We theoretically study the bound states of interacting photons propagating in a waveguide chirally coupled to an array of atoms. We demonstrate that the bound photon pairs can concentrate at the edge of the array and link this to the non-Hermitian skin effect. Unlike tight-binding non-Hermitian setups, the bound states in the waveguide-coupled array exhibit infinite radiative lifetimes when the array has an infinite size. However, in a finite array, non-Hermiticity and localization of bound pairs emerge due to their chiral dissociation into scattering states. Counterintuitively, when the photons are preferentially emitted to the right, the bound pairs are localized at the left edge of the array and vice versa.

Non-Gaussianity, a distinctive characteristic of bosonic quantum states, is pivotal in advancing quantum networks, fault-tolerant quantum computing, and high-precision metrology. Verifying the quantum nature of a state, particularly its non-Gaussian features, is essential for ensuring the reliability and performance of these technologies. However, the specific properties required for each application demand tailored validation thresholds. Here, we introduce a hierarchical framework comprising absolute, relative, and qubit-specific thresholds to assess the non-Gaussianity of local coherences. We illustrate this framework using heralded optical non-Gaussian states with the highest purities available in optical platforms. This comprehensive framework presents the first detailed evaluation of number state coherences and can be extended to a wide range of bosonic states.

We develop a theoretical model to investigate wave propagation in media with random time-varying properties, where temporal fluctuations lead to complex scattering dynamics. Focusing on the ensemble-averaged field, we derive an exact expression for the average Green’s function in the presence of finite temporal disorder, and extend the analysis to the thermodynamic limit. In contrast to spatial disorder, causality prevents recurrent scattering, allowing us to achieve a nonperturbative solution. We introduce an effective medium description providing a simple analysis of the propagation regimes. Our findings offer new insights into wave dynamics in temporally disordered media, with potential applications in time-varying metamaterials, dynamic sensing, and imaging in turbulent or chaotic environments.

We investigate the spontaneous breaking of subsystem symmetry in a stack of two-dimensional Fermi liquid metals, each maintaining a subsystem number conservation symmetry, driven by interlayer exciton condensation. The resulting Goldstone modes in this broken symmetry phase couple to the quasiparticle current perpendicular to the layers. This coupling, which remains nonzero for small momentum transfers, leads to the emergence of a three-dimensional anisotropic marginal Fermi liquid state when the number of layers is sufficiently large. We propose a possible experimental realization of this phenomenon in two-dimensional multilayer van der Waals heterostructures. Using self-consistent mean-field calculations, we characterize the subsystem symmetry-broken metallic state and examine the effects of fluctuations on its physical properties within the random phase approximation. We find that these fluctuations produce additional logarithmic enhancements to the specific heat at low temperature, specifically $C\sim T[\log (1/T){]}^2$.

Circularly polarized phonons offer a new route for mediating angular momentum in solids. However, controlling phonon angular momentum without altering the material’s structure or composition remains challenging. Here, we demonstrate the nonvolatile switching of angular momentum-carrying phonons by leveraging intrinsic ferrimagnetism in an insulator. We find a pair of chiral phonons with giant energy splitting, reaching 20% of the phonon frequency due to spontaneously broken time-reversal symmetry. With a moderate magnetic field, the phonon angular momentum of the two chiral phonon branches can be switched along with the magnetization. Notably, near the critical temperature, the effective phonon magnetic moment is enhanced, reaching 2.62 Bohr magneton, exceeding the moment of a magnon. A microscopic model based on phonon-magnon coupling accounts for the observations. Furthermore, we identify two types of phononic domains with opposite phonon Zeeman splitting and propose the existence of topologically protected phononic edge modes at domain boundaries. These results demonstrate effective manipulation of chiral phonons with magnetism, and pave the way for engineering chiral phononic domains on the micrometer scale.

Semiconductor spin qubits are an attractive platform for quantum computing, but their performance is degraded primarily by fluctuating electromagnetic environments. We introduce the concept of ballast charges, which are induced charges on the surface of an additional screening layer situated below the qubits. The counteractive behavior of these charges can significantly reduce the power spectral density associated with fluctuations from two-level systems that contribute to charge noise. Our simulations show that the dephasing time of a single-spin qubit in a Si/SiGe device increases by a factor of 4 to 6 on average when using this method. We also discuss the physical implementation and potential challenges of this approach.

We construct an ensemble of two-dimensional nonintegrable quantum circuits that are chaotic but have a conserved particle current, and thus a finite Drude weight. The long-wavelength hydrodynamics of such systems is given by the incompressible Navier-Stokes equations. By analyzing circuit-to-circuit fluctuations in the ensemble we argue that these are negligible, so the circuit-averaged value of transport coefficients like the viscosity is also (in the long-time limit) the value in a typical circuit. The circuit-averaged transport coefficients can be mapped onto a classical irreversible Markov process. Therefore, remarkably, our construction allows us to efficiently compute the viscosity of a family of strongly interacting chaotic two-dimensional quantum systems.

