Tag Archives: quantum entanglement

Nanodevices and quantum entanglement

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A May 30, 2016 news item on phys.org introduces a scientist with an intriguing approach to quantum computing,

Creating quantum computers which some people believe will be the next generation of computers, with the ability to outperform machines based on conventional technology—depends upon harnessing the principles of quantum mechanics, or the physics that governs the behavior of particles at the subatomic scale. Entanglement—a concept that Albert Einstein once called “spooky action at a distance”—is integral to quantum computing, as it allows two physically separated particles to store and exchange information.

Stevan Nadj-Perge, assistant professor of applied physics and materials science, is interested in creating a device that could harness the power of entangled particles within a usable technology. However, one barrier to the development of quantum computing is decoherence, or the tendency of outside noise to destroy the quantum properties of a quantum computing device and ruin its ability to store information.

Nadj-Perge, who is originally from Serbia, received his undergraduate degree from Belgrade University and his PhD from Delft University of Technology in the Netherlands. He received a Marie Curie Fellowship in 2011, and joined the Caltech Division of Engineering and Applied Science in January after completing postdoctoral appointments at Princeton and Delft.

He recently talked with us about how his experimental work aims to resolve the problem of decoherence.

A May 27, 2016 California Institute of Technology (CalTech) news release by Jessica Stoller-Conrad, which originated the news item, proceeds with a question and answer format,

What is the overall goal of your research?

A large part of my research is focused on finding ways to store and process quantum information. Typically, if you have a quantum system, it loses its coherent properties—and therefore, its ability to store quantum information—very quickly. Quantum information is very fragile and even the smallest amount of external noise messes up quantum states. This is true for all quantum systems. There are various schemes that tackle this problem and postpone decoherence, but the one that I’m most interested in involves Majorana fermions. These particles were proposed to exist in nature almost eighty years ago but interestingly were never found.

Relatively recently theorists figured out how to engineer these particles in the lab. It turns out that, under certain conditions, when you combine certain materials and apply high magnetic fields at very cold temperatures, electrons will form a state that looks exactly as you would expect from Majorana fermions. Furthermore, such engineered states allow you to store quantum information in a way that postpones decoherence.

How exactly is quantum information stored using these Majorana fermions?

The fascinating property of these particles is that they always come in pairs. If you can store information in a pair of Majorana fermions it will be protected against all of the usual environmental noise that affects quantum states of individual objects. The information is protected because it is not stored in a single particle but in the pair itself. My lab is developing ways to engineer nanodevices which host Majorana fermions. Hopefully one day our devices will find applications in quantum computing.

Why did you want to come to Caltech to do this work?

The concept of engineered Majorana fermions and topological protection was, to a large degree, conceived here at Caltech by Alexei Kiteav [Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics] who is in the physics department. A couple of physicists here at Caltech, Gil Refeal [professor of theoretical physics and executive officer of physics] and Jason Alicea [professor of theoretical physics], are doing theoretical work that is very relevant for my field.

Do you have any collaborations planned here?

Nothing formal, but I’ve been talking a lot with Gil and Jason. A student of mine also uses resources in the lab of Harry Atwater [Howard Hughes Professor of Applied Physics and Materials Science and director of the Joint Center for Artificial Photosynthesis], who has experience with materials that are potentially useful for our research.

How does that project relate to your lab’s work?

There are two-dimensional, or 2-D, materials that are basically very thin sheets of atoms. Graphene [emphasis mine]—a single layer of carbon atoms—is one example, but you can create single layer sheets of atoms with many materials. Harry Atwater’s group is working on solar cells made of a 2-D material. We are thinking of using the same materials and combining them with superconductors—materials that can conduct electricity without releasing heat, sound, or any other form of energy—in order to produce Majorana fermions.

How do you do that?

There are several proposed ways of using 2-D materials to create Majorana fermions. The majority of these materials have a strong spin-orbit coupling—an interaction of a particle’s spin with its motion—which is one of the key ingredients for creating Majoranas. Also some of the 2-D materials can become superconductors at low temperatures. One of the ideas that we are seriously considering is using a 2-D material as a substrate on which we could build atomic chains that will host Majorana fermions.

