Tag Archives: entanglement

Brain stuff: quantum entanglement and a multi-dimensional universe

I have two brain news bits, one about neural networks and quantum entanglement and another about how the brain operates on more than three dimensions.

Quantum entanglement and neural networks

A June 13, 2017 news item on phys.org describes how machine learning can be used to solve problems in physics (Note: Links have been removed),

Machine learning, the field that’s driving a revolution in artificial intelligence, has cemented its role in modern technology. Its tools and techniques have led to rapid improvements in everything from self-driving cars and speech recognition to the digital mastery of an ancient board game.

Now, physicists are beginning to use machine learning tools to tackle a different kind of problem, one at the heart of quantum physics. In a paper published recently in Physical Review X, researchers from JQI [Joint Quantum Institute] and the Condensed Matter Theory Center (CMTC) at the University of Maryland showed that certain neural networks—abstract webs that pass information from node to node like neurons in the brain—can succinctly describe wide swathes of quantum systems.

An artist’s rendering of a neural network with two layers. At the top is a real quantum system, like atoms in an optical lattice. Below is a network of hidden neurons that capture their interactions (Credit: E. Edwards/JQI)

A June 12, 2017 JQI news release by Chris Cesare, which originated the news item, describes how neural networks can represent quantum entanglement,

Dongling Deng, a JQI Postdoctoral Fellow who is a member of CMTC and the paper’s first author, says that researchers who use computers to study quantum systems might benefit from the simple descriptions that neural networks provide. “If we want to numerically tackle some quantum problem,” Deng says, “we first need to find an efficient representation.”

On paper and, more importantly, on computers, physicists have many ways of representing quantum systems. Typically these representations comprise lists of numbers describing the likelihood that a system will be found in different quantum states. But it becomes difficult to extract properties or predictions from a digital description as the number of quantum particles grows, and the prevailing wisdom has been that entanglement—an exotic quantum connection between particles—plays a key role in thwarting simple representations.

The neural networks used by Deng and his collaborators—CMTC Director and JQI Fellow Sankar Das Sarma and Fudan University physicist and former JQI Postdoctoral Fellow Xiaopeng Li—can efficiently represent quantum systems that harbor lots of entanglement, a surprising improvement over prior methods.

What’s more, the new results go beyond mere representation. “This research is unique in that it does not just provide an efficient representation of highly entangled quantum states,” Das Sarma says. “It is a new way of solving intractable, interacting quantum many-body problems that uses machine learning tools to find exact solutions.”

Neural networks and their accompanying learning techniques powered AlphaGo, the computer program that beat some of the world’s best Go players last year (link is external) (and the top player this year (link is external)). The news excited Deng, an avid fan of the board game. Last year, around the same time as AlphaGo’s triumphs, a paper appeared that introduced the idea of using neural networks to represent quantum states (link is external), although it gave no indication of exactly how wide the tool’s reach might be. “We immediately recognized that this should be a very important paper,” Deng says, “so we put all our energy and time into studying the problem more.”

The result was a more complete account of the capabilities of certain neural networks to represent quantum states. In particular, the team studied neural networks that use two distinct groups of neurons. The first group, called the visible neurons, represents real quantum particles, like atoms in an optical lattice or ions in a chain. To account for interactions between particles, the researchers employed a second group of neurons—the hidden neurons—which link up with visible neurons. These links capture the physical interactions between real particles, and as long as the number of connections stays relatively small, the neural network description remains simple.

Specifying a number for each connection and mathematically forgetting the hidden neurons can produce a compact representation of many interesting quantum states, including states with topological characteristics and some with surprising amounts of entanglement.

Beyond its potential as a tool in numerical simulations, the new framework allowed Deng and collaborators to prove some mathematical facts about the families of quantum states represented by neural networks. For instance, neural networks with only short-range interactions—those in which each hidden neuron is only connected to a small cluster of visible neurons—have a strict limit on their total entanglement. This technical result, known as an area law, is a research pursuit of many condensed matter physicists.

These neural networks can’t capture everything, though. “They are a very restricted regime,” Deng says, adding that they don’t offer an efficient universal representation. If they did, they could be used to simulate a quantum computer with an ordinary computer, something physicists and computer scientists think is very unlikely. Still, the collection of states that they do represent efficiently, and the overlap of that collection with other representation methods, is an open problem that Deng says is ripe for further exploration.

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

Quantum Entanglement in Neural Network States by Dong-Ling Deng, Xiaopeng Li, and S. Das Sarma. Phys. Rev. X 7, 021021 – Published 11 May 2017

This paper is open access.

Blue Brain and the multidimensional universe

Blue Brain is a Swiss government brain research initiative which officially came to life in 2006 although the initial agreement between the École Politechnique Fédérale de Lausanne (EPFL) and IBM was signed in 2005 (according to the project’s Timeline page). Moving on, the project’s latest research reveals something astounding (from a June 12, 2017 Frontiers Publishing press release on EurekAlert),

For most people, it is a stretch of the imagination to understand the world in four dimensions but a new study has discovered structures in the brain with up to eleven dimensions – ground-breaking work that is beginning to reveal the brain’s deepest architectural secrets.

Using algebraic topology in a way that it has never been used before in neuroscience, a team from the Blue Brain Project has uncovered a universe of multi-dimensional geometrical structures and spaces within the networks of the brain.

The research, published today in Frontiers in Computational Neuroscience, shows that these structures arise when a group of neurons forms a clique: each neuron connects to every other neuron in the group in a very specific way that generates a precise geometric object. The more neurons there are in a clique, the higher the dimension of the geometric object.

“We found a world that we had never imagined,” says neuroscientist Henry Markram, director of Blue Brain Project and professor at the EPFL in Lausanne, Switzerland, “there are tens of millions of these objects even in a small speck of the brain, up through seven dimensions. In some networks, we even found structures with up to eleven dimensions.”

Markram suggests this may explain why it has been so hard to understand the brain. “The mathematics usually applied to study networks cannot detect the high-dimensional structures and spaces that we now see clearly.”

If 4D worlds stretch our imagination, worlds with 5, 6 or more dimensions are too complex for most of us to comprehend. This is where algebraic topology comes in: a branch of mathematics that can describe systems with any number of dimensions. The mathematicians who brought algebraic topology to the study of brain networks in the Blue Brain Project were Kathryn Hess from EPFL and Ran Levi from Aberdeen University.

