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Physics Frontier Center

About the PFC @ JQI

The Physics Frontier Center is devoted to leading-edge experimental and theoretical investigation of ways to control and process quantum coherence and entanglement: the physics of quantum information. It is funded through a cooperative agreement with the National Science Foundation (NSF) and operated within the Joint Quantum Institute (JQI), a partnership between the University of Maryland (UMD) and the National Institute of Standards and Technology (NIST), with additional support from the Laboratory for Physical Sciences.

Latest News

  • Eliot Fenton recognized as a Maryland ‘Undergraduate Researcher of the Year’
  • May 8, 2018

Eliot Fenton, UMD physics major, was among those recognized as a 2018 Maryland ‘Undergraduate Researcher of the Year.’ This award is eligible for exemplary seniors who have been nominated by their faculty advisors.  Fenton earned this award for his wide-ranging experimental physics research accomplishments.

From 2015-2017 Fenton worked on optical nanofibers with JQI Fellow and UMD Physics Professor Luis Orozco. Recently, Fenton along with fellow undergraduate researcher Adnan Khan (now a graduate student at University of Washington), together with colleagues, published a study of how light interacts with an optical nanofiber’s mechanical movements. Last year, Fenton co-authored a paper that detailed precise measurements of an optical nanofiber.

Eliot Fenton (right) with research advisor Luis Orozco (center) and former UMD graduate student Pablo Solano (left), recipient of the Caramello Distinguished Dissertation Prize. (Photo courtesy of L. Orozco)

In 2017 he began doing research with JQI Fellow and NIST scientist Ian Spielman and his team. In this group, Fenton has been working on the construction of a new ultracold atomic physics experiment in the Physical Sciences Complex.

In addition to UMD research activities, Fenton completed summer research internships at both the Niels Bohr Institute in Denmark and CERN. Fenton, who will graduate in May 2018, is planning to attend graduate school at Harvard University, where he will study ultracold molecules with Assistant Professor of Chemistry and Chemical Biology Kang-Kuen Ni.

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  • JQI alumnus Pablo Solano awarded dissertation prize
  • April 23, 2018

Pablo Solano, a recent graduate student with JQI Fellow and UMD physics professor Luis Orozco, has been awarded the Charles A. Caramello Distinguished Dissertation Prize. According to the official award description, the prize recognizes “original work that makes an unusually significant contribution to its discipline.” The prize is given in four broad disciplinary areas and comes with an honorarium.

Solano received the prize in the area of Mathematics, Physical Sciences, and Engineering for his dissertation titled “Quantum Optics in Optical Nanofibers”. His research focused on studying the properties of light as it propagates through optical nanofibers, and how such a system enables special atom-light interactions. His thesis work was nominated by the College of Computer, Mathematical and Natural Sciences and selected by a multi-disciplinary campus committee. Solano will be honored at the UMD Graduate School’s Ninth Annual Fellowship and Award Celebration.

Solano is currently a postdoctoral associate at the Research Laboratory for Electronics and the Physics department at MIT. He is currently working on cavity-QED experiments in the strong coupling regime using laser cooled cesium atoms trapped at the center of a high-finesse Fabry-Perot cavity.

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  • Atoms may hum a tune from grand cosmic symphony
  • An expanding cloud of atoms could offer insight into unanswered cosmological questions.
  • April 19, 2018 Activity 1

Researchers playing with a cloud of ultracold atoms uncovered behavior that bears a striking resemblance to the universe in microcosm. Their work, which forges new connections between atomic physics and the sudden expansion of the early universe, was published April 19 in Physical Review X and featured in Physics.

"From the atomic physics perspective, the experiment is beautifully described by existing theory," says Stephen Eckel, an atomic physicist at the National Institute of Standards and Technology (NIST) and the lead author of the new paper. "But even more striking is how that theory connects with cosmology."

In several sets of experiments, Eckel and his colleagues rapidly expanded the size of a doughnut-shaped cloud of atoms, taking snapshots during the process. The growth happens so fast that the cloud is left humming, and a related hum may have appeared on cosmic scales during the rapid expansion of the early universe—an epoch that cosmologists refer to as the period of inflation.

The work brought together experts in atomic physics and gravity, and the authors say it is a testament to the versatility of the Bose-Einstein condensate (BEC)—an ultracold cloud of atoms that can be described as a single quantum object—as a platform for testing ideas from other areas of physics.