What got you interested in science when you were young?

I don’t come from a family of scientists; my father is an engineer and my mother is an administrative worker. But my father first got me interested in science. As an engineer, he was always solving something and he brought home some of the problems he was working. I worked with him and picked it up at an early age.

How are you adjusting to life in California?

Well, I like being outdoors, and here we have the mountains and the beach and it’s really amazing. The weather here is so much better than the other places I’ve lived. If you want to get the impression of what the weather in the Netherlands is like, you just replace the number of sunny days here with the number of rainy days there.

I wish Stevan Nadj-Perge good luck!

An atom without properties?

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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.

A demonstration of quantum surrealism

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The Canadian Institute for Advanced Research (CIFAR) has announced some intriguing new research results. A Feb. 19, 2016 news item on ScienceDaily gets the ball rolling,

New research demonstrates that particles at the quantum level can in fact be seen as behaving something like billiard balls rolling along a table, and not merely as the probabilistic smears that the standard interpretation of quantum mechanics suggests. But there’s a catch — the tracks the particles follow do not always behave as one would expect from “realistic” trajectories, but often in a fashion that has been termed “surrealistic.”

A Feb. 19, 2016 CIFAR news release by Kurt Kleiner, which originated the news item, offers the kind of explanation that allows an amateur such as myself to understand the principles (while I’m reading it), thank you Kurt Kleiner,

In a new version of an old experiment, CIFAR Senior Fellow Aephraim Steinberg (University of Toronto) and colleagues tracked the trajectories of photons as the particles traced a path through one of two slits and onto a screen. But the researchers went further, and observed the “nonlocal” influence of another photon that the first photon had been entangled with.

The results counter a long-standing criticism of an interpretation of quantum mechanics called the De Broglie-Bohm theory. Detractors of this interpretation had faulted it for failing to explain the behaviour of entangled photons realistically. For Steinberg, the results are important because they give us a way of visualizing quantum mechanics that’s just as valid as the standard interpretation, and perhaps more intuitive.

“I’m less interested in focusing on the philosophical question of what’s ‘really’ out there. I think the fruitful question is more down to earth. Rather than thinking about different metaphysical interpretations, I would phrase it in terms of having different pictures. Different pictures can be useful. They can help shape better intuitions.”

At stake is what is “really” happening at the quantum level. The uncertainty principle tells us that we can never know both a particle’s position and momentum with complete certainty. And when we do interact with a quantum system, for instance by measuring it, we disturb the system. So if we fire a photon at a screen and want to know where it will hit, we’ll never know for sure exactly where it will hit or what path it will take to get there.

The standard interpretation of quantum mechanics holds that this uncertainty means that there is no “real” trajectory between the light source and the screen. The best we can do is to calculate a “wave function” that shows the odds of the photon being in any one place at any time, but won’t tell us where it is until we make a measurement.

Yet another interpretation, called the De Broglie-Bohm theory, says that the photons do have real trajectories that are guided by a “pilot wave” that accompanies the particle. The wave is still probabilistic, but the particle takes a real trajectory from source to target. It doesn’t simply “collapse” into a particular location once it’s measured.

In 2011 Steinberg and his colleagues showed that they could follow trajectories for photons by subjecting many identical particles to measurements so weak that the particles were barely disturbed, and then averaging out the information. This method showed trajectories that looked similar to classical ones — say, those of balls flying through the air.

But critics had pointed out a problem with this viewpoint. Quantum mechanics also tells us that two particles can be entangled, so that a measurement of one particle affects the other. The critics complained that in some cases, a measurement of one particle would lead to an incorrect prediction of the trajectory of the entangled particle. They coined the term “surreal trajectories” to describe them.

In the most recent experiment, Steinberg and colleagues showed that the surrealism was a consequence of non-locality — the fact that the particles were able to influence one another instantaneously at a distance. In fact, the “incorrect” predictions of trajectories by the entangled photon were actually a consequence of where in their course the entangled particles were measured. Considering both particles together, the measurements made sense and were consistent with real trajectories.

