Nonreciprocal devices, in which electrical or optical signals travel in one direction only, are essential for telecommunication and quantum applications, but they are often both lossy and bulky to implement. A prototype device demonstrates nonreciprocity in a microwave optomechanical circuit that allows for dynamic isolation control while avoiding the need for large magnetic fields.

Ensembles of electron spins can couple to one another and emit collectively in a process known as “superradiance.” Researchers demonstrate strong coupling of a superradiant ensemble of donor spins in silicon, paving the way for future studies of entanglement and implementing a spin ensemble quantum memory.

Results from a new method of analyzing neutron-scattering data from polymer samples under deformation may challenge the prevailing “tube model” of polymer motion.

Current protocols for securely delegating computation to remote quantum computers require some form of quantum communication, thus limiting secure access to future cloud-based quantum computing resources. A new analysis shows that it is possible to hide critical aspects of a computation delegated to a quantum computer using only classical communication.

DNA’s many tangles and loops make it difficult to take an accurate inventory of in vitro genetic material. Now, researchers show how DNA can be wrapped in a single strand around a rotating micrometer-sized cylinder.

General relativity and quantum mechanics are at odds in the extreme environments of black holes, but black holes can only be observed from large distances. Scientists propose a solid-state “black hole on a chip” using the interface between a three-dimensional topological insulator and an ordinary superconductor.

The quantum information processing techniques of the future may rely on photon-photon interactions, which researchers now theoretically demonstrate are possible using polaritons, a type of quasiparticle.

A new model of language evolution assumes that changes in the spatial boundaries between dialects are controlled by a surface tension effect.

Theories for understanding two-dimensional electronic systems, such as certain exotic states that could be useful for quantum computing, are not as well developed as their one-dimensional counterparts. A new mathematical analysis extends a successful theory for one-dimensional conductors—Luttinger liquid theory—to two dimensions, revealing novel properties of these systems.

Controlling the electron spin could be an effective way to store and manipulate information in quantum devices, but it is challenging because spins randomize over time. A novel technique demonstrates, experimentally, a way to manipulate spin as an electron travels across a chip while being protected from randomization.

Two experimental groups have taken a step towards observing the “scrambling” of information that occurs as a many-body quantum system thermalizes.

A mode-selective nonlinear optics technique is used to extract a single photon from multimode light, a key operation for hybrid optical quantum information processing.

Theoretically characterizing materials that are strongly correlated has been a long-standing challenge. A new method models the atomic excitations of such materials with high resolution at all energies

Digital electronics are based on deterministic units called bits that can have one of two values, 0 and 1. New theoretical work suggests that circuits built out of probabilistic units that fluctuate randomly in value between 0 and 1 can be used to perform multiple functions: A multiplier, for example, can also function as a factorizer.

Spectroscopy of soft matter such as biological material suffers from low contrast and low resolution. A prototype of a new instrument concept that combines Raman and Brillouin spectrometry, however, demonstrates superior performance for studying the chemical makeup and mechanical properties of matter in a variety of applications.

Physicists have long sought to understand how quantum dynamics generates the nonlocal correlations known as entanglement. Theoretical models are proposed to explain the growth of entanglement over time in different numbers of spatial dimensions.

Experimentally confining radiation to certain limited directions (“needle radiation”) has numerous practical applications in wave-matter interaction disciplines. A theoretical proposal for realizing such superdirectivity is presented.

Spin torque is a promising technique for flipping magnetic orientation in nanomagnets used in low-power computer memories, but accurately measuring this torque is difficult. A new experiment shows how ferromagnetic resonance can characterize spin-torque vectors at an Fe-MgO interface.

A physically sound understanding of how radiation-induced damage originates and accumulates in a material has long eluded researchers. New simulations show that the roughness of the enthalpy landscape determines the extent of this damage.

Realizing an exotic phase of matter known as a quantum spin liquid has long eluded condensed-matter physicists. Now strong evidence is found that a particular class of exotic states of matter called a Dirac spin liquid is realized in a popular model of numerous magnets.

A new model extends the definition of causality to quantum-mechanical systems.

A simple model of an autonomous quantum clock yields a quantitative connection between the clock’s thermodynamic cost and its accuracy and resolution.

Topological invariants, properties of a system that remain unchanged by small deformations, are key to modern understanding of phases of matter but have yet to be directly detected by experiment. A new quantum simulation shows how quantum walks can be used to measure topological invariants for the first time.

Light interacting with an ensemble of atoms can be used in quantum information processing, but the efficiency of performing any given task is limited by spontaneous emission of photons into channels that are not usable. A new analysis shows how interference among light emitted by nearby atoms can dramatically improve this efficiency and provide a much more powerful platform.