"Maybe this will one day inform future models of cosmology," Eckel says. "Or vice versa. Maybe there will be a model of cosmology that’s difficult to solve but that you could simulate using a cold atomic gas."

It’s not the first time that researchers have connected BECs and cosmology. Prior studies mimicked black holes and searched for analogs of the radiation predicted to pour forth from their shadowy boundaries. The new experiments focus instead on the BEC’s response to a rapid expansion, a process that suggests several analogies to what may have happened during the period of inflation.

The first and most direct analogy involves the way that waves travel through an expanding medium. Such a situation doesn’t arise often in physics, but it happened during inflation on a grand scale. During that expansion, space itself stretched any waves to much larger sizes and stole energy from them through a process known as Hubble friction.

In one set of experiments, researchers spotted analogous features in their cloud of atoms. They imprinted a sound wave onto their cloud—alternating regions of more atoms and fewer atoms around the ring, like a wave in the early universe—and watched it disperse during expansion. Unsurprisingly, the sound wave stretched out, but its amplitude also decreased. The math revealed that this damping looked just like Hubble friction, and the behavior was captured well by calculations and numerical simulations.

"It's like we're hitting the BEC with a hammer," says Gretchen Campbell, the NIST co-director of the Joint Quantum Institute (JQI) and a coauthor of the paper, "and it’s sort of shocking to me that these simulations so nicely replicate what's going on."

In a second set of experiments, the team uncovered another, more speculative analogy. For these tests they left the BEC free of any sound waves but provoked the same expansion, watching the BEC slosh back and forth until it relaxed.

In a way, that relaxation also resembled inflation. Some of the energy that drove the expansion of the universe ultimately ended up creating all of the matter and light around us. And although there are many theories for how this happened, cosmologists aren’t exactly sure how that leftover energy got converted into all the stuff we see today.

In the BEC, the energy of the expansion was quickly transferred to things like sound waves traveling around the ring. Some early guesses for why this was happening looked promising, but they fell short of predicting the energy transfer accurately. So the team turned to numerical simulations that could capture a more complete picture of the physics.

What emerged was a complicated account of the energy conversion: After the expansion stopped, atoms at the outer edge of the ring hit their new, expanded boundary and got reflected back toward the center of the cloud. There, they interfered with atoms still traveling outward, creating a zone in the middle where almost no atoms could live. Atoms on either side of this inhospitable area had mismatched quantum properties, like two neighboring clocks that are out of sync.

The situation was highly unstable and eventually collapsed, leading to the creation of vortices throughout the cloud. These vortices, or little quantum whirlpools, would break apart and generate sound waves that ran around the ring, like the particles and radiation left over after inflation. Some vortices even escaped from the edge of the BEC, creating an imbalance that left the cloud rotating.

Unlike the analogy to Hubble friction, the complicated story of how sloshing atoms can create dozens of quantum whirlpools may bear no resemblance to what goes on during and after inflation. But Ted Jacobson, a coauthor of the new paper and a physics professor at the University of Maryland specializing in black holes, says that his interaction with atomic physicists yielded benefits outside these technical results.

"What I learned from them, and from thinking so much about an experiment like that, are new ways to think about the cosmology problem," Jacobson says. "And they learned to think about aspects of the BEC that they would never have thought about before. Whether those are useful or important remains to be seen, but it was certainly stimulating."

Eckel echoes the same thought. "Ted got me to think about the processes in BECs differently," he says, "and any time you approach a problem and you can see it from a different perspective, it gives you a better chance of actually solving that problem."

Future experiments may study the complicated transfer of energy during expansion more closely, or even search for further cosmological analogies. "The nice thing is that from these results, we now know how to design experiments in the future to target the different effects that we hope to see," Campbell says. "And as theorists come up with models, it does give us a testbed where we could actually study those models and see what happens."

The new paper included contributions from two coauthors not mentioned in the text: Avinash Kumar, a graduate student at JQI; and Ian Spielman, a JQI Fellow and NIST physicist.

