Electrostatically tunable quantum confinement in nanoscale systems offers unprecedented opportunities for manipulating artificial quantum matter, positioning these platforms at the frontier of quantum science. The strategic integration of distinct confinement mechanisms could revolutionize quantum functionality by enabling novel states with enhanced coherence properties. Here, we demonstrate inherently interfacial potential engineering by combining lateral semiconductor 2D moiré potentials with vertical quantum confinement effects in semimetal bismuth nanofilms, creating localized periodic sites for quantum-confined charges. Using scanning tunneling microscopy, we observe moiré-mediated Wigner crystals with self-organized electron lattices arising from strong Coulomb interactions, exhibiting unexplored multiple energy quantization behaviors that can be manipulated by quantum well states in ultrathin bismuth films. These precisely localizable charge states provide a promising platform for van der Waals (vdW) charge qubits electrostatically confined within 2D materials. Our work demonstrates extended tunability of artificial atom states in phase, space, and energy regimes. With optimized designs, these 2D vdW architectures bridge fundamental Wigner crystallization phenomena with practical applications in advanced electronic systems and quantum state manipulation.

Quantum Encryption in Phase Space (QEPS) is a physical-layer encryption framework that harnesses the quantum-mechanical properties of coherent states to secure optical communications against both classical and quantum computational threats. By applying randomized phase shifts, displacements, or their dynamic combinations—implemented as unitary transformations in phase space—QEPS disrupts the phase reference essential for coherent detection, establishing aphase synchronization barrier. This review synthesizes the theoretical foundations, security mechanisms, and experimental progress of the QEPS framework, encompassing its three principal variants: the round-trip Quantum Public Key Envelope (QPKE) protocol—a public-key-like scheme built upon phase randomization (QEPS-p), the symmetric phase-only QEPS-p, and the displacement-based QEPS-d. Experimental validations demonstrate that authorized users achieve bit-error rates (BERs) below the forward-error-correction threshold, whereas eavesdroppers are confined to BERs near 50%, equivalent to random guessing—all while utilizing standard coherent optical transceivers at data rates up to 200 Gb/s over 80 km of fiber. We further examine QEPS’s robustness to channel impairments, its seamless compatibility with existing digital signal processing (DSP) pipelines, and its distinctive position within the post-quantum cryptography landscape. Finally, we outline key challenges and future research directions toward deploying QEPS as a practical, quantum-resistant security layer for next-generation optical networks.

Abstract The SU(1,1) interferometer, a nonlinear analog of the traditional Mach-Zehnder interferometer, has emerged as a powerful tool for achieving phase sensitivity beyond the standard quantum limit. In this work, we propose the use of a superposition of even and odd coherent states as input state to enhance the phase sensitivity of an SU(1,1) interferometer. These non-classical states exhibit unique properties such as squeezing, entanglement, and quantum interference, which can be harnessed to improve metrological precision. Phase sensitivity is analyzed using single-intensity detection and homodyne detection schemes under both ideal and photon loss cases, which demonstrates significant improvements over classical and squeezed-vacuum inputs. In addition, we evaluate the quantum Cramér-Rao lower bound by employing the quantum Fisher information formalism, showing that it surpasses the standard quantum limit and approaches the Heisenberg limit under optimal conditions. Our results highlight the potential of the even and odd coherent states superposition in quantum metrology and provide a pathway for achieving ultra-precise phase measurements in SU(1,1) interferometers for applications in optical sensing, and quantum information processing.

Quantum state discrimination plays a central role in quantum information and communication. For the discrimination of optical quantum states, the two most widely adopted measurement techniques are photon detection, which produces discrete outcomes, and homodyne detection, which produces continuous outcomes. While various protocols using photon detection have been proposed for optimal and near-optimal discrimination between two coherent states, homodyne detection is known to have higher error rates, with its minimum achievable error rate often referred to as the Gaussian limit. In this work, we demonstrate that, despite the fundamental differences between discretely labelled and continuously labelled measurements, continuously labelled non-Gaussian measurements can also achieve near-optimal coherent state discrimination. We design two discrimination protocols that surpass the Gaussian limit: one using non-Gaussian unitary operations with homodyne detection, and another based on orthogonal polynomials. Our results show that photon detection is not required for near-optimal coherent state discrimination and that we can achieve error rates close to the Helstrom bound at low energies with continuously labelled measurements. We also find that our schemes maintain an advantage over the photon detection-based Kennedy receiver for a moderate range of coherent state amplitudes.

