Exact numerical results for the dc magnetoconductivity tensor of the two-dimensional spatially disordered Yukawa-Sachdev-Ye-Kitaev (2D-YSYK) model on a square lattice, at first order in applied perpendicular magnetic field, are obtained from the self-consistent disorder-averaged solution of the 2D-YSYK saddle-point equations. This system describes fermions endowed with a Fermi surface and coupled to a bosonic scalar field through spatially random Yukawa interactions. The resulting local and energy-dependent fermionic self-energies are employed in the Kubo formalism to calculate the longitudinal and Hall conductivities, the Hall coefficient, the carrier mobility, and the cotangent of the Hall angle, at fixed fermion density. From the interplay between YSYK interactions and square-lattice embedding, and the non-Boltzmann frequency-dependent self-energies, we find nontrivial evolution of the magnetotransport coefficients as a function of temperature and YSYK interaction strength, notably a superlinear evolution of the Hall-angle cotangent and the inverse carrier mobility with temperature, concomitant with linear-in-temperature resistivity, in an extended crossover regime above the low-temperature marginal Fermi liquid ground state. Our model and results provide a controlled theoretical framework to interpret magnetotransport experiments, at linear order in applied magnetic field, in strange-metal phases found in strongly correlated solid-state electron systems.

We systematically investigate the effects of spin order and orbital polarization on the electronic and magnetic structures of nematic FeSe using the $\mathrm{LDA}+U$ method. While our calculations with on-site Coulomb repulsion $U\sim 4.5\mathrm{eV}$ can account for both the nonmagnetic state at ambient pressure and the phase transition to a stripe antiferromagnetic state at moderate pressure as observed experimentally, neither static spin order nor static orbital polarization can describe the experimental band dispersions from angle-resolved photoemission spectroscopy (ARPES) studies, due to the underestimate of quantum fluctuations. By employing a particle swarm optimization algorithm, we construct a tight-binding model with inclusion of correlation effects through seeking appropriate renormalization factors of kinetic energies, which successfully reproduce the ARPES results at various temperatures, highlighting the importance of correlations in FeSe.

Recent advances in constructing synthetic dimension provide a powerful tool for exploring exotic topological states of matter in high dimensions. Here, we report that the parity anomaly and associated half-integer quantized Hall conductance, arising in $2j+1$ (space-time) dimensions with a single or odd number of Dirac cones, can be realized by the boundary states of $n\mathrm{th}$-order topological insulators in ($2j+n$)-dimensional synthetic lattices. We establish a general bulk-boundary correspondence by integrating the nested Wilson loop theory with the time-reversal polarization at highly symmetric momenta; a set of $Z_2$ topological invariants are extracted, which determines the number and location of higher-order-boundary Dirac cones that are protected by time-reversal and reflection symmetries. We develop a general construction procedure for Hamiltonians supporting such higher-order topological parity anomaly. Moreover, we propose an experimental implementation scheme based on photonic synthetic dimensions and provide a method for probing the associated half-integer Hall conductance by the transmission spectra. Our work offers the realization and characterization of parity anomaly in general high-dimensional higher-order topological insulators and opens an avenue for exploring fundamental physics and possible photonic device applications enabled by manipulating Dirac cones.

The non-Hermitian skin effect, characterized by the extensive localization of bulk modes at the boundaries, has attracted significant attention as a hallmark feature of non-Hermitian topology. This localization invalidates the conventional Bloch band theory, necessitating an analysis under open boundary conditions even in the thermodynamic limit. The Amoeba formulation addresses this challenge by computing the spectral potential rather than the spectrum itself. Based on the (strong) Szegö limit theorem and its topological generalization, this approach reduces the evaluation of the potential to an optimization problem involving the Ronkin function. However, while the generalized Szegö limit theorem is formally applicable in arbitrary dimensions, its implementation is limited to single-band systems, and its applicability to multiband systems remains unclear even in one-dimensional systems. In this paper, we establish the Wiener-Hopf factorization (WHF) of the non-Bloch Hamiltonian as a powerful framework, providing a unified and rigorous foundation for Amoeba analysis in one-dimensional multiband systems. By combining the WHF with Hermitian doubling, we first elucidate the applicability criteria for the generalized Szegö limit theorem in multiband systems. We then show that the WHF provides the natural mathematical origin for the symmetry-decomposed Ronkin function in symmetry class ${\mathrm{AII}}^{†}$, leading to a rigorous proof of the generalized Szegö limit theorem for these systems and opening a path toward systematic generalizations to other symmetry classes.

