Weak-value amplification (WVA), a postselection-based technique that amplifies weak physical signals by preparing nearly orthogonal pre- and postselected quantum states, is intrinsically limited by various kinds of technical noise, which distorts amplified weak values, especially when discarding photons in postselection. While prior work established the efficacy of autocorrelative weak-value amplification (AWVA) under Gaussian noise, practical implementations face challenges from band-limited laser-source noise and detection noise (including shot noise and electrical noise). Here, we demonstrate that the AWVA protocol robustly suppresses both laser-power fluctuations and detection noise. Numerical experiments in Simulink further reveal AWVA's dual advantage: under high-power conditions, the noise-reduction superiority of AWVA over WVA becomes in- creasingly pronounced as input laser power increases, whereas in detection-limited regimes AWVA achieves an order-of-magnitude lower uncertainty, closely approaching the Cramér-Rao bound. Crucially, this work demonstrates that AWVA improves precision in both high-power (laser-noise-dominated) and photon-starved (detector-noise-dominated) regimes, thereby bridging these operating extremes and advancing precision in applications from gravitational-wave detection to hybrid quantum systems.

It is known that ${\rho }^{AB}$ as a bipartite reduced state of the three-qubit Greenberger-Horne-Zeilinger (GHZ) state is separable, but part $A$ and part $B$ indeed “share tripartite entanglement” in the GHZ state. Namely, whether a state can “share” more entanglement is dependent on the global system it lives in. Here We explore such kind of entanglement in any $n$-partite system with arbitrary dimensions, $n⩾3$, and call it partitewise entanglement, which includes pairwise entanglement proposed by Dong et al. [Phys. Rev. A 110, 032420 (2024)] as a special case. We propose three classes of the partitewise entanglement measures, which are based on the genuine entanglement measure, the minimal bipartition, and the minimal distance from the partitewise separable states, respectively. The former two methods are far ranging since all of them are defined by the reduced function. [Note: If a positive function $h$ satisfies $h\left({\rho }^A\right)=E\left(\right|\psi \rangle \langle \psi {|}^{AB})$ for some bipartite entanglement measure $E, h$ is called the reduced function (of $E$).] Consequently, we establish the framework of the resource theory of the partitewise entanglement. In addition, we investigate the partitewise entanglement extensibility and give a measure of such extensibility, from which we find that the maximal partitewise entanglement extension is its purification. Lastly, the relation between this extensibility and the partitewise entanglement is discussed.

In this paper, we give the local distinguishability of four orthogonal product states (OPSs) on multipartite and high-dimension systems. To characterize the different orthogonal relationships between four multipartite OPSs, a new concept, i.e., the vector of the numbers of pairwise orthogonal relations, is proposed. We classify four tripartite OPSs, any two of which are orthogonal only on one subsystem, into three categories by using the vectors of the numbers of pairwise orthogonal relations. We prove that any four tripartite OPSs belonging to two of the three categories can be perfectly distinguished by local operations and classical communication (LOCC). Meanwhile, we find an interesting phenomenon that two sets of four tripartite OPSs belonging to the remaining one of the three categories have different local distinguishability even if they have the same orthogonal graph. This means that the orthogonal graph is not a sufficient condition for determining the local distinguishability of a set of OPSs. Additionally, for the remaining category, we specify the conditions under which four tripartite OPSs can be locally distinguished and the conditions under which four tripartite OPSs cannot be perfectly distinguished by LOCC. On the other hand, we prove that any four tripartite OPSs with seven or more pairwise orthogonal relations can be perfectly distinguished by LOCC. Furthermore, we prove that any four OPSs with six or more pairwise orthogonal relations can be perfectly distinguished by LOCC on four-, five-, and six-partite systems.

Quantum network protocols depend on the availability of shared entanglement. Given that entanglement generation and distribution are affected by noise, characterization of the shared entangled states is essential to bound the errors of the protocols. This work analyzes the estimation of Bell diagonal states within quantum networks, where operations are limited to local actions and classical communication. We demonstrate the advantages of Bayesian mean estimation over direct inversion and maximum-likelihood estimation, providing analytical expressions for estimation risk and supporting our findings with numerical simulations.