Story by Chris Cesare

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  • Latest nanowire experiment boosts confidence in Majorana sighting
  • New test matches theory and offers the best evidence yet for the oddball particles.
  • March 28, 2018 Activity 1

In the latest experiment of its kind, researchers have captured the most compelling evidence to date that unusual particles lurk inside a special kind of superconductor. The result, which confirms theoretical predictions first made nearly a decade ago at the Joint Quantum Institute (JQI) and the University of Maryland (UMD), will be published in the April 5 issue of Nature

The stowaways, dubbed Majorana quasiparticles, are different from ordinary matter like electrons or quarks—the stuff that makes up the elements of the periodic table. Unlike those particles, which as far as physicists know can’t be broken down into more basic pieces, Majorana quasiparticles arise from coordinated patterns of many atoms and electrons and only appear under special conditions. They are endowed with unique features that may allow them to form the backbone of one type of quantum computer, and researchers have been chasing after them for years.

The latest result is the most tantalizing yet for Majorana hunters, confirming many theoretical predictions and laying the groundwork for more refined experiments in the future. In the new work, researchers measured the electrical current passing through an ultra-thin semiconductor connected to a strip of superconducting aluminum—a recipe that transforms the whole combination into a special kind of superconductor.

Experiments of this type expose the nanowire to a strong magnet, which unlocks an extra way for electrons in the wire to organize themselves at low temperatures. With this additional arrangement the wire is predicted to host a Majorana quasiparticle, and experimenters can look for its presence by carefully measuring the wire’s electrical response. 

The new experiment was conducted by researchers from QuTech at the Technical University of Delft in the Netherlands and Microsoft Research, with samples of the hybrid material prepared at the University of California, Santa Barbara and Eindhoven University of Technology in the Netherlands. Experimenters compared their results to theoretical calculations by JQI Fellow Sankar Das Sarma and JQI graduate student Chun-Xiao Liu.

The same group at Delft saw hints of a Majorana in 2012, but the measured electrical effect wasn’t as big as theory had predicted. Now the full effect has been observed, and it persists even when experimenters jiggle the strength of magnetic or electric fields—a robustness that provides even stronger evidence that the experiment has captured a Majorana, as predicted in careful theoretical simulations by Liu.

"We have come a long way from the theoretical recipe in 2010 for how to create Majorana particles in semiconductor-superconductor hybrid systems," says Das Sarma, a coauthor of the paper who is also the director of the Condensed Matter Theory Center at UMD. "But there is still some way to go before we can declare total victory in our search for these strange particles."

The success comes after years of refinements in the way that researchers assemble the nanowires, leading to cleaner contact between the semiconductor wire and the aluminum strip. During the same time, theorists have gained insight into the possible experimental signatures of Majoranas—work that was pioneered by Das Sarma and several collaborators at UMD.

Theory meets experiment

The quest to find Majorana quasiparticles in thin quantum wires began in 2001, spurred by Alexei Kitaev, then a physicist then at Microsoft Research. Kitaev, who is now at the California Institute of Technology in Pasadena, concocted a relatively simple but unrealistic system that could theoretically harbor a Majorana. But this imaginary wire required a specific kind of superconductivity not available off-the-shelf from nature, and others soon began looking for ways to imitate Kitaev’s contraption by mixing and matching available materials.

One challenge was figuring out how to get superconductors, which usually go about their business with an even number of electrons—two, four, six, etc.—to also allow an odd number of electrons, a situation that is normally unstable and requires extra energy to maintain. The odd number is necessary because Majorana quasiparticles are unabashed oddballs: They only show up in the coordinated behavior of an odd number of electrons. 

In 2010, almost a decade after Kitaev’s original paper, Das Sarma, JQI Fellow Jay Deep Sau and JQI postdoctoral researcher Roman Lutchyn, along with a second group of researchers, struck upon a method to create these special superconductors, and it has driven the experimental search ever since. They suggested combining a certain kind of semiconductor with an ordinary superconductor and measuring the current through the whole thing. They predicted that the combination of the two materials, along with a strong magnetic field, would unlock the Majorana arrangement and yield Kitaev’s special material.

They also predicted that a Majorana could reveal itself in the way current flows through such a nanowire. If you connect an ordinary semiconductor to a metal wire and a battery, electrons usually have some chance of hopping off the wire onto the semiconductor and some chance of being rebuffed—the details depend on the electrons and the makeup of the material. But if you instead use one of Kitaev’s nanowires, something completely different happens. The electron always gets perfectly reflected back into the wire, but it’s no longer an electron. It becomes what scientists call a hole—basically a spot in the metal that’s missing an electron—and it carries a positive charge back in the opposite direction.