“Algebraic topology is like a telescope and microscope at the same time. It can zoom into networks to find hidden structures – the trees in the forest – and see the empty spaces – the clearings – all at the same time,” explains Hess.

In 2015, Blue Brain published the first digital copy of a piece of the neocortex – the most evolved part of the brain and the seat of our sensations, actions, and consciousness. In this latest research, using algebraic topology, multiple tests were performed on the virtual brain tissue to show that the multi-dimensional brain structures discovered could never be produced by chance. Experiments were then performed on real brain tissue in the Blue Brain’s wet lab in Lausanne confirming that the earlier discoveries in the virtual tissue are biologically relevant and also suggesting that the brain constantly rewires during development to build a network with as many high-dimensional structures as possible.

When the researchers presented the virtual brain tissue with a stimulus, cliques of progressively higher dimensions assembled momentarily to enclose high-dimensional holes, that the researchers refer to as cavities. “The appearance of high-dimensional cavities when the brain is processing information means that the neurons in the network react to stimuli in an extremely organized manner,” says Levi. “It is as if the brain reacts to a stimulus by building then razing a tower of multi-dimensional blocks, starting with rods (1D), then planks (2D), then cubes (3D), and then more complex geometries with 4D, 5D, etc. The progression of activity through the brain resembles a multi-dimensional sandcastle that materializes out of the sand and then disintegrates.”

The big question these researchers are asking now is whether the intricacy of tasks we can perform depends on the complexity of the multi-dimensional “sandcastles” the brain can build. Neuroscience has also been struggling to find where the brain stores its memories. “They may be ‘hiding’ in high-dimensional cavities,” Markram speculates.

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About Blue Brain

The aim of the Blue Brain Project, a Swiss brain initiative founded and directed by Professor Henry Markram, is to build accurate, biologically detailed digital reconstructions and simulations of the rodent brain, and ultimately, the human brain. The supercomputer-based reconstructions and simulations built by Blue Brain offer a radically new approach for understanding the multilevel structure and function of the brain. http://bluebrain.epfl.ch

About Frontiers

Frontiers is a leading community-driven open-access publisher. By taking publishing entirely online, we drive innovation with new technologies to make peer review more efficient and transparent. We provide impact metrics for articles and researchers, and merge open access publishing with a research network platform – Loop – to catalyse research dissemination, and popularize research to the public, including children. Our goal is to increase the reach and impact of research articles and their authors. Frontiers has received the ALPSP Gold Award for Innovation in Publishing in 2014. http://www.frontiersin.org.

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

Cliques of Neurons Bound into Cavities Provide a Missing Link between Structure and Function by Michael W. Reimann, Max Nolte, Martina Scolamiero, Katharine Turner, Rodrigo Perin, Giuseppe Chindemi, Paweł Dłotko, Ran Levi, Kathryn Hess, and Henry Markram. Front. Comput. Neurosci., 12 June 2017 | https://doi.org/10.3389/fncom.2017.00048

This paper is open access.

An atom without properties?

There’s rather intriguing Swiss research into atoms and so-called Bell Correlations according to an April 21, 2016 news item on ScienceDaily,

The microscopic world is governed by the rules of quantum mechanics, where the properties of a particle can be completely undetermined and yet strongly correlated with those of other particles. Physicists from the University of Basel have observed these so-called Bell correlations for the first time between hundreds of atoms. Their findings are published in the scientific journal Science.

Everyday objects possess properties independently of each other and regardless of whether we observe them or not. Einstein famously asked whether the moon still exists if no one is there to look at it; we answer with a resounding yes. This apparent certainty does not exist in the realm of small particles. The location, speed or magnetic moment of an atom can be entirely indeterminate and yet still depend greatly on the measurements of other distant atoms.

An April 21, 2016 University of Basel (Switzerland) press release (also on EurekAlert), which originated the news item, provides further explanation,

With the (false) assumption that atoms possess their properties independently of measurements and independently of each other, a so-called Bell inequality can be derived. If it is violated by the results of an experiment, it follows that the properties of the atoms must be interdependent. This is described as Bell correlations between atoms, which also imply that each atom takes on its properties only at the moment of the measurement. Before the measurement, these properties are not only unknown – they do not even exist.

A team of researchers led by professors Nicolas Sangouard and Philipp Treutlein from the University of Basel, along with colleagues from Singapore, have now observed these Bell correlations for the first time in a relatively large system, specifically among 480 atoms in a Bose-Einstein condensate. Earlier experiments showed Bell correlations with a maximum of four light particles or 14 atoms. The results mean that these peculiar quantum effects may also play a role in larger systems.

Large number of interacting particles

In order to observe Bell correlations in systems consisting of many particles, the researchers first had to develop a new method that does not require measuring each particle individually – which would require a level of control beyond what is currently possible. The team succeeded in this task with the help of a Bell inequality that was only recently discovered. The Basel researchers tested their method in the lab with small clouds of ultracold atoms cooled with laser light down to a few billionths of a degree above absolute zero. The atoms in the cloud constantly collide, causing their magnetic moments to become slowly entangled. When this entanglement reaches a certain magnitude, Bell correlations can be detected. Author Roman Schmied explains: “One would expect that random collisions simply cause disorder. Instead, the quantum-mechanical properties become entangled so strongly that they violate classical statistics.”

More specifically, each atom is first brought into a quantum superposition of two states. After the atoms have become entangled through collisions, researchers count how many of the atoms are actually in each of the two states. This division varies randomly between trials. If these variations fall below a certain threshold, it appears as if the atoms have ‘agreed’ on their measurement results; this agreement describes precisely the Bell correlations.

New scientific territory

The work presented, which was funded by the National Centre of Competence in Research Quantum Science and Technology (NCCR QSIT), may open up new possibilities in quantum technology; for example, for generating random numbers or for quantum-secure data transmission. New prospects in basic research open up as well: “Bell correlations in many-particle systems are a largely unexplored field with many open questions – we are entering uncharted territory with our experiments,” says Philipp Treutlein.

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

Bell correlations in a Bose-Einstein condensate by Roman Schmied, Jean-Daniel Bancal, Baptiste Allard, Matteo Fadel, Valerio Scarani, Philipp Treutlein, Nicolas Sangouard. Science  22 Apr 2016: Vol. 352, Issue 6284, pp. 441-444 DOI: 10.1126/science.aad8665

This paper is behind a paywall.

