and Google as well as international efforts such as the EU Flagship on quantum technologies.

I believe quantum information has always drawn great strength from interdisciplinary collaboration. It is now time to fulfill the promise of quantum computing and communication technologies – if possible. However, without joint efforts from both theoretical and experimental physics, computer science, and mathematics we cannot succeed. The recent paradigm shift also sees a necessary expansion into the domain of engineering, and I believe we will see a new field of applied quantum computer science emerge which in analogy to most of classical computer science employs a heuristic approach to realize and utilize quantum technologies.

GQI now has the potential to bring the old and new communities in quantum information together. I will contribute to GQI stepping up to a Division in order to realize this goal. Recent developments also highlight new career opportunities for junior researchers to enter or indeed found quantum industry. I would like GQI to help facilitate such opportunities and navigate challenges.

I am honored to be a candidate for the GQI member-at-large. Due to my own interdisciplinary background, my collaborations across disciplines with both theory and experiment, as well as my international experience in the US, Asia and Europe I believe I am well positioned to represent the diverse GQI community. I enjoyed making a difference by founding QCRYPT and advancing QuTech Academy, and I would now be excited to serve in the APS to take GQI forward.

Stephanie Wehner is an Antoni van Leeuwenhoek Professor at QuTech, Delft University of Technology in the Netherlands. She received her PhD degree in computer science from the University of Amsterdam in 2008, followed by two years as a Postdoctoral Scholar at the California Institute of Technology. From 2010-2014 she was an Assistant Professor and later Dean’s Chair Associate Professor at the Centre for Quantum Technologies, National University of Singapore. Prior to her academic career, Stephanie has worked for a few years in the network security industry as a professional hacker.

Stephanie’s passion is the theory of quantum information in all its facets, and she has published more than 60 articles on a wide range of topics in physics and computer science, ranging from more applied subjects such as (quantum) information theory and quantum cryptography to fundamental questions in quantum foundations and quantum thermodynamics. Some of her contributions to scientific progress have been selected for Science’s “Top 10 Breakthroughs of 2015”, and Nature’s “Science Events that shaped 2015”, and received the Paul Ehrenfest Award for Quantum Foundations. Stephanie was awarded personal grants including the ERC Starting Grant.

Stephanie is one of the founders of QCRYPT, which has grown to be the largest international conference in quantum cryptography. She has served on the steering committees of several conferences, QCRYPT 2011-2016, QIP 2014-2016, and QCMC 2015-2017, as well as on the editorial board of the New Journal of Physics. She has organized several international conferences such as QCRYPT, QIP and workshops such as the IMS workshop on Quantum Thermodynamics. At QuTech, she is part of the management team, as well as responsible for QuTech Academy, an interdisciplinary education program in quantum technologies for students in engineering, physics, computer science and mathematics. She enjoys spreading the word about quantum information, for example by teaching online in edX QuCryptoX, and contributing to outreach by speaking at events such as TEDx and New Scientist Live.

Ryan Babbush (Candidate for Member at Large)

Five years ago, a wise postdoc sat me down for a serious conversation; they urged me to abandon quantum information while I still could because there were no jobs and the field seemed doomed. Fortunately, we both ignored that advice and today, laugh about that discussion. The size and number of industrial quantum groups is growing, funding for academic researchers and government programs is increasing, as is the size and quality of quantum hardware. Now is an extremely exciting time for the field.

However, now is also an uncertain time for the future of science in the United States. Michael Lubell, director of public affairs for the APS, told Nature that “Trump will be the first anti-science president we have ever had. The consequences are going to be very, very severe”. Whether one agrees with this sentiment or not, with both executive and legislative branches under Republican control, the incoming administration will have tremendous power to reshape science policy in America. How policy changes will affect quantum research is unclear and quite possibly, still undecided by lawmakers. In my view, how the APS will represent our interests to these lawmakers in 2017 is the most important issue in the current APS election.

If I am elected Member-at-Large of GQI, I will use my position on the GQI committee to advocate for increased lobbying on behalf of our group’s interests. As a representative of the APS and an American citizen, I will participate in all APS lobbying efforts and personally travel to DC to meet with congressional staffers about the importance of supporting quantum research. I will wear a tie and tell anyone willing to listen that academic and government research in quantum information is essential for the development of future technology and also creates industry jobs (such as mine). I will tell them that America’s competitive advantage in this field demands the availability of visas for the best physicists to work here, regardless of their nationality. But most importantly, I will tell them about the promise of quantum information and remind them that leadership in science is part of what makes America great.

Ryan Babbush is a Research Scientist in the Quantum AI Lab at Google where he works closely with experimentalists to design quantum algorithms for prototype quantum hardware. He has broad interests in quantum algorithms, quantum complexity, machine learning, superconducting qubits, chemical physics and electronic structure theory.