Physics demands that the current across the interface be conserved, which means that two electrons must end up in the superconductor to balance out the positive charge heading in the other direction. The strange thing is that this process, which physicists call perfect Andreev reflection, happens even when electrons in the metal receive no push toward the boundary—that is, even when they aren’t hooked up to a battery of sorts. This is related to the fact that a Majorana is its own antiparticle, meaning that it doesn’t cost any energy to create a pair of Majoranas in the nanowire. The Majorana arrangement gives the two electrons some extra room to maneuver and allows them to traverse the nanowire as a quantized pair—that is, exactly two at a time. 

"It is the existence of Majoranas that gives rise to this quantized differential conductance," says Liu, who ran numerical simulations to predict the results of the experiments on UMD’s Deepthought2 supercomputer cluster. "And such a quantization should even be robust to small changes in experimental parameters, as the real experiment shows."

Scientists refer to this style of experiment as tunneling spectroscopy because electrons are taking a quantum route through the nanowire to the other side. It has been the focus of recent efforts to capture Majoranas, but there are other tests that could more directly reveal the exotic properties of the particles—tests that would fully confirm that the Majoranas are really there. 

"This experiment is a big step forward in our search for these exotic and elusive Majorana particles, showing the great advance made in the materials improvement over the last five years," Das Sarma says. "I am convinced that these strange particles exist in these nanowires, but only a non-local measurement establishing the underlying physics can make the evidence definitive."

By Chris Cesare

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  • Two-toned light pattern creates steep quantum walls for atoms
  • A new landscape promises to bring ultracold atomic neighbors closer than ever before
  • March 13, 2018

Exotic physics can happen when quantum particles come together and talk to each other. Understanding such processes is challenging for scientists, because the particle interactions can be hard to glimpse and even harder to control. Moreover, modern computer simulations struggle to make sense of all the intricate dynamics going on in a large group of particles. Luckily, atoms cooled to near zero temperatures can provide insight into this problem.

Lasers can make cold atoms mimic the physics seen in other systems—an approach that is familiar terrain for atomic physicists. They regularly use intersecting laser beams to capture atoms in a landscape of rolling hills and valleys called an optical lattice. Atoms, when cooled, don’t have enough energy to walk up the hills, and they get stuck in the valleys. In this environment, the atoms behave similarly to the electrons in the crystal structure of many solids, so this approach provides a straightforward way to learn about interactions inside real materials.

But the conventional way to make optical lattices has some limitations. The wavelength of the laser light determines the location of the hills and valleys, and so the distance between neighboring valleys—and with that the spacing between atoms—can only be shrunk to half of the light’s wavelength. Bringing atoms closer than this limit could activate much stronger interactions between them and reveal effects that otherwise remain in the dark.

Now, a team of scientists from the Joint Quantum Institute (JQI), in collaboration* with researchers from the Institute for Quantum Optics and Quantum Information in Innsbruck, Austria, has circumvented the wavelength limit by leveraging the atoms’ inherent quantum features, which should allow atomic lattice neighbors to get closer than ever before. The new technique manages to squeeze the gentle lattice hills into steep walls separated by only one-fiftieth of the laser’s wavelength—25 times narrower than possible with conventional methods. The work, which is based on two prior theoretical proposals**, was recently published in Physical Review Letters.

In most optical lattices, atoms are arranged by repeating smooth dips in the intensity of laser light—a mechanism that also works with non-quantum objects like bacteria or even glass beads. But this ignores many inherent quantum characteristics of the atoms. Unlike glass beads, atoms, prompted by laser light of certain colors, can internally switch between different quantum versions of themselves, called states. The team exploits this property to build lattices that effectively replace the rolling hills with spiky features.

“The trick is that we don’t rely on the light’s intensity by itself,” explains Yang Wang, a postdoctoral researcher at the JQI and the lead author of the paper. “Instead, we use light as a tool to facilitate a quantum mechanical effect. And that creates the new kind of landscape for the atoms.”

To create this lattice, the researchers ensnare the atoms in a two-toned light pattern. Each color is chosen so that it can change an atom’s internal state on its own, but when the two colors overlap, the more intense color at each spot takes charge and decides which internal state the atom lands in. But this pattern is not smooth—there are vast valleys where the atom prefers one state, interrupted by thin strips where it should switch. The rules of quantum mechanics dictate that every time an atom changes its state, the atom must pay a price in the form of energy, just like climbing a hill. While a smooth transition may appear as a Sunday stroll to the atom, large changes over shorter distances quickly evolve into an increasingly steep hike. In the experiment, the thin strips inside the light pattern are so narrow, that they look like insurmountable walls to the atom, so it avoids them and gets stuck in between.

