A 3D fully kinetic simulation shows that the lower-hybrid drift instability disturbs the front of magnetic reconnection outflow jets and additionally causes energy dissipation. The result is very consistent with a disturbance observed at the dipolarization front (DF) in Earth’s magnetotail by the Magnetospheric Multiscale (MMS) mission. A fully kinetic dispersion relation solver, validated by the MMS observations, further predicts that the disturbance of the reconnection jet front could occur over different parameter regimes in space plasmas including Earth’s DF and solar flares.

In high-mobility materials, conduction electrons can form a viscous fluid at low temperatures. We demonstrate that in a high-frequency flow of a two-dimensional electron fluid in a magnetic field the two types of excitations can coexist: those of the shear stress (previously unknown transverse magnetosound) and those associated with the charge density (conventional magnetoplasmons). The dispersion law and the damping coefficient of transverse magnetosound originate from the time dispersion of the viscosity of the fluid. Both the viscoelastic and the plasmonic components of the flow exhibit the recently proposed viscoelastic resonance that is related to the own dynamics of shear stress of charged fluids in a magnetic field. We argue that the generation of transverse magnetosound, manifesting itself by the viscoelastic resonance, is apparently responsible for the peak in photoresistance and peculiarities in photovoltage observed in ultrahigh-mobility GaAs quantum wells.

We present a complete analysis of the linearized dynamics of active solids with uniaxial orientational order, taking into account a hitherto overlooked consequence of rotation invariance. Our predictions include a purely active response of two-dimensional orientationally ordered solids to shear, the possibility of stable active solids with quasi-long-range order in two dimensions and long-range order in three dimensions, generic instability of the solid for one sign of active forcing, and the instability of the uniaxially ordered phase in momentum-conserved systems for large active forcing irrespective of its sign.

We bootstrap the $S$ matrix of massless particles in unitary, relativistic two dimensional quantum field theories. We find that the low energy expansion of such $S$ matrices is strongly constrained by the existence of a UV completion. In the context of flux tube (FT) physics, this allows us to constrain several terms in the $S$ matrix low energy expansion or—equivalently—on Wilson coefficients of several irrelevant operators showing up in the FT effective action. These bounds have direct implications for other physical quantities; for instance, they allow us to further bound the ground state energy as well as the level splitting of degenerate energy levels of large FTs. We find that the $S$ matrices living at the boundary of the allowed space exhibit an intricate pattern of resonances with one sharper resonance whose quantum numbers, mass, and width are precisely those of the world-sheet axion proposed by Athenodorou, Bringoltz, and Teper and Dubovsky, Flauger, and Gorbenko. The general method proposed here should be extendable to massless $S$ matrices in higher dimensions and should lead to new quantitative bounds on irrelevant operators in theories of Goldstones and, also, in gauge and gravity theories.

Preparing mechanical systems in their lowest possible entropy state, the quantum ground state, starting from a room temperature environment is a key challenge in quantum optomechanics. This would not only enable creating quantum states of truly macroscopic systems, but at the same time also lay the groundwork for a new generation of quantum-limited mechanical sensors in ambient environments. Laser cooling of optomechanical devices using the radiation pressure force combined with cryogenic precooling has been successful at demonstrating ground state preparation of various devices, while a similar demonstration starting from a room temperature environment remains an outstanding goal. Here, we combine integrated nanophotonics with phononic band gap engineering to simultaneously overcome prior limitations in the isolation from the surrounding environment and the achievable mechanical frequencies, as well as limited optomechanical coupling strength, demonstrating a single-photon cooperativity of 200. This new microchip technology allows us to feedback cool a mechanical resonator to around 1 mK, near its motional ground state, from room temperature. Our experiment marks a major step toward accessible, widespread quantum technologies with mechanical resonators.

Deterministic quantum computation with one qubit (DQC1) is iconic in highlighting that exponential quantum speedup may be achieved with negligible entanglement. Its discovery catalyzed a heated study of general quantum resources, and various conjectures regarding their role in DQC1’s performance advantage. Coherence and discord are prominent candidates, respectively, characterizing nonclassicality within localized and correlated systems. Here we realize DQC1 within a superconducting system, engineered such that the dynamics of coherence and discord can be tracked throughout its execution. We experimentally confirm that DQC1 acts as a resource converter, consuming coherence to generate discord during its operation. Our results highlight superconducting circuits as a promising platform for both realizing DQC1 and related algorithms, and experimentally characterizing resource dynamics within quantum protocols.

We present a variational approach for quantum simulators to realize finite temperature Gibbs states by preparing thermofield double (TFD) states. Our protocol is motivated by the quantum approximate optimization algorithm and involves alternating time evolution between the Hamiltonian of interest and interactions which entangle the system and its auxiliary counterpart. As a simple example, we demonstrate that thermal states of the 1D classical Ising model at any temperature can be prepared with perfect fidelity using $L/2$ iterations, where $L$ is system size. We also show that a free fermion TFD can be prepared with nearly optimal efficiency. Given the simplicity and efficiency of the protocol, our approach enables near-term quantum platforms to access finite temperature phenomena via preparation of thermofield double states.

In this Letter, we propose that the x-ray and the TeV observations in the vicinity of Geminga can be understood in the framework of anisotropic diffusion of injected electrons or positrons. This interpretation only requires the turbulence in the vicinity of Geminga to be sub-Alfvénic with the local mean magnetic field direction approximately aligned with our line of sight towards Geminga, without invoking extreme conditions for the environment, such as an extremely small diffusion coefficient and a weak magnetic field of submicrogauss as suggested in previous literature.