Oblivious transfer (OT) is an essential building block for secure multiparty computation. Up to now, one- and two-server OT protocols have been investigated. It has been proven that unconditionally secure one-server OT is impossible even with the quantum system. Recently, Hayashi and Song proposed the first two-server OT protocol for quantum messages [Adv. Quantum Technol. 7, 2300184 (2024)], which is the only one for two-server OT for quantum messages to our knowledge. This protocol has the assumption that two quantum servers do not communicate with each other. However, it is unrealistic to make such an assumption. In addition, an equation error occurs in the protocol description. To tackle these issues, we first point out the equation error existent in the protocol of Hayashi and Song and correct it. Then, we propose a two-server OT protocol for quantum messages by using entanglement swapping. Security analysis shows that the user privacy holds even if the two quantum servers communicate mutually.

There have been several reported values for the nuclear quadrupole moment of ${}^{43}\mathrm{Ca}$, but significant discrepancies exist among these reported values, ranging from $-0.0408\left(8\right)$ b to $-0.065\left(20\right)$ b. In this work we perform an accurate calculation of the electric-field gradients of the $4s4p{}^3{P}_1, 4s4p{}^3{P}_2$, and $4s3d{}^1{D}_2$ states in the ${}^{43}\mathrm{Ca}$ atom using a hybrid method. This hybrid method integrates the advantages of the configuration-interaction method and the coupled-cluster method and can simultaneously account for core-core, core-valence, and valence-valence correlations. By combining our calculated results with the experimental values of the electric quadrupole hyperfine-structure constants of these three states, an accurate and reliable nuclear quadrupole moment of ${}^{43}\mathrm{Ca}$ is determined to be $-0.0479\left(6\right)$ b, which could be recommended as a reference for ${}^{43}\mathrm{Ca}$.

Accurate photodissociation cross sections of beryllium monohydride (BeH) have been calculated for photon wavelengths ranging from 82 nm to the dissociation threshold, covering transitions from the ground state $1{}^2{\mathrm{\Sigma }}^{+}$ to excited electronic states up to $6{}^2{\mathrm{\Sigma }}^{+}$ and $5{}^2\mathrm{\Pi }$. Particular emphasis is placed on elucidating the nonadiabatic coupling between states $2{}^2{\mathrm{\Sigma }}^{+}$ and $3{}^2{\mathrm{\Sigma }}^{+}$, and its fundamental role in photodissociation dynamics. By explicitly incorporating these nonadiabatic effects into rovibrationally resolved cross sections calculated at various temperatures, we demonstrate how nonadiabatic couplings profoundly influence molecular fragmentation pathways. Our analysis reveals that such couplings induce numerous Feshbach resonances, significantly modifying both resonance positions and intensities in the computed cross sections. The physical origin of these resonances is interpreted in terms of coupling-induced trapping of continuum states by bound or quasibound rovibrational levels, highlighting the importance of rigorous nonadiabatic treatments for accurate predictions. This study presents the first comprehensive theoretical characterization of BeH photodissociation including nonadiabatic interactions, providing essential benchmark data for experimental verifications and astrophysical modeling, particularly relevant for understanding BeH photochemical processes in the early universe and ultraviolet-irradiated interstellar environments. The present framework provides a potentially instructive reference for future implementations of local nonadiabatic coupling in molecular photodissociation investigations.

A central challenge in strongly interacting many-body systems is understanding the far-from-equilibrium dynamics. Here we study the many-body magnetic dynamics of the two-component Bose-Hubbard model by developing a two-component extension of nonequilibrium bosonic dynamical mean-field theory. Using this numerical method, we uncover rich quantum spin dynamics via interspecies interaction quenches. A sudden ramp up of interactions induces slow thermalization, leading to a long-lived metastable state, whereas quenching to weak interactions results in rapid thermal equilibrium, featuring a two-step relaxation behavior through distinct exponential decays. Furthermore, under periodic modulation of the interspecies interactions, emergent Floquet dynamics drives a transition from a magnetic to an unordered phase.