Viewing quantum entanglement with the naked eye

A Feb. 18, 2016 article by Bob Yirka for phys.org suggests there may be a way to see quantum entanglement with the naked eye,

A trio of physicists in Europe has come up with an idea that they believe would allow a person to actually witness entanglement. Valentina Caprara Vivoli, with the University of Geneva, Pavel Sekatski, with the University of Innsbruck and Nicolas Sangouard, with the University of Basel, have together written a paper describing a scenario where a human subject would be able to witness an instance of entanglement—they have uploaded it to the arXiv server for review by others.
Entanglement, is of course, where two quantum particles are intrinsically linked to the extent that they actually share the same existence, even though they can be separated and moved apart. The idea was first proposed nearly a century ago, and it has not only been proven, but researchers routinely cause it to occur, but, to date, not one single person has every actually seen it happen—they only know it happens by conducting a series of experiments. It is not clear if anyone has ever actually tried to see it happen, but in this new effort, the research trio claim to have found a way to make it happen—if only someone else will carry out the experiment on a willing volunteer.

A Feb. 17, 2016 article for the MIT (Massachusetts Institute of Technology) Technology Review describes this proposed project in detail,

Finding a way for a human eye to detect entangled photons sounds straightforward. After all, the eye is a photon detector, so it ought to be possible for an eye to replace a photo detector in any standard entanglement detecting experiment.

Such an experiment might consist of a source of entangled pairs of photons, each of which is sent to a photo detector via an appropriate experimental setup.

By comparing the arrival of photons at each detector and by repeating the detecting process many times, it is possible to determine statistically whether entanglement is occurring.

It’s easy to imagine that this experiment can be easily repeated by replacing one of the photodetectors with an eye. But that turns out not to be the case.

The main problem is that the eye cannot detect single photons. Instead, each light-detecting rod at the back of the eye must be stimulated by a good handful of photons to trigger a detection. The lowest number of photons that can do the trick is thought to be about seven, but in practice, people usually see photons only when they arrive in the hundreds or thousands.

Even then, the eye is not a particularly efficient photodetector. A good optics lab will have photodetectors that are well over 90 percent efficient. By contrast, at the very lowest light levels, the eye is about 8 percent efficient. That means it misses lots of photons.

That creates a significant problem. If a human eye is ever to “see” entanglement in this way, then physicists will have to entangle not just two photons but at least seven, and ideally many hundreds or thousands of them.

And that simply isn’t possible with today’s technology. At best, physicists are capable of entangling half a dozen photons but even this is a difficult task.

But the researchers have come up with a solution to the problem,

Vivoli and co say they have devised a trick that effectively amplifies a single entangled photon into many photons that the eye can see. Their trick depends on a technique called a displacement operation, in which two quantum objects interfere so that one changes the phase of another.

One way to do this with photons is with a beam splitter. Imagine a beam of coherent photons from a laser that is aimed at a beam splitter. The beam is transmitted through the splitter but a change of phase can cause it to be reflected instead.

Now imagine another beam of coherent photons that interferes with the first. This changes the phase of the first beam so that it is reflected rather than transmitted. In other words, the second beam can switch the reflection on and off.

Crucially, the switching beam needn’t be as intense as the main beam—it only needs to be coherent. Indeed, a single photon can do this trick of switching more intense beam, at least in theory.

That’s the basis of the new approach. The idea is to use a single entangled photon to switch the passage of more powerful beam through a beam splitter. And it is this more powerful beam that the eye detects and which still preserves the quantum nature of the original entanglement.

… this experiment will be hard to do. Ensuring that the optical amplifier works as they claim will be hard, for example.

And even if it does, reliably recording each detection in the eye will be even harder. The test for entanglement is a statistical one that requires many counts from both detectors. That means an individual would have to sit in the experiment registering a yes or no answer for each run, repeated thousands or tens of thousands of times. Volunteers will need to have plenty of time on their hands.

Of course, experiments like this will quickly take the glamor and romance out of the popular perception of entanglement. Indeed, it’s hard to see why anybody would want to be entangled with a photodetector over the time it takes to do this experiment.

There is a suggestion as to how to make this a more attractive proposition for volunteers,

One way to increase this motivation would be to modify the experiment so that it entangles two humans. It’s not hard to imagine a people wanting to take part in such an experiment, perhaps even eagerly.

That will require a modified set up in which both detectors are human eyes, with their high triggering level and their low efficiency. Whether this will be possible with Vivoli and co’s setup isn’t yet clear.

Only then will volunteers be able to answer the question that sits uncomfortably with most physicists. What does it feel like to be entangled with another human?

Given the nature of this experiment, the answer will be “mind-numbingly boring.” But as Vivoli and co point out in their conclusion: “It is safe to say that probing human vision with quantum light is terra incognita. This makes it an attractive challenge on its own.”

You can read the arXiv paper,

What Does It Take to See Entanglement? by Valentina Caprara Vivoli, Pavel Sekatski, Nicolas Sangouard arxiv.org/abs/1602.01907 Submitted Feb. 5, 2016

This is an open access paper and this site encourages comments and peer review.

One final comment, the articles reminded me of a March 1, 2012 posting which posed this question Can we see entangled images? a question for physicists in the headline for a piece about a physicist’s (Geraldo Barbosa) challenge and his arXiv paper. Coincidentally, the source article was by Bob Yirka and was published on phys.org.

Star Trek, Schrödinger’s cat, quantum entanglement, and more in memory teleportation scheme

A Jan. 13, 2016 news item on Nanowerk introduces Star Trek and Schrödinger’s cat as means to explain a quantum teleportation theory (Note: A link has been removed),

In “Star Trek”, a transporter can teleport a person from one location to a remote location without actually making the journey along the way. Such a transporter has fascinated many people. Quantum teleportation shares several features of the transporter and is one of the most important protocols in quantum information.

In a recent study (“Quantum superposition, entanglement, and state teleportation of a microorganism on an electromechanical oscillator”), Prof. Tongcang Li at Purdue University [US] and Dr. Zhang-qi Yin at Tsinghua University [China] proposed the first scheme to use electromechanical oscillators and superconducting circuits to teleport the internal quantum state (memory) and center-of-mass motion state of a microorganism.