Abstract Random walks in a finite Abelian group G are studied. They use Markov chains with doubly stochastic transition matrices, in a Birkhoff subpolytope B ( G ) associated with the group G . It is shown that all future probability vectors belong to a polytope which does not depend on the transition matrices, and which shrinks during time evolution. Various quantities are used to describe the probability vectors: the majorization preorder, Lorenz values and the Gini index, entropic quantities, and the total variation distance. The general results are applied to the additive group Z ( d ) , and to the Heisenberg–Weyl group H W ( d ) / Z ( d ) . A physical implementation of random walks in Z ( d ) that involves a sequence of non-selective projective measurements, is discussed. A physical implementation of random walks in the Heisenberg–Weyl group H W ( d ) / Z ( d ) using a sequence of non-selective positive operator-valued measure measurements with coherent states, is also presented.

Superconductivity has been a vigorously researched topic since its discovery in 1911. Raising the superconducting transition temperature (Tc) has been the main driving force behind such long-sustained efforts due to its potential for impacting humanity and the fundamental knowledge gained from understanding this macroscopic coherent quantum state at high temperatures. The successful development of high-Tc superconductivity will make possible extraordinarily efficient generation, delivery, and utilization of energy and could also enable the development of controlled fusion while impacting other burgeoning fields like quantum computation and quantum electronics. However, progress has been hindered by a longstanding plateau in the record ambient-pressure Tc, unchanged since 1993. Subsequent significant advancements in Tc have been achieved only under high pressures, preventing the realization of superconductivity's full potential. To directly address this challenge, we developed a pressure-quench protocol (PQP) to stabilize pressure-induced/-enhanced superconducting states at ambient pressure. Here, we achieve a record ambient-pressure Tc of 151 K in the cuprate HgBa2Ca2Cu3O8+δ via PQP. The experimental results are further supported by synchrotron X-ray diffraction measurements and phonon and electronic structure calculations. This breakthrough opens avenues for stabilizing and exploring ambient-pressure high-Tc superconducting states and other quantum states that have been previously only accessible under pressure, paving the way for deeper understanding and practical applications of high-Tc superconductivity and beyond.

We systematically investigate the multiplicity of flow states in centrifugal convection in water at about $40\,^\circ$ C with Prandtl number $Pr = 4.3$ in a vertically aligned annulus in which the inner radius, the gap between the cylinders and the height all coincide (6 cm). This leaves two independent control parameters: the thermal driving, quantified by the Rayleigh number ${\textit{Ra}}$ , and the rotation strength, expressed by the Froude number ${\textit{Fr}}$ . We explore the range $2\times 10^{5} \le {{\textit{Ra}}} \le 10^{7}$ for ${{\textit{Fr}}} = 10$ and $100$ with direct numerical simulations (DNS). The states are characterised by the number of convection rolls in the mid-height cross-section. We show that the final state sensitively depends on the initial condition, leading to pronounced multistability and substantial variations in heat and momentum transport, while the range of attainable states is strongly restricted. We derive a theoretical estimate of the admissible roll numbers based on the Poincaré–Friedrichs inequality and demonstrate quantitative agreement with the DNS. We further show that, for larger ${\textit{Ra}}$ , the range of possible states shrinks systematically due to an elliptical instability, providing a predictive framework for the selection and disappearance of coherent roll states in centrifugal convection.