Our current understanding of quantum chaos in many-body quantum systems hinges on the random matrix theory (RMT) behavior of eigenstates and their energy level statistics. Although RMT has been remarkably successful in describing “coarse” features of many-body quantum Hamiltonians in chaotic regimes, such as the Wigner-Dyson level spacing statistics or the volume-law behavior of eigenstate entanglement entropy, it remains a challenge to describe their “finer” features, particularly those arising from spatial locality. Here, we show that we can accurately describe the statistical behavior of eigenstate ensembles in many-body Hamiltonians by using pure random states with physical constraints that capture the essential features of the Hamiltonian, specifically spatial locality and symmetries. We demonstrate our approach on local spin Hamiltonians with a scalar U(1) charge. By constructing ensembles of constrained random states that account for two commuting scalar charges playing the role of energy and magnetization, we describe the patterns of entanglement of midspectrum eigenstates beyond their average volume-law behavior, including $O(1)$ corrections and fluctuations, analytically and numerically. When defining the correspondence between quantum chaotic eigenstates in many-body Hamiltonians and RMT ensembles, our work highlights the important role played by spatial locality in describing universal features beyond the volume-law behavior.

State-of-the-art quantum simulators permit local temporal control of interactions and midcircuit readout. These capabilities open the way toward the exploration of intriguing nonequilibrium phenomena. We illustrate this with a kinetically constrained many-body quantum system that has a natural implementation on Rydberg quantum simulators. The evolution proceeds in discrete time and is generated by repeatedly entangling the system with an auxiliary environment that is monitored and reset after each time step. Despite featuring an uncorrelated infinite-temperature average stationary state, the dynamics displays coexistence of fast and slow space-time regions in stochastic realizations of the system state. The time record of measurement outcomes on the environment serves as natural probe for such dynamical heterogeneity, which we characterize using tools from large deviation theory. Our Letter establishes the large deviation framework for discrete-time open quantum many-body systems as a means to characterize complex dynamics and collective phenomena in quantum processors and simulators.

Modifications of standard general relativity that bring torsion into the game have a long-standing history. However, no convincing arguments exist for or against its presence in physically acceptable gravity models. In this Letter, we provide an argument based on spectral geometry (using methods of pseudodifferential calculus) that suggests that the torsion shall be excluded from the consideration. We demonstrate that there is no well-defined functional extending to the torsion-full case of the spectral formulation of the Einstein tensor.

We investigate $\mathrm{\Lambda }$ production in semi-inclusive deep-inelastic scattering using a polarized lepton beam and find that the spin transfer is significantly suppressed by target fragmentation. As further demonstrated by a model estimation, experimental data can be well described once the target fragmentation is taken into account, which alleviates the tension with calculations solely based on current fragmentation. Our findings suggest that, at the energies of existing fixed-target experiments, the separation of current and target fragmentation regions is not distinct. Spin transfer as well as other spin effects offers a sensitive probe into the origin of the produced hadron.

Energy correlators have recently come to the forefront of jet substructure studies at colliders due to their remarkable properties: they naturally separate physics at different scales, are robust to contamination from soft radiation, and offer a direct connection with quantum field theory. The current parametrization used for energy correlators, however, is based on redundant pairwise angles with complex phase space restrictions. In this Letter, we introduce a new parametrization of energy correlators that features a simpler phase space structure and preserves information about the orientation of jet constituents. Further, our parametrization drastically reduces the computational cost to compute energy correlators on experimental data; whereas the time to compute a traditional projected $N$-point energy correlator scales as $M^N/N!$ on a jet with $M$ particles, our new parametrization achieves a scaling of $M^2\ln M$, remarkably independently of $N$. Even for $N=3$, this improved scaling is particularly important for studies of heavy ion collisions, and higher values of $N$ will enable new qualitative understanding of gauge theories. Theoretical calculations for our new energy correlators differ from those of traditional parametrizations only at next-to-next-to-leading logarithmic accuracy and beyond, and we expect that our simpler phase space structure will simplify those calculations. We also discuss how to extend our parametrization to resolved $N$-point energy correlators that encode angular distances between greater numbers of particles, yielding intuitive visualizations of jet substructure that are qualitatively different for different jet samples. We propose two possible generalizations for probing multiprong jets and testing jet scaling behavior.