They also proposed a scheme to create a Schrödinger’s cat state in which a microorganism can be in two places at the same time. This is an important step towards potentially teleporting an organism in future.

A Jan. 13, 2016 Science China Press news release on EurekAlert, which originated the news item, expands on the theme,

In 1935, Erwin Schrödinger proposed a famous thought experiment to prepare a cat in a superposition of both alive and dead states. The possibility of an organism to be in a superposition state dramatically reveals the profound consequences of quantum mechanics, and has attracted broad interests. Physicists have made great efforts in many decades to investigate macroscopic quantum phenomena. So far, matter-wave interference of electrons, atoms, and molecules (such as C60) have been observed. Recently, quantum ground state cooling and the creation of superposition states of mechanical oscillators have been realized. For example, a group in Colorado, US has cooled the vibration of a 15-micrometer-diameter aluminum membrane to quantum ground state, and entangled its motion with microwave photons. However, quantum superposition of an entire organism has not been realized. Meanwhile, there have been many breakthroughs in quantum teleportation since its first experimental realization in 1997 with a single photon. Besides photons, quantum teleportation with atoms, ions, and superconducting circuits have been demonstrated. In 2015, a group at University of Science and Technology of China demonstrated the quantum teleportation of multiple degrees of freedom of a single photon. However, existing experiments are still far away from teleporting an organism or the state of an organism.

In a recent study, Tongcang Li and Zhang-qi Yin propose to put a bacterium on top of an electromechanical membrane oscillator integrated with a superconducting circuit to prepare quantum superposition state of a microorganism and teleport its quantum state. A microorganism with a mass much smaller than the mass of the electromechanical membrane will not significantly affect the quality factor of the membrane and can be cooled to the quantum ground state together with the membrane. Quantum superposition and teleportation of its center-of-mass motion state can be realized with the help of superconducting microwave circuits. With a strong magnetic field gradient, the internal states of a microorganism, such as the electron spin of a glycine radical, can be entangled with its center-of-mass motion and be teleported to a remote microorganism. Since internal states of an organism contain information, this proposal provides a scheme for teleporting information or memories between two remote organisms.

The proposed setup is also a quantum-limited magnetic resonance force microscope. It not only can detect the existence of single electron spins (associated to protein defects or DNA defects) like conventional MRFM, but also can coherently manipulate and detect the quantum states of electron spins. It enables some isolated electron spins that could not be read out with optical or electrical methods to be used as quantum memory for quantum information.

Li says “We propose a straightforward method to put a microorganism in two places at the same time, and provide a scheme to teleport the quantum state of a microorganism. I hope our unconventional work will inspire more people to think seriously about quantum teleportation of a microorganism and its potential applications in future.” Yin says “Our work also provides insights for future studies about the effects of biochemical reactions in the wave function collapses of quantum superposition states of an organism.”

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

Quantum superposition, entanglement, and state teleportation of a microorganism on an electromechanical oscillator by Tongcang Li and Zhang-Qi Yin. Science Bulletin pp 1-9 DOI: 10.1007/s11434-015-0990-x First online: 11 January 2016

This paper is behind a paywall.

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.

Entangling thousands of atoms

Quantum entanglement as an idea seems extraordinary to me like something from of the fevered imagination made possible only with certain kinds of hallucinogens. I suppose you could call theoretical physicists who’ve conceptualized entanglement a different breed as they don’t seem to need chemical assistance for their flights of fancy, which turn out to be reality. Researchers at MIT (Massachusetts Institute of Technology) and the University of Belgrade (Serbia) have entangled thousands of atoms with a single photon according to a March 26, 2015 news item on Nanotechnology Now,

Physicists from MIT and the University of Belgrade have developed a new technique that can successfully entangle 3,000 atoms using only a single photon. The results, published today in the journal Nature, represent the largest number of particles that have ever been mutually entangled experimentally.

The researchers say the technique provides a realistic method to generate large ensembles of entangled atoms, which are key components for realizing more-precise atomic clocks.

“You can make the argument that a single photon cannot possibly change the state of 3,000 atoms, but this one photon does — it builds up correlations that you didn’t have before,” says Vladan Vuletic, the Lester Wolfe Professor in MIT’s Department of Physics, and the paper’s senior author. “We have basically opened up a new class of entangled states we can make, but there are many more new classes to be explored.”

A March 26, 2015 MIT news release by Jennifer Chu (also on EurekAlert but dated March 25, 2015), which originated the news item, describes entanglement with particular attention to how it relates to atomic timekeeping,

Entanglement is a curious phenomenon: As the theory goes, two or more particles may be correlated in such a way that any change to one will simultaneously change the other, no matter how far apart they may be. For instance, if one atom in an entangled pair were somehow made to spin clockwise, the other atom would instantly be known to spin counterclockwise, even though the two may be physically separated by thousands of miles.

The phenomenon of entanglement, which physicist Albert Einstein once famously dismissed as “spooky action at a distance,” is described not by the laws of classical physics, but by quantum mechanics, which explains the interactions of particles at the nanoscale. At such minuscule scales, particles such as atoms are known to behave differently from matter at the macroscale.

Scientists have been searching for ways to entangle not just pairs, but large numbers of atoms; such ensembles could be the basis for powerful quantum computers and more-precise atomic clocks. The latter is a motivation for Vuletic’s group.

Today’s best atomic clocks are based on the natural oscillations within a cloud of trapped atoms. As the atoms oscillate, they act as a pendulum, keeping steady time. A laser beam within the clock, directed through the cloud of atoms, can detect the atoms’ vibrations, which ultimately determine the length of a single second.

“Today’s clocks are really amazing,” Vuletic says. “They would be less than a minute off if they ran since the Big Bang — that’s the stability of the best clocks that exist today. We’re hoping to get even further.”

The accuracy of atomic clocks improves as more and more atoms oscillate in a cloud. Conventional atomic clocks’ precision is proportional to the square root of the number of atoms: For example, a clock with nine times more atoms would only be three times as accurate. If these same atoms were entangled, a clock’s precision could be directly proportional to the number of atoms — in this case, nine times as accurate. The larger the number of entangled particles, then, the better an atomic clock’s timekeeping.

It seems weak lasers make big entanglements possible (from the news release),

Scientists have so far been able to entangle large groups of atoms, although most attempts have only generated entanglement between pairs in a group. Only one team has successfully entangled 100 atoms — the largest mutual entanglement to date, and only a small fraction of the whole atomic ensemble.