We study the spatiotemporal dynamics of interacting bosons on a two-dimensional Hubbard lattice in the strongly interacting regime, taking into account the dynamics of condensate amplitude as well as the direct transport of noncondensed fluctuations. To that end we develop a self-consistent density-matrix approach which goes beyond the standard Gutzwiller mean-field theory. Starting from the Liouville-von-Neumann equation we derive a quantum master equation for the time evolution of the system's local density matrix at each lattice site, with a dynamical bath that represents the rest of the system. We apply this method to the expansion dynamics of an initially prepared cloud of interacting bosons in an optical lattice. We observe a ballistic expansion of the condensate, as expected, followed by slow, diffusive transport of the normal bosons. We discuss, in particular, the robustness of the Mott insulator phase as well as its melting due to incoherent transport. The method should be applicable to various models of lattice bosons in the strongly correlated regime.

An invisible pulsation soliton (IPS) is a novel type of soliton with an inconspicuous pulse energy fluctuation in contrast with a stable soliton. In this work, echoing previous investigations of IPS dynamics, such as the IP of soliton molecules, the IP of harmonic mode locking, and intermittent IP induced by temporal-gain dynamics, we report the experimental observation of IPS explosion dynamics in a mode-locked fiber laser. Three types of IPS explosion phenomena with different evolution characteristics are successively obtained, i.e., an ordinary IPS explosion, an IPS explosion accompanied by soliton splitting, and an IPS explosion induced by collision after soliton splitting. Our work provides complementary evidence for IPS as a metastable state, and might benefit the understanding of nonlinear soliton dynamics.

The ultrabroad spectrum of few-cycle and especially subcycle pulses requires multiple energy levels in a medium to be properly considered in order to describe the pulse propagation effects. In this paper we go beyond the standard two-level or related few-level approximations and theoretically analyze the propagation of subcycle pulses in a nonequilibrium multilevel resonant medium. We specifically address the case of pulse durations, smaller than the periods of resonant transitions in a medium, where the appropriate analytical models can be provided, and assume accordingly a slow dissipation in the medium. We demonstrate a number of nonlinear phenomena, arising under such conditions, in particular the formation of stable subcycle dissipative solitons of various profiles in a nonequilibrium medium, including superluminal ones, as well as study possible scenarios of their collision.

We give a simple argument that, for a large class of jump operators, the Lindblad evolution can be written as a gradient flow in the space of density operators acting on a Hilbert space of dimension $D$. We give explicit expressions for the (matrix-valued) eigenvectors and eigenvalues of the Lindblad evolution using this formalism. We argue that in many cases the interpretation of the evolution is simplified by passing from the complex $D^2$-dimensional space of density operators to the real $D^2-1$-dimensional space of Bloch vectors. When jump operators are non-Hermitian the evolution is not in general gradient flow, but we show that it nevertheless resembles gradient flow in two particular ways. Importantly, the steady states of Lindbladian evolution are still determined by the potential in all cases.

Quantum systems subjected to a continuous weak measurement process evolve according to stochastic differential equations. Depending on the outcomes of these stochastic measurements, the quantum state may diffuse in various directions across the state space. This note points out that, in many scenarios relevant to quantum engineering, this diffusion is effectively constrained to a low-dimensional space. Specifically, the quantum state remains confined to a low-dimensional, nonlinear manifold—often time-dependent, yet independent of the specific measurement outcomes. This note derives the corresponding low-dimensional formulations for expressing the stochastically evolving state in several prototypical cases: quantum nondemolition measurements in arbitrary dimensions; quadrature measurements of a harmonic oscillator (linear quantum system); and measurements of subsystems within multipartite quantum systems. Additionally, it introduces an algebraic criterion to determine whether such low-dimensional manifolds exist or persist when additional dynamics are present.

We use the spin-boson model to describe the dynamics of a two-level atom interacting with Fabry-Pérot cavity modes. We solve the Schrödinger equation for the system-bath model without the Born-Markov approximation to derive the non-Markovian reduced dynamics of the qubit. We further construct an exact Lindblad-type master equation for it. Similar to the quantum Otto cycle, we construct a non-Markovian quasicyclic process based on the atom-cavity interactions, which we call the quasi-Otto cycle. For judicious choices of input state and parameters, the quasicycle can be more efficient as a quantum engine than the Otto cycle. We also show that if the quasicycle is repeated multiple times, the efficiency of the quasi-Otto engine asymptotically approaches that of the Otto engine.