We introduce the , a nonperiodic analog of the discrete time crystal that arises in periodically driven dissipative quantum many-body systems. This phase is defined by two key features: (1) spatial long-range order arising from the spontaneous breaking of an internal symmetry and (2) temporally chaotic oscillations of the order parameter, whose lifetime diverges with system size. In other words, a time glass is a state of matter in which all components evolve in a synchronized yet chaotic manner. To characterize the time glass phase, we focus on the spectral gap of the one-cycle (Floquet) Liouvillian, which determines the decay rate of the slowest relaxation mode. Theoretical arguments and numerical studies of periodically driven dissipative Ising models show that, in the time glass phase, the Liouvillian gap remains finite in the thermodynamic limit, in contrast to time crystals where the gap closes exponentially with system size. We further demonstrate that the Liouvillian gap converges to the decay rate of the order-parameter autocorrelation derived from the classical (mean-field) dynamics in the thermodynamic limit. This result establishes a direct correspondence between microscopic spectral features and emergent macroscopic dynamics in driven dissipative quantum systems. At first glance, the existence of a nonzero Liouvillian gap appears incompatible with the presence of indefinitely persistent chaotic oscillations. We resolve this apparent paradox by showing that the quantum Rényi divergence between a localized coherent initial state and the highly delocalized steady state grows unboundedly with system size. This divergence allows long-lived transients to persist even in the presence of a finite Liouvillian gap.

Quantitative control and measurement of quantum entanglement are essential for advancing quantum technologies. Photoionization induced by ultrashort laser pulses provides a unique platform for studying entanglement between photoelectrons and residual ions, representing one of the most intriguing quantum phenomena in attosecond physics. Although extensive studies have focused on the coherence properties within either the emitted electrons or the ions individually, the electron-ion entanglement has remained largely unexplored. In this work, we bridge this gap by investigating the resonance-enhanced multiphoton ionization of argon atoms driven by two time-delayed ultrashort ultraviolet pulses. Employing state-of-the-art first-principles multi-electron simulations, we demonstrate the ability to reconstruct and precisely manipulate the purity of electron quantum states through detailed analysis of the photoelectron angular distributions. Our results reveal distinct scattering-phase differences among various electron configurations within the same partial wave channel, providing unequivocal evidence of electron-ion correlation and entanglement. With the fast development of free-electron lasers, this study establishes an experimentally feasible framework for directly controlling quantum entanglement in ultrafast ionization processes, offering new insights and powerful methodologies for exploring complex electron dynamics in many-electron systems.

Abstract We theoretically propose a protocol for coherent quantum state control in a short periodically driven Rydberg atom array. This Floquet engineering effectively suppresses the Rabi coupling and further reshapes Rydberg-Rydberg interactions, enabling precise control of Rydberg dynamics including population trapping and blockade dynamics. This capability permits the coherent manipulation of targeted quantum states, such as population-trapping ground state and entangled states with single or double excitations. A key finding is the robustness of these dynamics against variations in the Rydberg atom interaction, allowing for reliable control even in weak interaction regimes. Floquet spectral analysis further reveals that the stability–and eventual breakdown–of the frozen ground state is fundamentally governed by the splitting, convergence, and spacing of quasienergy levels. Moreover, a systematic analysis of parameter dependence identifies precise operational ranges for quantum state control. These results establish a practical framework for Floquet-engineered quantum manipulation, with promising prospects for quantum information processing applications.

Abstract The precision of quantum measurements can be effectively improved by using both photon-added non-Gaussian operations and Kerr nonlinear phase shift. Here, we employ a coherent state mixed with a photon-added squeezed vacuum state as the input to a Mach–Zehnder interferometer with parity detection, thereby achieving a significant enhancement in phase measurement precision. Our research focuses on the phase sensitivity of linear phase shift under both ideal conditions and photon loss, as well as quantum Fisher information (QFI). The results demonstrate that employing the photon addition operations can markedly enhance phase sensitivity and QFI, and under optimal conditions, the measurement precision can approach the Heisenberg limit for the linear phase shift case. In addition, we delve deeper into the scenario of replacing the linear phase shift with a Kerr nonlinear one and systematically analyze the QFI under both ideal and photon loss conditions. By comparison, it is evident that employing both the photon addition operations and the Kerr nonlinear phase shift can further significantly enhance phase measurement precision while effectively improving the system’s robustness against photon loss. These findings are instrumental in facilitating the development and practical application of quantum metrology.