Steinberg points out that both the standard interpretation of quantum mechanics and the De Broglie-Bohm interpretation are consistent with experimental evidence, and are mathematically equivalent. But it is helpful in some circumstances to visualize real trajectories, rather than wave function collapses, he says.

An image illustrating the work has been provided,

On the left, a still image from an animation of reconstructed trajectories for photons going through a double-slit. A second photon “measures” which slit each photon traversed, so no interference results on the screen. The image on the right shows the polarisation of this second, “probe." Credit: Dylan Mahler Courtesy: CIFAR

On the left, a still image from an animation of reconstructed trajectories for photons going through a double-slit. A second photon “measures” which slit each photon traversed, so no interference results on the screen. The image on the right shows the polarisation of this second, “probe.” Credit: Dylan Mahler Courtesy: CIFAR

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

Experimental nonlocal and surreal Bohmian trajectories by Dylan H. Mahler, Lee Rozema, Kent Fisher, Lydia Vermeyden, Kevin J. Resch, Howard M. Wiseman, and Aephraim Steinberg. Science Advances  19 Feb 2016: Vol. 2, no. 2, e1501466 DOI: 10.1126/science.1501466

This article appears to be open access.

Viewing quantum entanglement with the naked eye

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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.

Entangling thousands of atoms

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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

TED 2014 ‘pre’ opening with reclaimed river, reforesting the world, open source molecular animation software, and a quantum butterfly

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Today, March 17, 2014 TED opened with the first of two sessions devoted to the 2014 TED fellows. The ones I’m choosing to describe in brief detail are those who most closely fall within this blog’s purview. My choices are not a reflection of my opinion about the speaker or the speaker’s topic or the importance of the topic.

First, here’s a list of the fellows* along with a link to their TED 2014 biography (list and links from the TED 2014 schedule),

Usman Riaz Percussive guitarist
Ziyah Gafić photographer + storyteller
Alexander McLean african prison activist
Dan Visconti composer + concert presenter
Aziza Chaouni architect + ecotourism specialist
Shubhendu Sharma reforestation expert
Bora Yoon Experimental musician
Aziz Abu Sarah entrepreneur + educator
Gabriella Gomez-Mont Creativity Officer, Guest Host
Jorge Mañes Rubio conceptual artist
Bora Yoon Experimental musician
Janet Iwasa molecular animator
Robert Simpson astronomer + web developer
Shohini Ghose quantum physicist + educator
Sergei Lupashin aerial robotics researcher + entrepreneur
Lars Jan director + media artist
Sarah Parcak Space archaeologist, TED Fellow [part of group presentation]
Tom Rielly Satirist [received a 5th anniversary gift, a muppet of himself from group]
Susie Ibarra composer + improviser + percussionist educator
Usman Riaz

Aziza Chaouni is an architect based in Morocco. From Fez (and I think she was born there), she is currently working to reclaim the Fez River, which she described as the ‘soul of the city’. As urbanization has taken over Fez, the river has been paved over as it has become more polluted with raw sewage being dumped into it along with industrial byproducts from tanning and other industries. As part of the project to reclaim the river, i.e., clean it and uncover it, Chaouni and her collaborators have created public spaces such as a playground which both cleanses the river and gives children a place to play which uncovering part of the city’s ‘soul’.

Shubhendu Sharma founded Afforestt with the intention of bringing forests which have been decimated not only in India but around the world. An engineer by training, he has adapted an industrial model used for car production to his forest-making endeavours. Working with his reforestation model, you can develop a forest with 300 trees in the space needed to park six cars and for less money than you need to buy an iPhone. The Afforestt project is about to go open-source meaning that anyone in the world can download the information necessary to create a forest.