Now Vuletic and his colleagues have successfully created a mutual entanglement among 3,000 atoms, virtually all the atoms in the ensemble, using very weak laser light — down to pulses containing a single photon. The weaker the light, the better, Vuletic says, as it is less likely to disrupt the cloud. “The system remains in a relatively clean quantum state,” he says.

The researchers first cooled a cloud of atoms, then trapped them in a laser trap, and sent a weak laser pulse through the cloud. They then set up a detector to look for a particular photon within the beam. Vuletic reasoned that if a photon has passed through the atom cloud without event, its polarization, or direction of oscillation, would remain the same. If, however, a photon has interacted with the atoms, its polarization rotates just slightly — a sign that it was affected by quantum “noise” in the ensemble of spinning atoms, with the noise being the difference in the number of atoms spinning clockwise and counterclockwise.

“Every now and then, we observe an outgoing photon whose electric field oscillates in a direction perpendicular to that of the incoming photons,” Vuletic says. “When we detect such a photon, we know that must have been caused by the atomic ensemble, and surprisingly enough, that detection generates a very strongly entangled state of the atoms.”

Vuletic and his colleagues are currently using the single-photon detection technique to build a state-of-the-art atomic clock that they hope will overcome what’s known as the “standard quantum limit” — a limit to how accurate measurements can be in quantum systems. Vuletic says the group’s current setup may be a step toward developing even more complex entangled states.

“This particular state can improve atomic clocks by a factor of two,” Vuletic says. “We’re striving toward making even more complicated states that can go further.”

This research was supported in part by the National Science Foundation, the Defense Advanced Research Projects Agency, and the Air Force Office of Scientific Research.

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

Entanglement with negative Wigner function of almost 3,000 atoms heralded by one photon by Robert McConnell, Hao Zhang, Jiazhong Hu, Senka Ćuk & Vladan Vuletić. Nature 519 439–442 (26 March 2015) doi:10.1038/nature14293 Published online 25 March 2015

This article is behind a paywall but there is a free preview via ReadCube Access.

This image illustrates the entanglement of a large number of atoms. The atoms, shown in purple, are shown mutually entangled with one another. Image: Christine Daniloff/MIT and Jose-Luis Olivares/MIT

This image illustrates the entanglement of a large number of atoms. The atoms, shown in purple, are shown mutually entangled with one another.
Image: Christine Daniloff/MIT and Jose-Luis Olivares/MIT

Science for your imagination

David Bruggeman over on his Pasco Phronesis has two postings which highlight different approaches to communicating about science. His Aug. 31, 2014 posting features audio plays (Note: Links have been removed),

L.A. Theatre Works makes a large number of their works available via audio. Its Relativity series (H/T Scirens) is a collection of (at this writing) 25 plays with science and technology either as themes and/or as forces driving the action of the play. You’re certainly familiar with War of the Worlds, and you may have heard of the plays Arcadia and Copenhagen. The science covered in these plays is from a number of different fields, and some works will try to engage the audience on the social implications of how science is conducted. The casts have many familiar faces as well. …

You can find the Relativity Series website here where the home page features these (amongst others),

COMPLETENESS

Jason Ritter and Mandy Siegfried star in a new play about love between gun-shy young scientists.

BREAKING THE CODE

The story of Alan Turing, an early pioneer in computer science, and his struggle to live authentically while serving his country.

THE DOCTOR’S DILEMMA

A respected physician must choose between the lives of two terminally ill men in George Bernard Shaw’s sharp-tongued satire of the medical profession.

THE EXPLORERS CLUB

It’s London, 1879, and the members of the Explorers Club must confront their most lethal threat yet: the admission of a woman into their scientific ranks.

THE GREAT TENNESSEE MONKEY TRIAL

The Scopes Monkey Trial of 1925 comes to life as William Jennings Bryan and Clarence Darrow square off over human evolution and the divide between faith and science.

PHOTOGRAPH 51

Miriam Margolyes stars as Rosalind Franklin, whose work led directly to the discovery of the DNA “double helix.”

DOCTOR CERBERUS

A teenage misfit is coming of age in the comforting glow of late-night horror movies. But when reality begins to intrude on his fantasy world, he realizes that hiding in the closet is no longer an option.

David’s Aug. 26, 2014 posting features Hieroglyph, a project from Arizona State University’s (ASU) Center for Science and the Imagination (Note: A link has been removed),

Next month [Sept. 2014] William Morrow will release Hieroglyph, a collection of science fiction short stories edited by the Director of the Center for Science and the Imagination at Arizona State University.  The name of the collection is taken from a theory advanced by science fiction writer Neil [Neal] Stephenson, and a larger writing project of which this book is a part.  The Hieroglyph Theory describes the kind of science fiction that can motivate scientists and engineers to create a future.  A Hieroglyph story provides a complete picture of the future, with a compelling innovation as part of that future.  An example would be the Asimov model of robotics.

Heiroglyph was first mentioned here in a May 7, 2013 posting,

The item which moved me to publish today (May 7, 2013), Can Science Fiction Writers Inspire The World To Save Itself?, by Ariel Schwartz concerns the Hieroglyph project at Arizona State University,

Humanity’s lack of a positive vision for the future can be blamed in part on an engineering culture that’s more focused on incrementalism (and VC funding) than big ideas. But maybe science fiction writers should share some of the blame. That’s the idea that came out of a conversation in 2011 between science fiction author Neal Stephenson and Michael Crow, the president of Arizona State University.

If science fiction inspires scientists and engineers to create new things–Stephenson believes it can–then more visionary, realistic sci-fi stories can help create a better future. Hence the Hieroglyph experiment, launched this month as a collaborative website for researchers and writers. Many of the stories created on the platform will go into a HarperCollins anthology of fiction and non-fiction, set to be published in 2014.