We present a study on neutron-rich tin ($Z=50$) isotopes beyond the doubly closed shell of $N=82$ through high-precision mass measurements, including the first-ever measurements of the masses of ${}^{136}\mathrm{Sn}$, ${}^{137}\mathrm{Sn}$, and ${}^{138}\mathrm{Sn}$ isotopes. These measurements enhance our understanding of the nuclear structure and astrophysical nucleosynthesis in this previously unexplored region. The new mass data are used for evaluation of the final abundances of mass numbers $A=135$ and 137 in $r$-process network calculations. Our findings reveal a notable change in the empirical pairing gap for tin isotopes beyond the $N=82$ closed shell and a shift in the two-neutron-separation energy slope compared to heavier elements above the shell closure. A new set of ab initio calculations effectively describes these observed trends.

The phase diagram of the heavy fermion compound ${\mathrm{UTe}}_2$ contains multiple superconducting phases, several of which show characteristics of odd-parity pairing. We have investigated the pressure dependence of the superconducting transition in high-quality crystals of ${\mathrm{UTe}}_2$ by tracking its signature in the magnetic susceptibility $\chi (T)$. A single, sharp superconducting transition is observed at low pressures $<0.3\mathrm{GPa}$. At higher pressure, a second feature emerges in $\chi (T)$, which is located at the lower-temperature superconducting phase boundary previously identified in specific heat measurements. This second transition anomaly in $\chi (T)$ can be attributed to a step change in the London penetration depth, providing direct evidence for a change in the superconducting order parameter of ${\mathrm{UTe}}_2$. Thermodynamic constraints suggest that the low temperature, high pressure superconducting state is distinct from zero pressure superconductivity as well as from the high pressure, high temperature superconducting state, raising the possibility of multicomponent superconductivity in high pressure ${\mathrm{UTe}}_2$.

We develop a theory of edge excitations of fractonic systems in two dimensions, and elucidate their connections to bulk transport properties and quantum statistics of bulk excitations. The system we consider has immobile point charges, dipoles constrained to move only along lines perpendicular to their moment, and freely mobile quadrupoles and higher multipoles, realizing a bulk fractonic analog of fractional quantum Hall phases. We demonstrate that a quantized braiding phase between two bulk excitations is obtained only in two cases: when a point quadrupole braids around an immobile point charge, or when two non-orthogonal point dipoles braid with one another. The presence of a boundary edge in the system entails two types of gapless edge excitation modes, one that is fractonic with immobile charges and longitudinal dipoles, and a second non-fractonic mode consisting of transverse dipoles. We derive a novel current algebra of the fractonic edge modes. Further, investigating the effect of local edge-to-edge tunneling on these modes, we find that such a process is a relevant perturbation suggesting the possibility of edge deformation.

Causality, a cornerstone of physical laws, fundamentally links a system’s structural characteristics to its wave interaction properties, such as the minimum thickness of acoustic absorbers required for specific absorption spectra. Traditional causality principles for sound absorption are derived under the assumption of adiabatic sound propagation. In this Letter, we propose a generalized causal framework that incorporates isothermal processes, accounting for nonslip boundary conditions at the fluid-solid interface. These conditions introduce velocity and temperature gradients, challenging the conventional adiabatic assumption. To validate our framework, we analyze two distinct absorber types: a metamaterial with multiresonant units and a metafoam with multilayer double-porosity structures. Our theoretical and experimental studies reveal that absorber thickness can exceed the adiabatic limit, being instead governed by isothermal constraints. This paradigm shift deepens the understanding of sound absorption mechanisms and paves the way for designing high-performance acoustic devices that approach fundamental performance limits.

Entangled photons are crucial resources for quantum information processing. Here, we present an ultrabright polarization-entangled photon source based on a periodically poled lithium niobate waveguide designed for practical quantum communication networks. Using a 780 nm pump laser, the source achieves a pair generation rate of $2.4\times {10}^{10}\mathrm{pairs}/\mathrm{s}/\mathrm{mW}$. Remarkably, the entangled photons are bright enough to be detected by a power meter, reaching a power of 17.9 nW under a pump power of 3.2 mW. We demonstrate the practicality of the source by conducting quantum key distribution experiments over long-distance fiber links. Wavelength-division multiplexing was employed to enhance the key generation, and nonlocal dispersion compensation was implemented to ensure precise timing coincidence measurements across a broad spectral range. By utilizing nine pairs of wavelength channels, the system achieved the applicable secure key rates of up to $440.80\mathrm{bits}/\mathrm{s}$ over 200 km with a 62 dB loss and extended the maximum secure key generation distance to 404 km. These results demonstrate the potential of wavelength-multiplexed polarization-entangled photon sources for high-speed, long-distance quantum communication, positioning them as key components for future large-scale quantum networks.