The physics of strongly correlated matter, where interactions among atoms and particles can lead to exotic macroscopic properties, is difficult to understand theoretically. A realization of the leading theoretical model provides insight into these correlations from thermodynamic measurements.

Predicting the motions of quantum particles in large ensembles is mathematically complex and computationally expensive. A new theoretical method shows promise for predicting the dynamics of a gas of quantum particles by accurately describing the dynamics of one-dimensional strongly interacting bosons.

The tendency for a macroscopic system to reach equilibrium could depend on underlying quantum behaviors, but showing that this can happen in a reasonable time is difficult. A new analysis demonstrates that for certain classes of physically relevant observables, conditions exist where this is possible.

Computer simulations are used to model the phase change that occurs as glasses transition from a liquid phase to a so-called “ideal glass phase.”

Multiple descriptions of the half-filled Landau level, an exotic phase of matter seen in two-dimensional electron gases, have led to incompatible pictures that are widely believed to represent two distinct phases of matter. A new analysis suggests that this is not the case and that these descriptions are functionally equivalent.

Multidimensional coherent optical spectroscopy is currently one of the most powerful tools for investigating complex quantum-mechanical systems, but resolving energy splitting on megahertz scales remains a challenge. A new investigation shows how two-dimensional Fourier transform spectroscopy can be adapted to evaluate spin splitting of ground-state electrons.

Pattern formation in optical devices known as passive Kerr resonators has been studied for decades, but recent theoretical work has suggested the existence of entirely new dynamics when operated in the highly nonlinear regime. New experiments confirm these predictions, which could lead to innovative new sources of laser-like light and provide new insight into nonlinear dynamics and pattern formation.

Weyl points, characterized as nodal points in the band structure of solids, can give rise to novel physical properties but are difficult to investigate experimentally. A new analysis expands the scope of Weyl points using synthetic dimensions, paving the way for greater flexibility in future investigations.

New experiments reveal a diverse family of polygon patterns forming spontaneously in a fluid of polaritons—quasiparticles comprised of photons coupled to electric dipoles. The observations could lead to new insights in pattern formation in nonlinear optical systems as well as in quantum statistics.

Driving of many-body quantum systems leads to steady-state behavior not seen when the system is at equilibrium. While the outcome of a periodic drive is well explored, the same can’t be said for aperiodic drives. A new analysis shows that aperiodic drives can lead to novel steady-state behavior not seen in periodically driven systems.

The Born-Oppenheimer approximation, used to predict atomic motions in quantum mechanics, leads to well-known inconsistencies caused by neglecting the effect of electron motion induced by nuclear evolution. A new theoretical paradigm resolves this problem, paving the way for high-precision predictions of vibrational frequencies of complex molecules.

Researchers have used a free-electron laser to produce vortex radiation at extreme-ultraviolet wavelengths.

Artificial molecules built from superconducting circuits can potentially be used as probes of external fields that cannot be studied with devices built from naturally occurring atoms. A new study demonstrates how the magnetic moment of a molecule built from two artificial fluxonium atoms changes in response to an external magnetic field.

Machine learning has strong potential as a tool for understanding how to classify phases in condensed matter physics. A new investigation shows that an artificial neural network can be trained to identify changes in the collective magnetic properties of electrons on a lattice and predict trends in the transition when some of the electrons are removed.

A flocking model that describes birds and cells exhibits topological features when the moving entities are confined to a curved surface.

Nitrogen-vacancy centers—a type of atom-sized defect in diamonds—have potential for use as quantum bits in quantum information technologies. However, low rates of entanglement between the defect spin and the photons they produce hamper the mediation of long-distance connections. A new experiment shows a way around this limitation by employing a tunable, miniaturized Fabry-Pérot microcavity.

Analysis of the large amounts of image data requires increasingly expensive and time-consuming computational resources. Quantum computing may offer a shortcut. A new edge-detection algorithm based on a specific quantum image representation shows exponentially faster performance compared to classical methods.

Reconstruction of the Fermi surface in the cuprate YBa${}_2$Cu${}_3$O${}_y$ is thought to be caused by one of two types of charge-density waves. Identifying which one is responsible could help researchers understand the high-temperature superconductivity that cuprates exhibit. New experiments show that short-range two-dimensional waves lead to Fermi surface reconstruction.