As it turns out, William Morrow Books is a a HarperCollins imprint. You can read a bit more about the book and preview some of the contents from the Scribd.com Hieroglyph webpage which includes this table of contents (much better looking in the Scribd version),

CONTENTS
FOREWORD—
LAWRENCE M. KRAUSS vii
PREFACE: INNOVATION STARVATION—NEAL STEPHENSON xiii
ACKNOWLEDGMENTS xxi
INTRODUCTION: A BLUEPRINT FOR BETTER DREAMS—ED FINN AND KATHRYN CRAMER xxiii
ATMOSPHÆRA INCOGNITA—NEAL STEPHENSON 1
GIRL IN WAVE : WAVE IN GIRL—KATHLEEN ANN GOONAN 38
BY THE TIME WE GET TO ARIZONA—MADELINE ASHBY 74
THE MAN WHO SOLD THE MOON—CORY DOCTOROW 98
JOHNNY APPLEDRONE VS. THE FAA—LEE KONSTANTINOU 182
DEGREES OF FREEDOM—KARL SCHROEDER 206
TWO SCENARIOS FOR THE FUTURE OF SOLAR ENERGY—ANNALEE NEWITZ 243
A HOTEL IN ANTARCTICA—GEOFFREY A. LANDIS 254
PERIAPSIS—JAMES L. CAMBIAS 283
THE MAN WHO SOLD THE STARS—GREGORY BENFORD 307
ENTANGLEMENT—VANDANA SINGH 352
ELEPHANT ANGELS—BRENDA COOPER 398
COVENANT—ELIZABETH BEAR 421
QUANTUM TELEPATHY—RUDY RUCKER 436
TRANSITION GENERATION—DAVID BRIN 466
THE DAY IT ALL ENDED—CHARLIE JANE ANDERS 477
TALL TOWER—BRUCE STERLING 489
SCIENCE AND SCIENCE FICTION: AN INTERVIEW WITH PAUL DAVIES 515
ABOUT THE EDITORS 526
ABOUT THE CONTRIBUTORS 527

Good on the organizers for being able to follow through on their promise to have something published by HarperCollins in 2014.

This book is not ASU’s Center for Science and the Imagination’s only activity. In November 2014, Margaret Atwood, an internationally known Canadian novelist, will visit the center (from the center’s home page),

Internationally renowned novelist and environmental activist Margaret Atwood will visit Arizona State University this November to discuss the relationship between art and science, and the importance of creative writing and imagination for addressing social and environmental challenges.

Atwood’s visit will mark the launch of the Imagination and Climate Futures Initiative, a new collaborative venture at ASU among the Rob and Melani Walton Sustainability Solutions Initiatives, the Center for Science and the Imagination and the Virginia G. Piper Center for Creative Writing. Atwood, author of the MaddAddam trilogy of novels that have become central to the emerging literary genre of climate fiction, or “CliFi,” will offer the inaugural lecture for the initiative on Nov. 5.

“We are proud to welcome Margaret Atwood, one of the world’s most celebrated living writers, to ASU and engage her in these discussions around climate, science and creative writing,” said Jewell Parker Rhodes, founding artistic director for the Virginia G. Piper Center for Creative Writing and the Piper Endowed Chair at Arizona State University. “A poet, novelist, literary critic and essayist, Ms. Atwood epitomizes the creative and professional excellence our students aspire to achieve.”

Focusing in particular on CliFi, the Imagination and Climate Futures Initiative will explore how imaginative skills can be harnessed to create solutions to climate challenges, and question whether and how creative writing can affect political decisions and behavior by influencing our social, political and scientific imagination.

“ASU is a leader in exploring how creativity and the imagination drive the arts, sciences, engineering and humanities,” said Ed Finn, director of the Center for Science and the Imagination. “The Imagination and Climate Futures Initiative will use the thriving CliFi genre to ask the hard questions about our cultural relationship to climate change and offer compelling visions for sustainable futures.”

The multidisciplinary Initiative will bring together researchers, artists, writers, decision-makers and the public to engage in research projects, teaching activities and events at ASU and beyond. The three ASU programs behind the Imagination and Climate Futures Initiative have a track record for academic and public engagement around innovative programs, including the Sustainability Solutions Festival; Emerge; and the Desert Nights, Rising Stars Writers Conference.

“Imagining how the future could unfold in a climatically changing world is key to making good policy and governance decisions today,” said Manjana Milkoreit, a postdoctoral fellow with the Walton Sustainability Solutions Initiatives. “We need to know more about the nature of imagination, its relationship to scientific knowledge and the effect of cultural phenomena such as CliFi on our imaginative capabilities and, ultimately, our collective ability to create a safe and prosperous future.”

Kind of odd they don’t mention Atwood’s Canadian, eh?

There’s lots more on the page which features news bits and articles, as well as, event information. Coincidentally, another Canuck (assuming he retains his citizenship after several years in the US) visited the center on June 7, 2014 to participate in an event billed as ‘An evening with Nathan Fillion and friends;; serenity [Joss Whedon’s tv series and movie], softwire, and science of science fiction’. A June 21, 2014 piece (on the center home page) by Joey Eschrich describes the night in some detail,

Nathan Fillion may very well be the friendliest, most unpretentious spaceship captain, mystery-solving author and science fiction heartthrob in the known universe. The “ruggedly handsome” star of TV’s “Castle” was the delight of fans as he headlined a fundraiser on the Arizona State University campus in Tempe, June 7 [2014].

The “Serenity, Softwire, and the Science of Science Fiction” event, benefiting the ASU Department of English and advertised as an “intimate evening for a small group of 50 people,” included considerable face-time with Fillion, who in-person proved surprisingly similar to the witty, charming and compassionate characters he plays on television and in film.

Starring with Fillion in the ASU evening’s festivities were science fiction author PJ Haarsma (a close friend of Fillion’s) along with ASU professors Ed Finn, director of the Center for Science and the Imagination; Peter Goggin, a literacy expert in the Department of English and senior scholar with the Global Institute of Sustainability; and School of Earth and Space Exploration faculty Jim Bell, an astronomer, and Sara Imari Walker, an astrobiologist. In addition to the Department of English, sponsors included ASU’s College of Liberal Arts and Sciences and Center for Science and the Imagination.

The event began with each panelist explaining how he or she arrived at his or her respective careers, and whether science or science fiction played a role in that journey. All panelists pointed to reading and imagining as formational to their senses of themselves and their places in life.

A number of big questions were posed to the panelists: “What is the likelihood of life on other planets?” and “What is the physical practicality of traveling to other planets?” ASU scientists Bell and Walker deftly fielded these complex planetary inquiries, while Goggin and Finn explained how the intersection of science and humanities – embodied in science fiction books and film – encouraged children and scholars alike to think creatively about the future. Attendees reported that they found the conversation “intellectually stimulating and thought-provoking as well as fun and entertaining.”