We present a new method of deriving the geometry of entanglement wedges in holography directly from conformal field theories (CFTs). We analyze an information metric called the Bures metric of reduced density matrices for locally excited states. This measures the distinguishability of states with different points excited. For a subsystem given by an interval, we precisely reproduce the expected entanglement wedge for two-dimensional holographic CFTs from the Bures metric, which turns out to be proportional to the anti–de Sitter metric on a time slice. On the other hand, for free scalar CFTs, we do not find any sharp structures like entanglement wedges. When a subsystem consists of two disconnected intervals, we manage to reproduce the expected entanglement wedge from holographic CFTs with the correct phase transitions, up to a very small error, from a quantity alternative to the Bures metric.

We propose a new way of breaking the Goldstone symmetry in composite Higgs models, restoring the global symmetry in the mixings between the elementary and composite fermions by completing the former to full representations of this symmetry. The Goldstone symmetry is in turn broken softly by vectorlike mass terms in the elementary sector only. The resulting softened explicit breaking allows for a light Higgs boson, as found at the LHC, and a heavy top quark, without the need of light top partners around the Goldstone scale $f\sim \mathrm{TeV}\ll m_{\mathrm{comp}}$., which remain elusive at the LHC, while we recover the standard scenario in the limit of infinite vectorlike masses.

The possibility to manipulate quantum coherence and interference, apart from its fundamental interest in quantum mechanics, is essential for controlling nonlinear optical processes such as high harmonic generation, multiphoton absorption, and stimulated Raman scattering. We show, analytically and numerically, how a nonlinear optical process via resonance Raman scattering (RRS) can be manipulated in a four-level double-$\mathrm{\Lambda }$ system by using pulsed laser fields. We find that two simultaneously excited RRS paths involved in the system can generate an ultimately destructive interference in the broad-bandwidth-limit regime. This, in turn, reduces the four-level system to an equivalent three-level system in a $V$ configuration capable of naturally vanishing RRS effects. We further show that this counterintuitive phenomenon, i.e., the RRS vanishing, can be prevented by transferring a modulated phase of the laser pulse to the system at resonance frequencies. This work demonstrates a clear signature of both quantum destructive and constructive interference by actively controlling resonant multiphoton processes in multilevel quantum systems, and it therefore has potential applications in nonlinear optics, quantum control, and quantum information science.

We investigate the nonlinear propagation of intense, two-cycle, carrier-envelope phase (CEP) stable laser pulses at $1.7\mu \mathrm{m}$ center wavelength in air. We observe CEP-dependent spectral interference in the visible part of the forward-propagating white light generated on propagation. The effect is robust against large fluctuations of the input pulse energy. This robustness is enabled by rigid clamping of both the peak optical field and the phase of the propagating waveform, which has been revealed by numerical simulations. The CEP locking can enhance the yield of the CEP-dependent strong-field processes in gaseous media with long-wavelength drivers, while the observed spectral interference enables single-shot, stand-off CEP metrology in the atmosphere.

Attosecond angular streaking (or “attoclock”) is an insightful technique for probing the ultrafast electron dynamics in strong laser fields. Up until recently, this technique relied solely on an accurate measurement of the photoelectron momentum distribution and has remained restricted to atomic targets. Here, we propose a novel attosecond angular streaking scheme applicable to molecules, for which the ionic fragments of dissociative ionization are detected in the polarization plane of a close-to-circular polarized laser light. Our ionic attoclock measurements are consistent with theoretical results from a numerical solution of the time-dependent Schrödinger equation and an upper bound of 10 as on the tunneling time from the attoclock readings in the ${\mathrm{H}}_2$ molecule has been given, which is significantly smaller than any definitions of tunneling time available in the literatures.

We propose to use fermionic atoms with degenerate ground and excited internal levels ($F_g\to F_e$), loaded into the motional ground state of an optical lattice with two atoms per lattice site, to realize dark states with no radiative decay. The physical mechanism behind the dark states is an interplay of Pauli blocking and multilevel dipolar interactions. The dark states are independent of lattice geometry, can support an extensive number of excitations, and can be coherently prepared using a Raman scheme taking advantage of the quantum Zeno effect. These attributes make them appealing for atomic clocks, quantum memories, and quantum information on decoherence free subspaces.

Mixing of passive scalars in compressible turbulence does not obey the same classical Reynolds number scaling as its incompressible counterpart. We first show from a large database of direct numerical simulations that even the solenoidal part of the velocity field fails to follow the classical incompressible scaling when the forcing includes a substantial dilatational component. Though the dilatational effects on the flow remain significant, our main results are that both the solenoidal energy spectrum and the passive scalar spectrum assume incompressible forms, and that the scalar gradient essentially aligns with the most compressive eigenvalue of the solenoidal part, provided that only the solenoidal components are consistently used for scaling. A slight refinement of this statement is also pointed out.

The change in entropy of a system that is transferred between two states at different temperatures is measured in a two-dimensional plasma crystal experiment. One- and especially two-component dust clusters are confined in the plasma sheath and heated to different temperatures using laser manipulation. We find that entropies obtained from the phase space yield consistent results for, i.e., the heat capacity which shows excellent agreement with the Dulong-Petit law. The implications for the validity of basic thermodynamical principles in finite size complex (dusty) plasmas are discussed.