Jorge Mañes Rubio spoke about his art project where he creates travel souvenirs, e.g., water from the near a submerged city in China. The city was submerged in the Three Gorges hydro dam project. For anyone not familiar with the project, from the Wikipedia Three Gorges Dam entry (Note: Links removed),

The Three Gorges Dam is a hydroelectric dam that spans the Yangtze River by the town of Sandouping, located in Yiling District, Yichang, Hubei province, China. The Three Gorges Dam is the world’s largest power station in terms of installed capacity (22,500 MW). In 2012, the amount of electricity the dam generated was similar to the amount generated by the Itaipu Dam. [2][3]

Except for a ship lift, the dam project was completed and fully functional as of July 4, 2012,[4][5] when the last of the main turbines in the underground plant began production. Each main turbine has a capacity of 700 MW.[3][6] The dam body was completed in 2006. Coupling the dam’s 32 main turbines with two smaller generators (50 MW each) to power the plant itself, the total electric generating capacity of the dam is 22,500 MW.[3][7][8]

The one souvenir he showed from that project featured symbols from traditional Chinese art festooned around the edges of white plastic bottle containing water from above a submerged Chinese city.

Janet Iwasa, a PhD in biochemistry, professor at the University of Utah and a molecular animator, talked about the animating molecular movement in and around cells. She showed an animation of a clathrin cage (there’s more about clathrin, a protein in a Wikipedia entry; looks a lot like a buckyball or buckminster fullerene except it’s not carbon) which provides a completely different understanding of how these are formed than is possible from still illustrations. She, along with her team, has created an open source software, Molecular Flipbook, which is available in in beta as of today, March 17, 2014.

The next session is starting. I’ll try and get back here to include more about Robert Simpson and Shohini Ghose.

ETa March 17, 2014 at 1521 PST:

Robert Simpson talked about citizen science, the Zooniverse project, and astronomy.  I have mentioned Zooniverse here (a Jan. 17, 2012 posting titled: Champagne galaxy, drawing bubbles for science and a Sept. 17, 2013 posting titled: Volunteer on the Plankton Portal and help scientists figure out ways to keep the ocean healthy.  Simpson says there are 1 million people participating in various Zooniverse projects and he mentioned that in addition to getting clicks and time from people, they’ve also gotten curiosity. That might seem obvious but he went on to describe a project (the Galaxy Zoo project) where the citizen scientists became curious about certain phenomena they were observing and as a consequence of their curiosity an entirely new type of galaxy was discovered, a pea galaxy. From the Pea Galaxy Wikipedia entry (Note: Links have been removed),

A Pea galaxy, also referred to as a Pea or Green Pea, might be a type of Luminous Blue Compact Galaxy which is undergoing very high rates of star formation.[1] Pea galaxies are so-named because of their small size and greenish appearance in the images taken by the Sloan Digital Sky Survey (SDSS).

Pea Galaxies were first discovered in 2007 by the volunteer users within the forum section of the online astronomy project Galaxy Zoo (GZ).[2]

My final entry for this first TED fellow session is about Shohini Ghose, as associate professor of physics, at Wilfrid Laurier University (Waterloo, Canada). She spoke beautifully and you** think you understand while the person’s speaking but aren’t all that sure afterwards. She was talking about chaos at the macro and at the quantum levels. The butterfly effect (a butterfly beats its wings in one part of the world and eventually that disturbance which is repeated is felt as a hurricane in another part of the world) can also occur at the quantum level. In fact, quantum entanglement is generated by chaos at the quantum scale. She was accompanied by a video representing chaos and movement at the quantum scale.

* ‘fellow’ changed to ‘fellows’ March 17, 2013 1606 hours PST
** ‘iyou’ changed to ‘you’ Nov. 19, 2014.

Capturing light in a bottle, a single-atom light switch, and superpositioning

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A Nov. 5, 2013 Vienna University of Technology press release (also available on EurekAlert) describes research that may make quantum optical switches possible,

With just a single atom, light can be switched between two fibre optic cables at the Vienna University of Technology. Such a switch enables quantum phenomena to be used for information and communication technology.

The press release goes on to describe a ‘light in a bottle’ technique which leads, the researchers hope, that they may have discovered how to create a quantum light switch,

Professor Arno Rauschenbeutel and his team at the Vienna University of Technology capture light in so-called “bottle resonators”. At the surface of these bulgy glass objects, light runs in circles. If such a resonator is brought into the vicinity of a glass fibre which is carrying light, the two systems couple and light can cross over from the glass fibre into the bottle resonator.