During the ensuing discussion, Haarsma and Fillion bantered back and forth comically, as we are told they often do in real life, at one point raising the group’s awareness of the mission they have shared for many years: promoting reading in the lives of young people. The two founded the Kids Need to Read Foundation, which provides books to underserved schools and libraries. Fillion, the son of retired English teachers, attended Concordia University of Alberta [no], where he was a member of the Kappa Alpha Society, an organization that emphasizes literature and debate. His brother, Jeff, is a highly respected school principal. Fillion’s story about the importance of books and reading in his childhood home was a rare moment of seriousness for the actor.

The most delightful aspect of the evening, according to guests, was the good nature of Fillion himself, who arrived with Haarsma earlier than expected and stayed later than scheduled. Fillion spent several minutes with each individual or group of friends, laughing with them, using their phone cameras to snap group “selfies” and showing a genuine interest in getting to know them.

Audience members each received copies of science fiction books: Haarsma’s teen novel, “Softwire: Virus on Orbis I,” and the Tomorrow Project science fiction anthology “Cautions, Dreams & Curiosities,” which was co-produced by the Center for Science and the Imagination with Intel and the Society for Science & the Public. Guests presented their new books and assorted other items to Fillion and Haarsma for autographing and a bit more conversation before the evening came to a close. It was then time for Fillion to head back downtown to his hotel, but not before one cadre of friends “asked him to take one last group shot of us at the end of the night, to which he replied with a smile, ‘I thought you’d never ask.’”

Oops! Concordia University is in the province of Québec not Alberta which is home to the University of Calgary and the University of Alberta.

The evening with Nathan Fillion and friends was a fundraiser, participants were charged $250 each for one of 50 seats at the event, which means they raised $12,500 minus any expenses incurred. Good for them!

For anyone unfamiliar with P.J. Haarsma’s oeuvre, there’s this Wikipedia entry for The Softwire.

‘Entangling’ microscopic drum beats with electrical signals

Scientists at the US National Institute of Standards and Technology (NIST) have gotten closer to extending observations pf quantum entanglement into the macroscale (real life scale) according to an Oct. 3, 2013 news item on Nanowerk,

Extending evidence of quantum behavior farther into the large-scale world of everyday life, physicists at the National Institute of Standards and Technology (NIST) have “entangled” — linked the properties of — a microscopic mechanical drum with electrical signals. The results confirm that NIST’s micro-drum could be used as a quantum memory in future quantum computers, which would harness the rules of quantum physics to solve important problems that are intractable today. The work also marks the first-ever entanglement of a macroscopic oscillator, expanding the range of practical uses of the drum.

The Oct. 3, 2013 NIST news release, which originated the news item, describes how scientists are increasingly observing  and testing for entanglement at larger scales,

Entanglement is a curious feature of the quantum world once believed to occur only at atomic and smaller scales. In recent years, scientists have been finding it in larger systems. Entanglement has technological uses. For instance, it is essential for quantum computing operations such as correcting errors, and for quantum teleportation of data from one place to another.

The experiments, described Oct. 3, 2013, in Science Express,* were performed at JILA, a joint institute of NIST and the University of Colorado Boulder.

NIST introduced the aluminum micro-drum in 2011 and earlier this year suggested it might be able to store data in quantum computers.** The drum—just 15 micrometers in diameter and 100 nanometers thick—features both mechanical properties (such as vibrations) and quantum properties (such as the ability to store and transfer individual quanta of energy).

The drum is part of an electromechanical circuit that can exchange certain quantum states between the waveform of a microwave pulse and vibration in the drum. In the latest JILA experiment, a microwave signal “cooled” the drum to a very low energy level, just one unit of vibration, in a way analogous to some laser-cooling techniques. Then another signal caused the drum’s motion to become entangled with a microwave pulse that emerged spontaneously in the system.

The drum stored the quantum information in the form of vibrational energy for at least 10 microseconds, long enough to be useful in experiments. Then the same type of microwave signal that cooled the drum was used to transfer the state stored in the drum to a second microwave pulse.

Researchers measured the properties of the two microwave pulses—specific points on the curves of the travelling waves—and found that the results were strongly correlated over 10,000 repetitions of the experiment. The evidence of quantum entanglement comes from the fact that measuring the first microwave pulse allowed scientists to anticipate the characteristics of the second pulse with greater accuracy than would otherwise be expected. The correlations between the two pulses indicated that the first pulse was entangled with the drum and the second pulse encoded the drum’s quantum state.

The results suggest that the drum, in addition to its potential as a quantum memory device, also could be used to generate entanglement in microwaves, to convert one form of quantum information to an otherwise incompatible form, and to sense tiny forces with improved precision.

Here are two links to and citations for the researchers’ paper and for an article, respectively,,

* T.A. Palomaki, J.D. Teufel, R.W. Simmonds and K.W. Lehnert. Entangling mechanical motion with microwave fields. Science Express. Oct. 3, 2013. Science DOI: 10.1126/science.1244563
** See 2013 NIST Tech Beat article, “NIST Mechanical Micro-Drum Used as Quantum Memory,” at http://www.nist.gov/pml/div689/drum-031313.cfm.

The Science Express paper is behind a paywall and the NIST Tech Beat article is not avallable due to the US government shutdown.

This ‘entanglement’ news reminds me Geraldo Barbosa’s challenge about seeing quantum entanglement in every day life featured in my Mar. 1, 2012 posting,

You can find Barbosa’s paper/challenge, Can humans see beyond intensity images? here. The abstract presents the challenge this way,

The human’s visual system detect intensity images. Quite interesting, detector systems have shown the existence of different kind of images. Among them, images obtained by two detectors (detector array or spatially scanning detector) capturing signals within short window times may reveal a “hidden” image not contained in either isolated detector: Information on this image depend on the two detectors simultaneously. In general, they are called “high-order” images because they may depend on more than two electric fields. Intensity images depend on the square of magnitude of the light’s electric field. Can the human visual sensory system perceive high-order images as well? This paper proposes a way to test this idea. A positive answer could give new insights on the “visual-conscience” machinery, opening a new sensory channel for humans. Applications could be devised, e.g., head position sensing, privacy in communications at visual ranges and many others.