Ryan entered undergraduate studies intending to become a chemist. However, after two years of research in experimental chemistry and two trips to the hospital for toxic exposure in the laboratory, Ryan decided it was safer to be a theorist. As he quickly learned, most chemistry is just physics that’s too hard for physicists… unless the physicist has a quantum computer, in which case most chemistry is just a problem in the quantum complexity class BQP. This realization convinced Ryan to enter the field of quantum information. He graduated from Carleton College with a double major in Physics and Chemistry (2011) and headed to Harvard University where he joined the Aspuru-Guzik group, known for working at the intersection of quantum information and quantum chemistry. Ryan received both his masters in Physics (2013) and his PhD in Chemical Physics (2015) from Harvard University.

At Harvard and Google Ryan worked on developing efficient analog and digital protocols for quantum computing problems in chemistry and machine learning. He has collaborated with experimental groups using ion traps, NV centers, and several types of superconducting qubits to realize these algorithms. During his PhD he did internships with quantum groups at both Google and Microsoft. Upon disserting in 2015, he joined Google’s team as a permanent researcher.

Review of “Quantum Chance” by Nicolas Gisin

“Quantum Chance” (Springer, 2014) by Nicolas Gisin is a slim volume about entanglement, quantum nonlocality, and the Bell experiment.  (The book was originally published in French in 2012; this review is of the English translation.)  Gisin is well known both for his deep interest in the foundations of quantum mechanics and for his experimental expertise.  That expertise has made him a pioneer in the practical development of quantum cryptography; but, combined with his insight into quantum theory, it has also allowed him to devise ingenious tests of quantum mechanical predictions.  His long consideration of these questions informs every page of this book, where he presents his arguments in a clear and engaging style.

The book begins by postulating a peculiar telephone.  Alice and Bob–the heroes of many a paper on quantum information–each have a telephone, which is useless for communication:  it produces only random noise.  But they discover that the noise produced on the two sides is perfectly synchronized.  Being good scientists, they try to determine whether the correlations arise due to communication from one side to the other, or due to some common cause, such as a long random sequence stored identically in each telephone before they were distributed.

From this science fictional scenario we are led to the idea of a Bell experiment:  two widely separated experimenters, each equipped with a black box that has two settings and two possible outputs.  Gisin lays out the description of a Bell game (actually, the CHSH game), and derives the CHSH inequality that must be satisfied if the two black boxes cannot communicate, but are correlated due to a common cause.  He then describes how such a Bell test can be carried out in an actual quantum experiment, and how quantum mechanics predicts that the inequality is violated.  This, in the language commonly used in quantum theory, is quantum nonlocality.

From there he presents related concepts from the heart of quantum information:  the no-cloning theorem and entanglement. He describes how real world experiments have been designed to test Bell’s theorem, and how all tests to date have supported the predictions of quantum mechanics.  He discusses the two major loopholes in experimental Bell tests, the locality and detection loopholes.  (This book was written before the three loophole-free Bell experiments done in 2015.  Perhaps he will add them to a future edition, since Gisin himself is a major contributor to the study of such loopholes.)  He describes his 2008 experiment, which showed that any hidden superluminal communication between the two sides must be many times faster than the speed of light.

There are, of course, philosophical loopholes that are probably impossible to close, such as superdeterminism:  the idea that all of Alice and Bob’s choices, as well as the seemingly random outcomes are determined from the beginning of the universe.  Gisin briefly discusses a number of related topics, like the Free Will Theorem of Conway and Kochen, and outlines his more recent result (with collaborators Bancal et al.) that proves a remarkable extension of Bell’s theorem.  Using 3- and 4-body correlations, they show that if correlations arise from influences propagating at any finite velocity, they must eventually either disagree with the predictions of quantum mechanics or allow superluminal communication (or both).

In addition to its central focus on Bell experiments and nonlocality, the book also discusses some applications of entanglement.  There are two fairly brief chapters, one on random number generators and quantum cryptography and one on quantum teleportation, which hint at the large effort now being devoted to quantum-based technology.

The philosophical heart of the book, to which the author repeatedly returns, is this:  if quantum mechanics violates Bell inequalities, then the randomness of quantum measurements is not due to ignorance, like the seeming randomness of a tossed coin or of thrown dice.  Rather, it must be true randomness:  new information that spontaneously appears out of nowhere.  Gisin argues that because of its nonlocality, quantum mechanics is inconsistent with a deterministic, Newtonian world view.  This argument–like all arguments in quantum foundations–has been disputed, but I have never seen it presented with such cogency as in this book.

While “Quantum Chance” does not assume knowledge of quantum mechanics, and derives all its arguments from first principles, it will not be an easy read for most laypeople.  Several early chapters bristle with equations and tables, and the book draws on some math (like binary arithmetic and probability theory) that might be daunting to a mathematically unsophisticated reader.  However, it is easily readable by technical readers who are not specialists in quantum theory.  They will find it a concise and highly accessible introduction to Bell’s theorem, and to the ideas of entanglement and quantum nonlocality.  And specialists will find it interesting as well, as clearly presenting the ideas of one of our deep thinkers about quantum theory.