Antidot graphene, a sheet of carbon atoms with carefully arranged patterns of holes, has electronic properties that differ from pristine graphene. One way to quantify this difference is with a mathematical quantity called Berry curvature. A new analysis shows that antidot graphene has nonzero curvature, which leads to interesting electron behavior.

A tiny engine can surpass the Carnot limit of efficiency when researchers engineer the thermal properties of the environment.

Brains process information reliably despite the presence of noise introduced by their molecular machinery. New computer simulations of neurons show that these cells might use noise to their advantage by employing dendrites to detect low-intensity signals and using the main cell body to process more powerful signals.

Diffractive optical components play a huge role in many applications, but they only work optimally when incident radiation hits them at a specific preordained angle. A new concept known as a multichannel metasurfaces, however, promises to control light coming and going from multiple directions at the same time, opening up intriguing possibilities for a range of novel optical devices.

Chaos in quantum systems of many interacting particles leads to information scrambling, which underlies diverse fields from black holes to entanglement production. A new analysis determines a fundamental speed at which information spreads in a common example of a quantum many-body system, which could lead to broader insights into information dynamics.

Preserving the delicate states that store information in a quantum computer when dealing with a noisy environment is a considerable challenge, and many researchers are turning to hardware- and software-based topological protection as a solution. A new paradigm based on error-correcting color codes combines the advantages of both hardware and software and enables a scalable approach to fault-tolerant quantum computing.

In quantum computing, atomic ensembles can efficiently map “flying” photonic qubits onto stationary qubits. These absorbed photons, however, end up encoded in delocalized states that preclude local processing. A new concept called a “quantum spin lens” could focus delocalized excitations onto a single atom, which can then be manipulated using standard quantum computing tools.

Magnetometers based on the spins of single electrons offer a way to precisely characterize magnetic fields at microscopic scales but are highly sensitive to noisy environments. New experiments show a way to build a more robust single-spin magnetometer using entangled calcium ions.

Different theories can be used to describe the same behavior in quantum matter, a concept known as duality. A new analysis uses duality to connect ideas in quantum electrodynamics with a type of quantum magnet known as a deconfined quantum critical point and reveal new properties of both.

Proving an equivalence between two theories—one that describes a transition between two kinds of insulating states and another that models changes between spin states—would offer a step toward a unified theoretical understanding of different condensed-matter systems. New computer simulations provide evidence for this duality by showing that the critical points of these two theories have identical properties.

Surface reconstructions in cleaved crystals are generally thought to be driven by charge transfer between surface atoms. New calculations and experiments with rutile titanium dioxide exhibit a radically different mechanism based on charge trapping, which could open up novel ways of designing crystal surfaces for a range of applications.

Kondo insulators exhibit strong electronic interactions and topological protection, making them a good platform for studying connections between these two fields. New experiments show that a type of magnetic oscillation (the de Hass-van Alphen effect) originates in the surface of a Kondo insulator, bolstering evidence for topologically protected surface states.

When light reflects off a mirror, its intensity and phase become quantum correlated as a result of radiation pressure. These correlations could be used to erase quantum backaction, which poses a fundamental limit to the precision of interferometric displacement measurements. For the first time, these correlations are observed and exploited in a room-temperature interferometer, which could lead to advances in quantum-enhanced metrology.

Detecting anomalous clusters within networks is vital to cybersecurity in detecting attacks and intrusions, but such analysis is typically ad hoc with no overarching, unifying methodology. A new analysis shows how layer aggregation can be used in a variety of time-varying networks as a filter for preprocessing data to allow the detection of communities that would otherwise go unnoticed.

Understanding the behavior of topological phases of matter in the presence of strong interactions and correlations is one of the big challenges in modern physics. New theoretical work analyzes a potential platform for addressing these challenges and proposes how it might be implemented in a one-dimensional optical lattice.

The behavior of electrons near quantum critical points, such as magnetic phase transitions at temperatures approaching absolute zero, are of vital interest but are extremely challenging to understand. New computer simulations solve this problem, exactly, for one example of these strange metals and reveal a new type of quantum critical point.

Understanding the collective behavior of many interacting electrons is a key challenge in fundamental physics and materials design. A benchmark study characterizes the accuracy and abilities of 16 methods for many-electron computations and applies these insights to determining the equation of state for an infinite chain of hydrogen atoms.

A new method for identifying and analyzing Markov states from molecular dynamics trajectories offers a novel and simple approach to analyzing the complex behavior in molecular processes, such as those seen in biological systems.

In disordered quantum systems, magnetic domains might be localized, indefinitely preserving their initial states. A theoretical analysis shows that disorder is not necessary for protecting this order and can be accomplished via quasiperiodic modulations.