These sharp walls are an important first step in the quest to bring atoms even closer. The new technique still provides plenty of room for atoms to travel within the wide, flat plains, but researchers plan to reduce this freedom by adding more barriers. “As we take steps to confine the atoms further and further, quantum effects between the atoms should become increasingly important,” says Trey Porto, a JQI Fellow and an author of the paper. “This has a practical side effect, because it also increases the temperature that we need to be at to see weird quantum behavior. Cooling is quite difficult, so this would make the physics that we’re after more easily attainable.”

The research team says that this tool may also be useful for future quantum chemistry experiments, allowing scientists to bring atoms close enough to engage in a small-scale, highly-controlled reaction.

Written by Nina Beier
 
* The research was also done in collaboration with the Joint Center for Quantum Information and Computer Science at the University of Maryland, the Jagiellonian University in Kraków, Poland, and the University of Innsbruck in Austria.
 
** The work was based on the following proposals: Phys. Rev. Lett. 117, 233001 (2016) and Phys. Rev. A 94, 063422 (2016)
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Brief Reports

A team of PFC-funded scientists from JQI has leveraged atoms’ inherent quantum features to allow neighbors in an atomic lattice to get closer than ever before. The new technique manages to squeeze the ordinary gentle hills of an... Read more

A collaboration of PFC-funded researchers from JQI has created a photonic chip that both generates single photons, and steers them around certain kinds of obstacles.

The chip starts with a photonic crystal, which is an established, versatile technology used to create roadways for light.... Read more

In the latest experiment of its kind, researchers have captured the most compelling evidence to date that unusual particles lurk inside a special kind of superconductor.

The stowaways, dubbed Majorana quasiparticles, are different from ordinary matter like electrons or quarks—the stuff... Read more

In several sets of experiments, PFC-funded researchers at JQI rapidly expanded the size of a doughnut-shaped cloud of atoms, taking snapshots during the process. The growth happens so fast that the cloud is left humming, and a related hum may have appeared on cosmic scales during the rapid... Read more

Solitons — solitary waves that behave more like discrete particles than waves — occur in diverse physical systems, from water in a canal to light waves in optical-fiber telecommunications. They can also exist in Bose-Einstein condensates, manifesting as stable density waves.

In a pristine... Read more

Only in quantum physics can traffic be standing still and moving at the same time.

A new paper from scientists at the National Institute of Standards and Technology (NIST) and the University of Maryland suggests that intentionally creating a traffic jam out of a ring of several thousand... Read more

Optical fibers are the backbone of modern communications, shuttling information from A to B through thin glass filaments as pulses of light. They are used extensively in telecommunications, allowing information to travel at near the speed of light virtually without loss. 

These days,... Read more

In 2012, Nobel-prize winning physicist Frank Wilczek, a professor at the Massachusetts Institute of Technology, proposed something that sounds pretty strange. It might be possible, Wilczek argued, to create crystals that are arranged in time instead of space. The suggestion prompted years of... Read more

Quantum computers promise speedy solutions to some difficult problems, but building large-scale, general-purpose quantum devices is a problem fraught with technical challenges.

In a paper published as the cover story in Nature on August 4, 2016, PFC-funded researchers introduced the first... Read more

Physical systems that retain no memory of their initial conditions are said to have thermalized, since it is often—but not always—an exchange of heat and energy with another system that causes the memory loss. The opposite case is localization, where information about the initial arrangement... Read more

Pumps have been around for millennia, but recently physicists have sought to build a different kind of pump—one that could use the rules of quantum mechanics to pump atoms or charges in a quantized way. PFC-supported researchers have created the first pump based on the geometry of quantum... Read more

Magnetic fields arise from the microscopic behavior of atoms and their electrons. In permanent magnets, neighboring atoms align and lock into place to create inseparable north and south poles. For other materials, magnetism can be induced by a field strong enough to coax atoms into alignment.... Read more

Rydberg atoms are a popular choice for quantum device proposals because they interact strongly with each other and their individual and collective behavior is easy to manipulate. While experimenting with rubidium, one of the most popular Rydberg systems, PFC-supported researchers discovered an... Read more