“When the circumference of the resonator matches the wavelength of the light, we can make one hundred percent of the light from the glass fibre go into the bottle resonator – and from there it can move on into a second glass fibre”, explains Arno Rauschenbeutel.

A Rubidium Atom as a Light Switch
This system, consisting of the incoming fibre, the resonator and the outgoing fibre, is extremely sensitive: “When we take a single Rubidium atom and bring it into contact with the resonator, the behaviour of the system can change dramatically”, says Rauschenbeutel. If the light is in resonance with the atom, it is even possible to keep all the light in the original glass fibre, and none of it transfers to the bottle resonator and the outgoing glass fibre. The atom thus acts as a switch which redirects light one or the other fibre.

Both Settings at Once: The Quantum Switch
In the next step, the scientists plan to make use of the fact that the Rubidium atom can occupy different quantum states, only one of which interacts with the resonator. If the atom occupies the non-interacting quantum state, the light behaves as if the atom was not there. Thus, depending on the quantum state of the atom, light is sent into either of the two glass fibres. This opens up the possibility to exploit some of the most remarkable properties of quantum mechanics: “In quantum physics, objects can occupy different states at the same time”, says Arno Rauschenbeutel. The atom can be prepared in such a way that it occupies both switch states at once. As a consequence, the states “light” and “no light” are simultaneously present in  each of the two glass fibre cables. [emphasis mine]

For the classical light switch at home, this would be plain impossible, but for a “quantum light switch”, occupying both states at once is not a problem. “It will be exciting to test, whether such superpositions are also possible with stronger light pulses. Somewhere we are bound to encounter a crossover between quantum physics and classical physics”, says Rauschenbeutel.

This light switch is a very powerful new tool for quantum information and quantum communication. “We are planning to deterministically create quantum entanglement between light and matter”, says Arno Rauschenbeutel. “For that, we will no longer need any exotic machinery which is only found in laboratories. Instead, we can now do it with conventional glass fibre cables which are available everywhere.”

Darrick Chang offers a good introduction (i.e., it’s challenging but you don’t need a physics degree to read it) and some analysis of this work in his Nov. 4, 2013 article for Physics (6, 121 (2013) DOI: 10.1103/Physics.6.121) titled: Viewpoint: A Single-Atom Optical Switch.

Quantum scientists over the past two decades have dreamt of realizing powerful new information technologies that exploit the laws of quantum mechanics in their operation. While many approaches are being pursued, a prevailing choice consists of using single atoms and particles of light—single photons—as the fundamental building blocks of these technologies [1]. In this paradigm, one envisions that single atoms naturally act as quantum processors that produce and interface with single photons, while the photons naturally act as wires to carry information between processors. Reporting in Physical Review Letters, researchers at the Vienna University of Technology, Austria, have taken an important step forward in this pursuit, by experimentally demonstrating a microphotonic optical switch that is regulated by just a single atom [2].

This article is open access.

For those willing to tackle a more challenging paper, here’s a link to and a citation for the Vienna University of Technology researchers’ paper,

Fiber-Optical Switch Controlled by a Single Atom by Danny O’Shea, Christian Junge, Jürgen Volz, and Arno Rauschenbeute. Phys. Rev. Lett. 111, 193601 (2013) [5 pages]

This work is behind a paywall.

Minutes after publishing: here’s an image that illustrates superpositioning in a quantum switch,

The Quantum Light Switch: It can occupy both possible states at the same time. Courtesy Vienna University of Technology

The Quantum Light Switch: It can occupy both possible states at the same time. Courtesy Vienna University of Technology

‘Entangling’ microscopic drum beats with electrical signals

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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.