We investigate magnon-magnon entanglement and synchronization in a cavity-magnon system comprising two yttrium iron garnet spheres, focusing on the role of symmetric and asymmetric magnon pairs under varying physical parameters, including cavity detuning, photon-magnon coupling, dissipation rates, and thermal noise. Our results demonstrate that symmetric magnon pairs generally favor the generation of both quantum entanglement and synchronization, with enhanced resilience to thermal fluctuations compared to asymmetric configurations. Particularly, the quantum entanglement and synchronization obtained in both scenarios (symmetric and asymmetric magnon pairs) can exhibit vastly different behaviors with changes in some physical factors. Further, we explore the interplay between magnon-magnon quantum entanglement and synchronization. We identify a competitive relationship between entanglement and synchronization in certain situations, manifesting as parameter-dependent complementarity where enhancement of one effect correlates with suppression of the other. This study underscores the critical influence of symmetry configuration on quantum correlations in hybrid cavity-magnon systems, offering theoretical guidance for optimizing entanglement and synchronization in quantum information platforms.

In recent years, squeezed-cat codes with resilience to specific types of loss have been proposed as a step toward realizing fault-tolerant optical quantum computers. However, error correction for squeezed-cat codes requires a strong nonlinearity, which makes its implementation challenging with current technology. We propose a novel hybrid code that combines the squeezed-cat code and the polarization qubit. First, we propose a generation method and a universal gate set that can be implemented with a linear optical system. Then we show the superiority of the hybrid squeezed-cat code over the hybrid cat code and the squeezed-cat code through numerical simulations. These results demonstrate that the hybrid squeezed-cat code is a promising candidate as a new resource for optical quantum information processing.

Lechner-Hauke-Zoller (LHZ) parity embedding is one of the front-running methods for implementing difficult-to-engineer long-range interactions in quantum optimization problems. Continuous-time quantum walks are a leading approach for solving quantum optimization problems. Because they populate excited states, quantum walks can avoid the exponential gap-closing problems seen in other continuous-time techniques such as quantum annealing and adiabatic quantum computation. An important question, therefore, is how continuous-time quantum walks perform in combination with the LHZ parity embedding. By numerically simulating continuous-time quantum walks on four-, five-, and six-logical-qubit Sherrington-Kirkpatrick Ising spin glass instances embedded onto the LHZ parity embedding, we are able to verify the continued efficacy of heuristics used to estimate the optimal hopping rate and the numerical agreement with the theory behind the location of the lower bound of the LHZ parity constraint strength. In addition, by comparing several different LHZ-based decoding methods, we identified postreadout error correction techniques which improve the success probability of the quantum walk.

We present a theoretical study of dynamic interference (DI) in laser-assisted photoemission (LAPE), a regime widely employed in attosecond and few-femtosecond spectroscopy. Using the strong-field approximation (SFA) and a Floquet framework, we analyze the influence of a finite infrared (IR) pulse envelope under experimentally relevant conditions. In addition to the established phase modulation mechanism—referred to as laser-assisted dynamic interference (LADI)—we identify an alternative source of DI arising from a time-dependent amplitude modulation, which we term dynamic multiphoton interference (DMPI). We attribute DMPI to quantum-path interference among competing multiphoton transitions, which, depending on the exact employed parameters, can overshadow LADI when electrons are emitted along the IR polarization axis. We further delineate the conditions necessary for the clear experimental observation of both effects and assess their robustness against variations in pump pulse intensity in a realistic experimental condition.

We investigate the ground-state and finite-temperature phase diagrams of the Bose-Hubbard model on a honeycomb superlattice. The interplay between the superlattice potential depth $\mathrm{\Delta }/t$ and the on-site interaction $U/t$ gives rise to three distinct quantum phases at zero temperature: a superfluid phase, a Mott insulator I phase with unit filling on each site, and a Mott insulator II phase characterized by density imbalance—double occupancy on one sublattice and vacancy on the other at unit filling. The SF-MI transitions are found to be continuous, consistent with second-order quantum phase transitions. We further extend our analysis to finite temperatures within the superfluid regime. Our work highlights how a honeycomb superlattice geometry enables access to interaction- and lattice-modulation-driven quantum phases, including a density-imbalanced Mott insulator and a robust superfluid regime, offering concrete theoretical predictions for cold-atom experiments.