In the fractional quantum Hall (FQH) effect, the collective action of electrons in a material form particle-like “quasiparticles” that can appear to possess fractional charge, such as 1/3. In quantum Hall systems, these quasiparticles can become trapped around specially tailored defects, forming... Read more

Ultracold atomic systems can be used to model condensed-matter physics, providing precise control of system variables often not achievable in real materials. This involves inducing charge-neutral particles to behave as if they were charged particles in a magnetic field. To this end, PFC-... Read more

Particles can be classified as bosons or fermions. A defining characteristic of a boson is its ability to pile into a single quantum state with other bosons. Fermions are not allowed to do this. One broad impact of fermionic anti-social behavior is that it allows for carbon-based life forms,... Read more

PFC-supported researchers have used trapped atomic ions to construct a system that could potentially support a type of symmetry-protected quantum state. For this research they used a three-state system, called a qutrit, to demonstrate a proof-of-principle experiment for performing quantum... Read more

Optical nanofibers are optical fibers that have a diameter smaller than the wavelength of the guided light. Here, all of the light field cannot fit inside of the fiber, yielding a significant enhancement in the evanescent fields outside of the core. This allows the light to trap atoms (or other... Read more

If you’re designing a new computer, you want it to solve problems as fast as possible. Just how fast is possible is an open question when it comes to quantum computers, but PFC supported physicists have developed a new mathematical proof that reveals a much tighter limit on how fast quantum... Read more

The 2014 chemistry Nobel Prize recognized important microscopy research that enabled greatly improved spatial resolution. This innovation, resulting in nanometer resolution, was made possible by making the source (the emitter) of the illumination  quite small and by moving it quite close to the... Read more

Strongly correlated electronic systems, like superconductors, display remarkable electronic and magnetic properties. Creating analogous states in Bose gases is an excellent way to model the dynamics of these systems, offering a level of control often not possible in solid state systems.

... Read more

In certain situations, a collection of atoms can transition to a superfluid state, flouting the normal rules of liquid behavior. Harnessing this effect is of particular interest in the field of atomtronics, since superfluid atom circuits can recreate the functionality of superconductor circuits... Read more

Atom-optical lattice systems offer a clean, well-controlled way to study the manipulation and movement of spins because researchers can create particle configurations analogous to crystalline order in materials. PFC supported theorists have been developing a model for what happens when ultracold... Read more

Topological transport of light is the photonic analog of topological electron flow in certain semiconductors. In the electron case, the current flows around the edge of the material but not through the bulk. It is “topological” in that even if electrons encounter impurities in the material the... Read more

Atomtronics is an emerging technology whereby physicists use ensembles of atoms to build analogs to electronic circuit elements. Using a superfluid atomtronic circuit, PFC supported physicists have demonstrated a tool that is critical to electronics: hysteresis. This is the first time that... Read more

Can scientists generate any color of light? The answer is not really, but the invention of the laser in 1960 opened new doors for this endeavor. An early experiment injected high-power laser light through quartz and out popped a different color. This sparked the field of nonlinear optics and... Read more

Topology -- the understanding of how things are connected -- remains abstract, even with the popular example of doughnuts and coffee cups. This concept, esoteric as it appears, is also neat because it is the basis for creating ultrastable quantum "playgrounds."  In topological systems, certain... Read more

The photodetectors in Alan Migdall’s lab often see no light at all, and that’s a good thing since he and his JQI colleagues perform physics experiments that require very little light, the better to study subtle quantum effects. The bursts of light they observe typically consist of only one or... Read more

A JQI/PFC experiment establishes a new record for symmetric single-mode, single-photon, heralding efficiency for a pair of entangled photons produced during parametric downconversion. About 84% of the time they observe photon A in one detector they also observe photon B just where it should be... Read more

PFC researchers explored how to frustrate a quantum magnet comprised of sixteen atomic ions – to date the largest ensemble of qubits to perform a simulation of quantum matter.

Physicists engineer a quantum magnet using lasers and ion ... Read more

All computers, even the future quantum versions, use logic operations or “gates,” which are the fundamental building blocks of computational processes. PFC scientists have performed an ultrafast logic gate on a photon, using a semiconductor quantum dot.