Quantum teleportation from a Japan-Germany collaboration

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An Aug. 15, 2013 Johannes Gutenberg University Mainz press release (also on EurekAlert) has somewhat gobsmacked me with its talk of teleportation,

By means of the quantum-mechanical entanglement of spatially separated light fields, researchers in Tokyo and Mainz have managed to teleport photonic qubits with extreme reliability. This means that a decisive breakthrough has been achieved some 15 years after the first experiments in the field of optical teleportation. The success of the experiment conducted in Tokyo is attributable to the use of a hybrid technique in which two conceptually different and previously incompatible approaches were combined. “Discrete digital optical quantum information can now be transmitted continuously – at the touch of a button, if you will,” explained Professor Peter van Loock of Johannes Gutenberg University Mainz (JGU). As a theoretical physicist, van Loock advised the experimental physicists in the research team headed by Professor Akira Furusawa of the University of Tokyo on how they could most efficiently perform the teleportation experiment to ultimately verify the success of quantum teleportation.

The press release goes on to describe quantum teleportation,

Quantum teleportation involves the transfer of arbitrary quantum states from a sender, dubbed Alice, to a spatially distant receiver, named Bob. This requires that Alice and Bob initially share an entangled quantum state across the space in question, e.g., in the form of entangled photons. Quantum teleportation is of fundamental importance to the processing of quantum information (quantum computing) and quantum communication. Photons are especially valued as ideal information carriers for quantum communication since they can be used to transmit signals at the speed of light. A photon can represent a quantum bit or qubit analogous to a binary digit (bit) in standard classical information processing. Such photons are known as ‘flying quantum bits.

Before explaining the new technique, there’s an overview of previous efforts,

The first attempts to teleport single photons or light particles were made by the Austrian physicist Anton Zeilinger. Various other related experiments have been performed in the meantime. However, teleportation of photonic quantum bits using conventional methods proved to have its limitations because of experimental deficiencies and difficulties with fundamental principles.

What makes the experiment in Tokyo so different is the use of a hybrid technique. With its help, a completely deterministic and highly reliable quantum teleportation of photonic qubits has been achieved. The accuracy of the transfer was 79 to 82 percent for four different qubits. In addition, the qubits were teleported much more efficiently than in previous experiments, even at a low degree of entanglement.

The concept of entanglement was first formulated by Erwin Schrödinger and involves a situation in which two quantum systems, such as two light particles for example, are in a joint state, so that their behavior is mutually dependent to a greater extent than is normally (classically) possible. In the Tokyo experiment, continuous entanglement was achieved by means of entangling many photons with many other photons. This meant that the complete amplitudes and phases of two light fields were quantum correlated. Previous experiments only had a single photon entangled with another single photon – a less efficient solution. “The entanglement of photons functioned very well in the Tokyo experiment – practically at the press of a button, as soon as the laser was switched on,” said van Loock, Professor for Theory of Quantum Optics and Quantum Information at Mainz University. This continuous entanglement was accomplished with the aid of so-called ‘squeezed light’, which takes the form of an ellipse in the phase space of the light field. Once entanglement has been achieved, a third light field can be attached to the transmitter. From there, in principle, any state and any number of states can be transmitted to the receiver. “In our experiment, there were precisely four sufficiently representative test states that were transferred from Alice to Bob using entanglement. Thanks to continuous entanglement, it was possible to transmit the photonic qubits in a deterministic fashion to Bob, in other words, in each run,” added van Loock.

Earlier attempts to achieve optical teleportation were performed differently and, before now, the concepts used have proved to be incompatible. Although in theory it had already been assumed that the two different strategies, from the discrete and the continuous world, needed to be combined, it represents a technological breakthrough that this has actually now been experimentally demonstrated with the help of the hybrid technique. “The two separate worlds, the discrete and the continuous, are starting to converge,” concluded van Loock.

The researchers have provided an image illustrating quantum teleportation,

Deterministic quantum teleportation of a photonic quantum bit. Each qubit that flies from the left into the teleporter leaves the teleporter on the right with a loss of quality of only around 20 percent, a value not achievable without entanglement. Courtesy University of Tokyo

Deterministic quantum teleportation of a photonic quantum bit. Each qubit that flies from the left into the teleporter leaves the teleporter on the right with a loss of quality of only around 20 percent, a value not achievable without entanglement. Courtesy University of Tokyo

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

Deterministic quantum teleportation of photonic quantum bits by a hybrid technique by Shuntaro Takeda, Takahiro Mizuta, Maria Fuwa, Peter van Loock & Akira Furusawa. Nature 500, 315–318 (15 August 2013) doi:10.1038/nature12366 Published online 14 August 2013

This article  is behind a paywall although there is a preview capability (ReadCube Access) available.

