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.

August 19, 2020 | PFC | Research News

Quantum Computers Do the (Instantaneous) Twist

Regardless of what makes up the innards of a quantum computer, its speedy calculations all boil down to sequences of simple instructions applied to qubits—the basic units of information inside a quantum computer.

July 13, 2020 | Research News |PFC

New Quantum Information Speed Limits Depend on the Task at Hand

Unlike speed limits on the highway, most speed limits in physics cannot be disobeyed. For example, no matter how little you care about getting a ticket, you can never go faster than the speed of light. Similarly stringent limits exist for information, too. The speed of light is still the ultimate speed limit, but depending on how information is stored and transmitted, there can be slower limits in practice.

April 15, 2020 | Research News |PFC

Peeking into a World of Spin-3/2 Materials

Researchers have been pushing the frontiers of the quantum world for over a century. And time after time, spin has been a rich source of new physics.

April 15, 2020 | Research News |PFC

New Protocol Helps Classify Topological Matter

Topological materials have captured the interest of many scientists and may provide the basis for a new era in materials development. On April 10, 2020 in the journal Science Advances, physicists working with Andreas Elben, Jinlong Yu, Peter Zoller and Benoit Vermersch, including JQI Fellow Mohammad Hafezi and former JQI postdoctoral researcher Guanyu Zhu (currently a research staff member at IBM T. J.

April 8, 2020 | Research News |PFC

Charting a Course Toward Quantum Simulations of Nuclear Physics

In nuclear physics, like much of science, detailed theories alone aren’t always enough to unlock solid predictions. There are often too many pieces, interacting in complex ways, for researchers to follow the logic of a theory through to its end. It’s one reason there are still so many mysteries in nature, including how the universe’s basic building blocks coalesce and form stars and galaxies. The same is true in high-energy experiments, in which particles like protons smash together at incredible speeds to create extreme conditions similar to those just after the Big Bang.

December 23, 2019 | Research News |PFC

Synthetic Magnetism Leads Photons on a 2D Quantum Walk

Randomness governs many things, from the growth of cell colonies and the agglomeration of polymers to the shapes of tendrils that form when you pour cream into a cup of coffee.

Since as early as 1905, scientists have described these seemingly unrelated phenomena in a unified way: as random walks. By imagining that individual particles or molecules are constantly taking steps in a random direction, researchers have successfully modeled many of the complexities of classical physics.

December 17, 2019 | Research News |PFC

Remote Quantum Systems Produce Interfering Photons

Scientists at the Joint Quantum Institute (JQI) have observed, for the first time, interference between particles of light created using a trapped ion and a collection of neutral atoms. Their results could be an essential step toward the realization of a distributed network of quantum computers capable of processing information in novel ways.

October 18, 2019 | Research News |PFC

Hybrid Device among First to Meld Quantum and Conventional Computing

Researchers at the University of Maryland (UMD) have trained a small hybrid quantum computer to reproduce the features in a particular set of images.

October 14, 2019 | Research News |PFC

Stretched Photons Recover Lost Interference

The smallest pieces of nature—individual particles like electrons, for instance—are pretty much interchangeable. An electron is an electron is an electron, regardless of whether it’s stuck in a lab on Earth, bound to an atom in some chalky moon dust or shot out of an extragalactic black hole in a superheated jet. In practice, though, differences in energy, motion or location can make it easy to tell two electrons apart.

August 2, 2019 | Research News |PFC

Corkscrew photons may leave behind a spontaneous twist

Everything radiates. Whether it's a car door, a pair of shoes or the cover of a book, anything hotter than absolute zero (i.e., pretty much everything) is constantly shedding radiation in the form of photons, the quantum particles of light.

A twin process—absorption—is usually also present. As photons carry away energy, passers-by from the environment can be absorbed to replenish it. When absorption and emission occur at the same rate, scientists say that an object is in equilibrium with its environment. This often means that object and environment share the same temperature.