The quantum geometric tensor and quantum Fisher information have recently been shown to provide a unified geometric description of the linear response of many-body systems. However, a similar geometric description of higher-order perturbative phenomena including nonlinear response in generic quantum systems is lacking. In this work, we develop a general framework for the time-dependent quantum geometry of many-body systems by treating external perturbing fields as coordinates on the space of density matrices. We use the Bures distance between the initial and time-evolved density matrix to define geometric quantities through a perturbative expansion. To lowest order, we derive a time-dependent generalization of the Bures metric related to the spectral density of linear response functions, unifying previous results for the quantum metric in various limits and providing a geometric interpretation of Fermi’s golden rule. At next order in the expansion, we define a time-dependent Bures-Levi-Civita connection for general many-body systems. We show that the connection is the sum of one contribution that is related to a second-order nonlinear response function, and a second contribution that captures the higher geometric structure of first-order perturbation theory. We show that in the quasistatic, zero-temperature limit for noninteracting fermions, this Bures connection reduces to the known expression for band-theoretic Christoffel symbols. Our work provides a systematic framework to explore many-body quantum geometry beyond the quantum metric and highlights how higher-order correlation functions can probe this geometry.

We consider hybrid systems consisting of a hole-doped semiconductor coupled to electronic states of finite-size superconductors, where the opposite sign of the masses in the two subsystems gives rise to insulating gaps at subband anticrossings. Consequently, increasing the coupling strength to the superconductor can paradoxically suppress the proximity-induced superconductivity in the semiconductor by enhancing these insulating gaps. We demonstrate that the presence of such induced insulating gaps leads to a characteristic atypical behavior of the critical supercurrent in Josephson junctions based on these hybrid structures. Our findings provide important insights for the design of robust quantum computing platforms utilizing hybrid superconductor-hole systems.

We propose a hybrid quantum device based on the graphene Josephson junctions, where the vibrational degrees of freedom of a graphene membrane couple to the superconducting circuits. The flexural mode-controlled tunneling of the Cooper pairs introduces a strong and tunable coupling even at the zero-point fluctuation level. By employing this interaction, we show that a parametric process can be efficiently implemented. We then investigate foundational and technological applications of our hybrid device empowered by nonlinear interactions, with fast generation of nonclassical mechanical states, and critically enhanced quantum sensing under suitable quantum control. Our work provides the possibility of employing the graphene motional degree of freedom for quantum information processing in circuit quantum nanomechanical structures.

Recently, the isolation of two-dimensional magnetic materials has opened several avenues for possible applications in spintronics. Among these materials, CrSBr has sparked interest due to its relatively high Curie temperature, highly anisotropic lattice structure, and high structural stability. These properties run along with others shared by any atomically thin material such as its outstanding deformation capacity and a strong optical response dominated by excitonic effects. The combination of these properties provides a fairly uncharted playground to explore the interplay between magnetism and optical excitations. Here, we focus our attention on the theoretical optical response of CrSBr under several distinct strain configurations, analyzing the resulting changes to both the excitonic peaks and overall shape of the diagonal components of the linear conductivity tensor.

We show that a three-state discrete-time quantum walk (DTQW) on a square lattice, with an SU(3) coin, realizes stroboscopic Floquet phases that host dispersive topological bound states in the continuum (TBICs). Time-independent step operations act as the periodic drive and map the one-step unitary to an effective Floquet Hamiltonian. Chern-number calculations resolve three quasienergy bands and their phase boundaries as the rotation angles are varied, and bulk-boundary correspondence in semi-infinite and fully finite geometries accounts for the edge spectra. At interfaces between media with the same bandwise Chern numbers but different coin parameters, nonchiral edge modes become embedded yet localized TBICs with tunable group velocity and selective excitation, while numerics indicate robustness to moderate coin disorder. Together with feasible routes in trapped-ion, cold-atom, and photonic platforms and an explicit decoherence model, these results identify DTQWs as a controllable setting for protected quantum-state transport and storage, relevant to quantum information and communication technologies.

Anyons are quasiparticles with fractional charge and statistics that arise in strongly correlated two-dimensional systems such as the fractional quantum Hall effect and fractional Chern insulators. Interactions between anyons can lead to emergent phenomena, such as anyon superconductivity as well as anyon condensation that allows for a hierarchical construction of quantum Hall states. In this work, we study how quasihole anyons in a $\nu =1/3$ Laughlin fractional quantum Hall state can be bound together by a sufficiently strong attractive impurity potential. The competition between the repulsive interaction between the quasiholes themselves and the attractive interaction between the quasiholes and the impurity leads to states with different numbers of quasiholes bound to the impurity. Tuning the chemical potential via gating while remaining within a quantum Hall plateau changes the number of quasiholes bound to the impurity. We propose methods for studying these states experimentally, for example, using scanning tunneling microscopy and exciton spectroscopy. While the impurities in traditional platforms such as GaAs heterostructures are typically too weak to observe the binding of anyons, the recently discovered zero-field fractional Chern insulators in twisted ${\mathrm{MoTe}}_2$ offer a platform that may realize the strong-impurity regime.