Entangling diamonds

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Usually when you hear about entanglement, they’re talking about quantum particles or kittens. On Dec. 2, 2011, Science magazine published a paper by scientists who had entangled diamonds (that can be touched and held in human hands). From the Dec. 1, 2011 CBC (Canadian Broadcasting Corporation) news article by Emily Chung,

Quantum physics is known for bizarre phenomena that are very different from the behaviour we are familiar with through our interaction with objects on the human scale, which follow the laws of classical physics. For example, quantum “entanglement” connects two objects so that no matter how far away they are from one another, each object is affected by what happens to the other.

Now, scientists from the U.K., Canada and Singapore have managed to demonstrate entanglement in ordinary diamonds under conditions found in any ordinary room or laboratory.

Philip Ball in his Dec. 1, 2011 article for Nature magazine describes precisely what entanglement means when applied to the diamond crystals that were entangled,

A pair of diamond crystals has been linked by quantum entanglement. This means that a vibration in the crystals could not be meaningfully assigned to one or other of them: both crystals were simultaneously vibrating and not vibrating.

Quantum entanglement — interdependence of quantum states between particles not in physical contact — has been well established between quantum particles such as atoms at ultra-cold temperatures. But like most quantum effects, it doesn’t tend to survive either at room temperature or in objects large enough to see with the naked eye.

Entanglement, until now, has been demonstrated at very small scales due to an issue with coherence and under extreme conditions. Entangled objects are coherent with each other but other objects such as atoms can cause the entangled objects to lose their coherence and their entangled state. In order to entangle the diamonds, the scientists had to find a way of dealing with the loss of coherence as the objects are scaled up and they were able to achieve this at room temperature. From the Emily Chung article,

Walmsley [Ian Walmsley, professor of experimental physics at the University of Oxford] said it’s easier to maintain coherence in smaller objects because they can be isolated practically from disturbances. Things are trickier in larger systems that contain lots of interacting, moving parts.

Two things helped the researchers get around this in their experiment, Sussman [Ben Sussman, a quantum physicist at the National Research Council of Canada and adjunct professor at the University of Ottawa] said:

  • The hardness of the diamonds meant it was more resistant to disturbances that could destroy the coherence.
  • The extreme speed of the experiment — the researchers used laser pulses just 60 femtoseconds long, about 6/100,000ths of a nanosecond (a nanosecond is a billionth of a second) — meant there was no time for disturbances to destroy the quantum effects.

Laser pulses were used to put the two diamonds into a state where they were entangled with one another through a shared vibration known as a phonon. By measuring particles of light called photons subsequently scattered from the diamonds, the researchers confirmed that the states of the two diamonds were linked with each other — evidence that they were entangled.

If you are interested in the team’s research and can get past Science magazine’s paywall, here’s the citation,

“Entangling Macroscopic Diamonds at Room Temperature,” by K.C. Lee; M.R. Sprague; J. Nunn; N.K. Langford; X.-M. Jin; T. Champion; P. Michelberger; K.F. Reim; D. England; D. Jaksch; I.A. Walmsley at University of Oxford in Oxford, UK; B.J. Sussman at National Research Council of Canada in Ottawa, ON, Canada; X.-M. Jin; D. Jaksch at National University of Singapore in Singapore. Science 2 December 2011: Vol. 334 no. 6060 pp. 1253-1256 DOI: 10.1126/science.1211914

All of the media reports I’ve seen to date focus on the UK and Canadian researchers and I cannot find anything about the contribution of the researcher based in Singapore.

I do wish I could read more languages as I’d be more likely to find information about work which is not necessarily going to be covered in English language media.