Space-time crystals and everlasting clocks

Apparently, a space-time crystal could be useful for such things as studying the many-body problem in physics.  Since I hadn’t realized the many-body problem existed and have no idea how this might affect me or anyone else, I will have to take the utility of a space-time crystal on trust.As for the possibility of an everlasting clock, how will I ever know the truth since I’m not everlasting?

The Sept. 24, 2012 news item on Nanowerk about a new development makes the space-time crystal sound quite fascinating,

Imagine a clock that will keep perfect time forever, even after the heat-death of the universe. This is the “wow” factor behind a device known as a “space-time crystal,” a four-dimensional crystal that has periodic structure in time as well as space. However, there are also practical and important scientific reasons for constructing a space-time crystal. With such a 4D crystal, scientists would have a new and more effective means by which to study how complex physical properties and behaviors emerge from the collective interactions of large numbers of individual particles, the so-called many-body problem of physics. A space-time crystal could also be used to study phenomena in the quantum world, such as entanglement, in which an action on one particle impacts another particle even if the two particles are separated by vast distances. [emphasis mine]

While I’m most interested in the possibility of studying entanglement, it seems to me the scientists are guessing since the verb ‘could’ is being used where they used ‘would’ previously for studying the many body problem.

The Sept. 24, 2012 news release by Lynn Yarris for the Lawrence Berkeley National Laboratory  (Berkeley Lab), which originated the news item, provides detail on the latest space-time crystal development,

A space-time crystal, however, has only existed as a concept in the minds of theoretical scientists with no serious idea as to how to actually build one – until now. An international team of scientists led by researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has proposed the experimental design of a space-time crystal based on an electric-field ion trap and the Coulomb repulsion of particles that carry the same electrical charge.

“The electric field of the ion trap holds charged particles in place and Coulomb repulsion causes them to spontaneously form a spatial ring crystal,” says Xiang Zhang, a faculty scientist  with Berkeley Lab’s Materials Sciences Division who led this research. “Under the application of a weak static magnetic field, this ring-shaped ion crystal will begin a rotation that will never stop. The persistent rotation of trapped ions produces temporal order, leading to the formation of a space-time crystal at the lowest quantum energy state.”

Because the space-time crystal is already at its lowest quantum energy state, its temporal order – or timekeeping – will theoretically persist even after the rest of our universe reaches entropy, thermodynamic equilibrium or “heat-death.”

This new development builds on some work done earlier this year at the Massachusetts Institute of Technology (MIT), from the Yarris news release,

The concept of a crystal that has discrete order in time was proposed earlier this year by Frank Wilczek, the Nobel-prize winning physicist at the Massachusetts Institute of Technology. While Wilczek mathematically proved that a time crystal can exist, how to physically realize such a time crystal was unclear. Zhang and his group, who have been working on issues with temporal order in a different system since September 2011, have come up with an experimental design to build a crystal that is discrete both in space and time – a space-time crystal.

Traditional crystals are 3D solid structures made up of atoms or molecules bonded together in an orderly and repeating pattern. Common examples are ice, salt and snowflakes. Crystallization takes place when heat is removed from a molecular system until it reaches its lower energy state. At a certain point of lower energy, continuous spatial symmetry breaks down and the crystal assumes discrete symmetry, meaning that instead of the structure being the same in all directions, it is the same in only a few directions.

“Great progress has been made over the last few decades in exploring the exciting physics of low-dimensional crystalline materials such as two-dimensional graphene, one-dimensional nanotubes, and zero-dimensional buckyballs,” says Tongcang Li, lead author of the PRL paper and a post-doc in Zhang’s research group. “The idea of creating a crystal with dimensions higher than that of conventional 3D crystals is an important conceptual breakthrough in physics and it is very exciting for us to be the first to devise a way to realize a space-time crystal.”

Just as a 3D crystal is configured at the lowest quantum energy state when continuous spatial symmetry is broken into discrete symmetry, so too is symmetry breaking expected to configure the temporal component of the space-time crystal. Under the scheme devised by Zhang and Li and their colleagues, a spatial ring of trapped ions in persistent rotation will periodically reproduce itself in time, forming a temporal analog of an ordinary spatial crystal. With a periodic structure in both space and time, the result is a space-time crystal.

Here’s an image created by team at the Berkeley Lab to represent their work on the space-time crystal,

Imagine a clock that will keep perfect time forever or a device that opens new dimensions into quantum phenomena such as emergence and entanglement. (courtesy of Xiang Zhang group[?] at Berkeley Lab)

For anyone who’s interested in this work, I suggest reading either the news item on Nanowerk or the Berkeley Lab news release in full. I will leave you with Natalie Cole and Everlasting Love,

Can we see entangled images? a question for physicists

This February 29, 2012 news item by Bob Yirka poses a challenge from a professor of electrical engineering and computing science to physicists everywhere (I have removed links from the excerpt) which may not be as farfetched as it seems initially,

Geraldo Barbosa, professor of electrical engineering and computer science at Northwestern University … wonders if the human eye and brain together are capable of actually seeing entangled images. This is not a philosophical question, as he has phrased the query as part of a practical experiment that someone with the proper lab could actually carry out. To that end, he’s posted a paper on the preprint server arXiv with the hope that a physics team will take up the challenge.

Some animals can see things in the infrared spectrum for example and evidence has been slowly emerging as described here, here and here, suggesting that some migrating birds are able to “see” the Earth’s magnetic field. So maybe it’s possible that we see entangled images every day, and just don’t know it.

You can find Barbosa’s paper/challenge, Can humans see beyond intensity images? here. The abstract presents the challenge this way,

The human’s visual system detect intensity images. Quite interesting, detector systems have shown the existence of different kind of images. Among them, images obtained by two detectors (detector array or spatially scanning detector) capturing signals within short window times may reveal a “hidden” image not contained in either isolated detector: Information on this image depend on the two detectors simultaneously. In general, they are called “high-order” images because they may depend on more than two electric fields. Intensity images depend on the square of magnitude of the light’s electric field. Can the human visual sensory system perceive high-order images as well? This paper proposes a way to test this idea. A positive answer could give new insights on the “visual-conscience” machinery, opening a new sensory channel for humans. Applications could be devised, e.g., head position sensing, privacy in communications at visual ranges and many others.

Good luck to everyone devising an experiment to test the ability to see entangled images.