We report a giant enhancement of circular photogalvanic effect (CPGE) in the oxide two-dimensional electron gas at ${\mathrm{LaAlO}}_3/{\mathrm{SrTiO}}_3$ and $\mathrm{LaAl}{\mathrm{O}}_3/\mathrm{KTa}{\mathrm{O}}_3$ interfaces through the synergistic ultraviolet (UV) photoexcitation and electrostatic gating. The UV illumination generates high-density photocarriers by promoting valence-to-conduction band transitions, which simultaneously increase the Fermi wave vector $k_{\mathrm{F}}$ and Fermi energy $E_{\mathrm{F}}$. Concurrently, the gate-induced oxygen vacancy migration toward the interface amplifies the Rashba spin-orbit coupling coefficient ${\alpha }_{\mathrm{R}}$. Strikingly, the CPGE photocurrent exhibits a nonmonotonic dependence on both gate voltage and UV intensity, peaking at an optimal carrier density where $k_{\mathrm{F}}$ and ${\alpha }_{\mathrm{R}}$ cooperatively enhance the spin-momentum locking. This dual control strategy achieves a CPGE responsivity of 22.71 µV for $\mathrm{LaAl}{\mathrm{O}}_3/\mathrm{KTa}{\mathrm{O}}_3$ interfaces. Our findings establish the photoelectric coupling as a powerful knob for tailoring nonequilibrium spin phenomena in quantum oxide interfaces, with direct implications for reconfigurable spintronic devices.

Understanding the impact of gate errors on quantum circuits is crucial to determining the potential applications of quantum computers, especially in the absence of large-scale error-corrected hardware. We put forward analytical arguments, corroborated by extensive numerical and experimental evidence, that Trotterized quantum circuits simulating the time evolution of systems near thermal equilibrium are substantially more robust to both quantum gate errors and Trotter (discretization) errors than is widely assumed. In Quantinuum’s trapped-ion computers, the weakly entangling gates that appear in Trotterized circuits can be implemented natively, and their error rate is smaller when they generate less entanglement; from benchmarking, we know that the error for a gate $exp[-i(Z\otimes Z\left)\tau \right]$ decreases roughly linearly with $\tau$, up to a small offset at $\tau =0$. We provide extensive evidence that this scaling, together with the robustness of near-thermal dynamics to both gate and discretization errors, facilitates substantial improvements in the achievable accuracy of Trotterized dynamics on near-term quantum computers. We make heavy use of a theoretical tool—a statistical ensemble of random product states that approximates a thermal state, which can be efficiently prepared with low noise on quantum computers. We outline how the random product state ensemble can be used to predict, optimize, and design Hamiltonian simulation experiments on near-thermal quantum systems.

In the pursuit of robust quantum computing, we put forth a platform based on photonic qubits in a circuit-QED environment. Specifically, we propose a versatile two-qubit gate based on two cavities coupled via a transmon, constituting a selective number-dependent phase gate operating on the in-phase eigenmodes of the two cavities, the Eigen-SNAP gate. This gate natively operates in the dispersive coupling regime of the cavities and the transmon, and operates by driving the transmon externally, to imprint desired phases on the number states. As an example for the utility of the Eigen-SNAP gate, we implement a $\sqrt{\text{SWAP}}$ gate on a system of two logical bosonic qubits encoded in the cavities. Further, we use numerical optimization to determine the optimal implementation of the $\sqrt{\text{SWAP}}$. We find that the fidelities of these optimal protocols are only limited by the coherence times of the system's components. These findings pave the way to continuous-variable quantum computing in cavity-transmon systems.

We use the transfer tensor method to analyze localization and transport in simple disordered systems, specifically the Anderson and Aubry-André-Harper models. Emphasis is placed on the memory effects that emerge when ensemble-averaging over disorder, even when individual trajectories are strictly Markovian. We find that transfer tensor memory effects arise to remove fictitious terms that would correspond to redrawing static disorder at each time step, which would create a temporally uncorrelated dynamic disorder. Our results show that while eternal memory is a necessary condition for localization, it is not sufficient. We determine that signatures of localization and transport can be found within the transfer tensors themselves by defining a metric called “outgoing pseudoflux.” This work establishes connections between theoretical research on dynamical maps and Markovianity and localization phenomena in physically realizable model systems.

By applying density functional theory calculations, we study the electronic and magnetic properties of ${\mathrm{KFe}}_2{\mathrm{As}}_2$, which exhibits two superconducting domes under pressure. We find there are competing magnetic instabilities from itinerant electrons in both superconducting phases. The lower $T_c$ of the first superconducting phase at ambient pressure can be attributed to the competing instabilities at $(\pi ,0,\pi )$, which favor the double stripe type or plaquette antiferromagnetic order. The second superconducting phase is further suppressed by the competing ferromagnetic and stripe antiferromagnetic instabilities at higher pressure. In addition, we find that applying pressure acts as self-doping, leading to variations in instabilities from the itinerant electrons. Our results imply that the instability of the Pauli susceptibility from itinerant electrons is a possible quantity that describes the various characters of ${\mathrm{KFe}}_2{\mathrm{As}}_2$ under pressure and have important implications for understanding the pressure manipulation of superconductivity in iron-based superconductors.