Quantum dots are an attractive... Read more

Last year Paul Lett and his JQI colleagues reported the ability to store a sequence of images (two letters of the alphabet) which were separated in time but overlapping in space within the volume of a gas-filled memory cell. This is random access in time. In a new experiment, by contrast, parts... Read more

The blackbody radiation shift imposed by atom traps on the energy level of the enclosed ultracold atoms will soon impose limits on the accuracy of the best atomic clocks. Although only important at a precision level of a part in 1015, accurate knowledge of this shift is more pertinent now that... Read more

Physicists at the Joint Quantum Institute (JQI) and the University of Maryland show, for the first time, that qubits can successfully exist in a topological superconductor material even in the presence of impurities in the material and strong interactions among participating electrons, courtesy... Read more

Magnetic monopoles weren’t supposed to exist. If you try to saw a bar magnet in half, all you succeed in getting are two magnets, each with a south and north pole. In recent years, however, the existence of monopole quasiparticles consisting of collective excitations among many atoms has been... Read more

A PFC-supported experiment conducted at the Joint Quantum Institute examines the role of disorder in maintaining quantum coherence. It does this by introducing disorder into a Bose-Einstein condensate of rubidium atoms held in an optical lattice to simulate the role is impurity disorder in high... Read more

PFC-supported scientists have stored not one but two letters of the alphabet in a tiny cell filled with rubidium atoms which are tailored to absorb and later re-emit messages on demand. This is the first time two images have simultaneously been reliably stored in a non-solid medium and then... Read more

PFC-supported experimentalists have developed a novel form of lattice for atoms. This lattice does not arise from a spatially varying light intensity pattern, as is the case for traditional optical lattices.  Instead, laser radiation generates an effective magnetic field that changes the... Read more

An optical switch developed at the Joint Quantum Institute (JQI) spurs the prospective integration of photonics and electronics. The JQI switch can steer a beam of light from one direction to another in only 120 ps using only about 90 attojoules of input power. At the wavelength used, in the... Read more

New PFC-supported work shows how a simple “joystick” consisting of an adjustable magnetic field can create several new phases of atomtronic matter, many of them never seen before. The field is used to tune the interaction---giving the researcher force on demand, causing the atoms to assume... Read more

PFC research at the Joint Quantum Institute (JQI) has for the first time engineered and detected the presence of effective high angular momentum collisions between atoms at temperatures close to absolute zero. Previous experiments with ultracold atoms featured essentially head-on collisions. The... Read more

Electrons carry information over tiny distances in computer circuitry. Photons are commonly used to carry information over kilometer distances. Scientists are currently developing micron-scale optical devices to replace and/or be compatible with electron-based circuit elements.

Diodes... Read more

Ultracold atomic gases trapped by laser light have become a playground for exploring quantum matter and even uncovering new phenomena not yet seen in nature.

PFC researchers at JQI have shown that this kind of optical lattice system can exhibit a never-before-seen quantum state called a... Read more

If quantum computers are ever to be realized, they likely will be made of different components sharing information with one another, just as the memory and logic circuits in today's computers do. Yet, it remains unclear how the quantum states in these different systems interact.

A team of... Read more

PFC-supported research at JQI has uncovered evidence for a long-sought-after quantum state of matter, a spin liquid. You can’t pour a spin liquid into a glass.  It’s not a material at all, at least not a material you can touch. It is more like a kind of magnetic disorder within an ordered array... Read more

Quantum spin models are powerful because they can describe many types of physical phenomena such as phase transitions in magnets. Simulations of these models can provide insights when the actual system of interest is difficult to understand theoretically or challenging to experimentally probe.... Read more

Researchers in a collaboration between the PFC at JQI and CalTech have shown that it may be possible to take a conventional semiconductor and endow it with topological properties without subjecting the material to extreme environmental conditions or fundamentally changing its solid state... Read more

In atomtronics scientists construct circuit elements using ultra-cold atomic gases where the atoms take the role of electrons. PFC scientists have developed an experiment that not only generates... Read more

PFC experimentalists in the Trapped Ion Quantum Information group have performed a gate that flips the state of a single atomic qubit in less than 50 picoseconds. The time to perform this same operation with continuous wave (CW) ... Read more

PFC-supported researchers, lead by Ian Spielman, recently demonstrated for the first time spin-orbit coupling in Bose-Einstein condensates (BECs), where the neutral atoms exhibited properties similar to electrons in material systems.