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Brief Reports

Subwavelength optical lattices for atomic dark states

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

Photoic chip guides single photons past bends in the road

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

Nanowire experiment boosts confidence in Majorana sighting

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

Mimicking cosmology in cold atom systems

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

Brownian motion of solitons in a Bose–Einstein condensate

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

Interacting Atomic Interferometry for Rotation Sensing Approaching the Heisenberg Limit

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

Modal interference in optical nanofibers for sub-Angstrom radius sensitivity

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

Observation of a discrete time crystal

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

Demonstration of a small programmable quantum computer with atomic qubits

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

Many-body localization in a quantum simulator with programmable random disorder

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

Geometrical Pumping with a Bose-Einstein Condensate

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 phases of spin-1 spin-orbit-coupled Bose gases

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

Anomalous broadening in driven dissipative Rydberg systems

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

Parafermionic zero modes in ultracold bosonic systems

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

Visualizing edge states with an atomic Bose gas in the quantum Hall regime

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

Statistical Transmutation in Floquet Driven Optical Lattices

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

Realization of a Quantum Integer-Spin Chain with Controllable Interactions

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

Rayleigh scattering in an optical nanofiber as a probe of higher-order mode propagation

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

Nearly Linear Light Cones in Long-Range Interacting Quantum Systems

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

Nanoscale probing of image dipole interactions in a metallic nanostructure

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

Stoner Ferromagnetism in a Thermal Pseudospin-1/2 Bose Gas

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.

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

Chiral magnetism and spontaneous spin Hall effect of interacting Bose superfluids

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

Topologically Robust Transport of Photons in a Synthetic Gauge Field

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

Hysteresis in a quantized superfluid ‘atomtronic’ circuit

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

Second-harmonic generation using -quasi-phasematching in a GaAs whispering-gallery-mode microcavity

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

Imaging topological edge states in silicon photonics

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

Mode reconstruction of a light field by multi-photon statistics

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

Demonstrating Highly Symmetric Single-Mode, Single-Photon Heralding Efficiency in Spontaneous Parametric Downconversion

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

Emergence and Frustration of Magnetism with Variable-Range Interactions in a Quantum Simulator

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

A quantum logic gate between a solid-state quantum bit and a photon

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

Spatially addressable readout and erasure of an image in a gradient echo memory

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

Ytterbium in quantum gases and atomic clocks: van der Waals interactions and blackbody shifts

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

Interplay of disorder and interaction in Majorana quantum wires

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

Universal Monopole Scaling near Transitions from the Coulomb Phase

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

Disorder-driven loss of phase coherence in a quasi-2D cold atom system

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

Temporally multiplexed storage of images in a gradient echo memory

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

The Peierls substitution in an engineered lattice potential

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

Low-Photon-Number Optical Switching with a Single Quantum Dot Coupled to a Photonic Crystal Cavity

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

Bond order solid of two-dimensional dipolar fermions

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

Synthetic Partial Waves in Ultracold Atomic Collisions

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

Optomechanically induced non-reciprocity in microring resonators

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

Topological semimetal in a fermionic optical lattice

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

Coalescence of Single Photons Emitted by Disparate Single-Photon Sources

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

Kaleidoscope of Exotic Quantum Phases in a Frustrated XY Model

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

Onset of a Quantum Phase Transition with a Trapped Ion Quantum Simulator

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

Floquet Topological Insulator in Semiconductor Quantum Wells

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

Atomtronics: A superfluid switch

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

Ultrafast Gates in Atomic Qubits

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

Spin-Orbit Coupling in Ultracold Neutral Atoms

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

Phases of a 2D Bose Gas in an Optical Lattice

“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

A Quantum Random Number Generator

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

Entangling Atoms with Optical Frequency Combs

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

Indistinguishable Photons from Separate Quantum Dots

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 Made Practical?

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

'Synthetic Magnetism' Demonstrated

Entangled Photons from Quantum Dots

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

Tuning Interactions Between Dots and Cavities

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

Tunable Spin-Spin Couplings Between Trapped Ions

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

A Plan for Hybrid Entanglement

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

Quantum Phase Detection in Paired Superfluids

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

Mysterious Motion-Damping Explained

Opening a Remote Quantum Gate

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

Behavior Modification for Neutral Atoms

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

Modeling the Transistor of the Future

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

Dressing Rubidium Atoms with Laser Light

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

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

Teleportation Between Distant Atoms

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