Q+ Hangout: David Perez-Garcia

Next Q+ Hangout is on the 12th of April!

As usual, if you are watching with a group and want to reserve a seat in the hangout then leave a comment on the event page:

https://plus.google.com/events/cbf9m2hsuf9kgvv3p61alo7h7lc

We also encourage individuals interested in active participation—which typically involves asking questions after the talk—to join the hangout. Otherwise you can watch on the livestream. Details follow.

Title: Size-driven quantum phase transitions

Speaker: David Perez-Garcia, Universidad Complutense de Madrid

Abstract: Most of the theoretical knowledge about quantum many body systems comes from performing numerical simulations. One tries to capture the relevant physical features of a system by extrapolating to the large system size the knowledge obtained in the analysis of an increasing sequence of finite-size systems, which must be small enough for the computer to be capable of giving an answer in a reasonable amount of time. In this work we show simple examples that totally defeat any such approach. More concretely, we construct translationally invariant quantum spin models on the 2D square lattice with reasonably small local dimension exhibiting the following surprising feature that we refer to as a “size-driven phase transition”‘: For all system sizes smaller than a threshold value L, the system has a unique ground state with product structure and a constant spectral gap to the first excited state, which also has product structure. However, for all system sizes larger than L, the system has topological quantum order, meaning a finite number of ground states which are locally indistinguishable, a finite spectral gap and first excited states with anyonic statistics. Moreover, we construct examples (all of them with local dimension smaller than 10) for which the threshold size L can occur at essentially any order of magnitude. From sizes that are reachable within current experimental setups and numerical simulations (L=15 or L=84) to sizes that are beyond any present or future capability, such as L> 10^35000.

2015 APS Fellows Nominated by GQI

Congratulations to the 2015 APS fellows nominated by GQI.
Cory, David [2015]
University of Waterloo
Citation: For pioneering one of the first demonstrations of a quantum computer using magnetic moments of nuclei as quantum bits and identifying new industrial applications in medicine, oil exploration and pharmaceuticals.
Englert, Berge [2015]
National University of Singapore
Citation: For distinctive theoretical contributions to the foundations, interpretation, and applications of quantum mechanics.
Nemoto, Kae [2015]
National Institute of Academic Degree
Citation: For pioneering the theory for quantum optical implementations of quantum information processing and communication.
Tahan, Charles [2015]
Lab for Physical Sciences
Citation: For important contributions to the field of quantum information science, including theoretical work advancing the experimental development of silicon quantum computers and proposing new quantum devices in the solid state.
Walther, Philip [2015]
No Company Provided
Citation: For outstanding achievements in experimental quantum information, quantum optics, and quantum photonics; including the first realization of privacy-preserving quantum cloud computing and the first experimental verification of a quantum computation.

Quantum Foundations Workshop 2015

In order to celebrate the 90th anniversary of quantum mechanics, the International Journal of Quantum Foundations (IJQF), will host an online Workshop on Quantum Foundations from 9th July 2015 to 19th July 2015. The workshop will bring together leading experts in the field, and address the most pressing problems in the foundations of quantum mechanics today.

Based on the successful experience from First iWorkshop on the Meaning of the Wave Function and John Bell Workshop 2014, this workshop will be more self-organized. Every participant may create a topic in the workshop forum on his own, which attaches his paper and gives a concise introduction to his ideas to be discussed, and which also states the date and time of his two-hour discussion. Then other participants can leave comments beforehand or participate in the discussions by text chat in the forum in the two-hour duration at the time.

For more information, visit the Workshop’s website.

Welcome to the “new” Quantum Times

After much delay, it is my pleasure to announce the newest incarnation of The Quantum Times. In its new format, readers can submit articles, conference announcements, and job postings (see “Submit A Post” tab above) that will then be reviewed, possibly edited, and finally posted. Any major edits will be cleared with the author prior to posting. The aim is to dramatically speed up the time it takes for an item to appear in The Times. The only drawback is that there will no longer be regular issues. Rather, it will be a “continuous” publication.

The key is for The Times to become a community site for quantum information and foundations, and to encourage active participation in the APS’ GQI, which is very close to attaining division status. As GQI is the world’s largest organization dedicated solely to quantum information, this represents the natural evolution of The Times which started out as the group’s newsletter in 2006.

We would like to thank Matt Leifer for his technical assistance with setting this site up. We would also like to thank the Executive Committee and Editorial Board for their support and patience during this transition.

Remember that this site relies on your submissions! We look forward to hearing from you!

Newsletter of the APS Topical Group on Quantum Information