The scientists engineered a laser-atom interaction... Read more

“Frustrated" ensembles of interacting components – that is, those which cannot settle into a state that minimizes each interaction – may be the key to understanding a host of puzzling phenomena that affect systems from neural networks and social structures to protein folding and magnetism.... Read more

Random number sequences are needed for data encryption and other critical uses – yet truly random numbers are nearly impossible to come by. All classical processes such as coin flips are, in principle, predictable. But one thing that absolutely cannot be predicted is the value resulting... Read more

For the first time, scientists have employed a powerful technique of laser physics – the “optical frequency comb” – to entangle two trapped atoms. This form of control is a promising candidate for use as a logic gate for quantum computing and information-processing, and offers substantial... Read more

PFC-supported scientists have devised a new method that could be used to generate multiple pairs of “indistinguishable” photons – near-identical individual quanta of light – by fine-tuning the output from two separate quantum dots. Manipulating single photons will play a role in any eventual... Read more

Topological quantum computing (TQC), in which the data are protected against decoherence because they are stored and manipulated as shapes, is a highly desirable goal in quantum information science. Unfortunately, the only physical system in which anything approaching topological protection has... Read more

Physicists supported by the PFC at the Joint Quantum Institute have developed a new source of “entangled” photons – fundamental units of light whose properties are so intertwined that if the condition of one is measured, the condition of the other is instantaneously known, even if the photons... Read more

The behavior of quantum dots – nanometer-scale semiconductor formations that have many of the same quantized properties as atoms when interacting with light – is a subject of intense interest in condensed-matter physics. Now researchers supported by the Joint Quantum Institute’s Physics Frontier... Read more

PFC-supported scientists have demonstrated a new way to control quantum interactions that makes it possible to fine-tune the way in which the spin properties of trapped atoms couple to, and are "entangled" with, those of their neighbors -- a development with potentially important applications in... Read more

Quantum entanglement, a condition in which the states of two different objects become so inextricably linked that neither can be described separately, is an essential element of any future quantum computer. Scientists have succeeded in entangling many sorts of entities, typically identical atom... Read more

The simplest form of Bose-Einstein condensation occurs when a number of bosonic atoms (those with integer net spin) coalesce into the lowest possible energy state. Such condensates exhibit macrosopic quantum interference, persistent vortex currents and other manifestations of superfluidity. ... Read more

 

PFC-supported physicists have created and demonstrated a remote “quantum gate” – a key component for long-range quantum information transfer and an essential... Read more

Ian Spielman of the Joint Quantum Institute proposed a novel experimental protocol whereby neutral atoms in a Bose-Einstein condensate would behave like charged particles in a magnetic field. Physicists can use such an arrangement to create precisely tunable models to study the dynamics of... Read more

Twenty years ago, Purdue University scientists proposed a highly promising design for a “spin effect” transistor – the Datta-Das transistor, or DDT. To date, however, no one has been able to build a working model. Now JQI researchers have devised a potential solution to the problem: creating a... Read more

Neutral atoms, having no net electric charge, usually don't act very dramatically around a magnetic field. But by “dressing up” a Bose-Einstein condensate of rubidium atoms – applying two beams of laser light, thus giving the atoms an effective directional tendency, or vector potential -- PFC... Read more

Topological insulators form in certain materials that, in bulk, have the distinctive physical signature of insulators: That is, the permitted energy levels (or “bands”) in their component atomic structures are characterized by a full valence band and an empty conduction band, with a substantial... Read more

Two ions are placed in separate, unconnected traps 1 meter apart. A “message” is imprinted on Ion A via a microwave pulse. Then the ions are excited into a state in which they emit one photon each. Either photon can be one of two slightly different wavelengths. Those photons travel through... Read more

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About the PFC @ JQI

The Physics Frontier Center is devoted to leading-edge experimental and theoretical investigation of ways to control and process quantum coherence and entanglement: the physics of quantum information. It is funded through a cooperative agreement with the National Science Foundation (NSF) and operated within the Joint Quantum Institute (JQI), a partnership between the University of Maryland (UMD) and the National Institute of Standards and Technology (NIST), with additional support from the Laboratory for Physical Sciences.

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PFC General Info: pfc-info@umd.edu   Academic and Research Info: Luis Orozco | Atlantic Building 2203 | (301) 405-9740 | lorozco@umd.edu