We calculate and plot 2D slices of the Wigner functions of several families of highly excited even and odd superpositions of nonlinear coherent states, looking for conditions under which such superpositions can be interpreted as models of the “Schrödinger cat” states. The decisive factor seems to be the form of the number distribution function over the Fock basis: it must have well localized peaks. Otherwise, no “cat-like” structures are observed.

Aided by quantum sources, quantum metrology helps enhance measurement precision. Here, we construct a theoretical model for quantum imaging based on squeezed states and present the corresponding numerical results. Through discretization and quantum Fisher information theory, we investigate the two-point resolution and spatial multi-parameter estimation of optical fields with unknown spatial distributions. We calculate and compare imaging results based on squeezed vacuum states, coherent states, and squeezed coherent states; our results show that squeezed coherent states yield greater quantum Fisher information, which can effectively improve imaging quality. In addition, we analyze the influence of imaging basis functions, degree of squeezing, quantum correlations, and other factors on imaging performance. The proposed quantum imaging model and computational method can be extended to more complex scenarios, such as multi-mode squeezed-state imaging schemes and incoherent imaging systems. In the future, this approach is expected to find applications in practical imaging systems, including Raman microscopy and stimulated Brillouin scattering imaging.

Time relates to actualization, which is physically interpreted as a quantum measurement. The measurement has a dual structure consisting of the reality being measured (externality) and the reality by which the measurement takes place (an agent or ontolon). These two constituents refer to the two types of time: physical time measured by clocks, and internal time, defined by Bergson as la durée (duration). The latter holds the coherent internal quantum state of entangled potentialities, while the former represents the collapse of this state, thereby flowing through quantum transactions. This view unifies the Everett (Many-worlds) and the Copenhagen (Wave function collapse) interpretations of the quantum measurement. Time as a duration can be estimated via the energy-time uncertainty relation, which links the precision of the measurement result to the value of energy dissipation during it and to its span. The precision of the measurement result enables the process of quantum computation, which emerges in the systems characterized by internal closure, i.e., autopoietic (living) systems operating at the state of sustainable non-equilibrium. Energy dissipation in the process of measurement occurs as the emission of quanta that trigger the collapse of the coherent entangled state. These quanta are recognized in the system, enabling the performance of higher-level control over elementary computational actions through their integration within the complex system. It is concluded that the energy-time uncertainty relation represents the fundamental internal quantum constraint of natural computation, the process that spans from enzymatic catalysis to complex regulatory and adaptive activities, and finally to reflexive consciousness.

Abstract We investigate quantum sensing for spectroscopy in a system consisting of a two-level atom coupled to a continuum of modes. We focus on optimizing the pulse shape of a coherent state to maximize the quantum Fisher information (QFI) of the emitted light with the aim of estimating the atom’s dipole moment, which is proportional to its spontaneous emission rate. To achieve this, we derive a set of coupled differential equations, which include the standard optical Bloch equations as a subset and whose solution directly yields the QFI of the emitted light without resorting to finite-difference methods. Furthermore, we analyze the factors that govern its optimization, provide analytic solutions in both the long and the short pulse width limits, and examine the role of the average photon number of the pulses. We then show that under the closed (periodic) boundary conditions, the harmonic (plane-wave) with frequency equal to half the spontaneous emission rate and a phase determined by detuning are optimal in the long pulse width limit. We further show numerically that photodetection saturates the classical Fisher information.

ABSTRACT Strong‐field ionization by thermal light is studied. Even though thermal light can be considered as completely classical stochastic light, it can also be treated as quantum light in the sense that it can be represented by a superposition of coherent states, similarly as has been done for the bright squeezed vacuum light, for example. Such a distribution over coherent states contains components with an intensity much higher than the average intensity of the thermal light. This increases the ionization probability by many orders of magnitude. For low intensities, in the multiphoton regime, the enhancement is by the factor of , with the multiphoton order of the process. This result is in agreement with an old experiment [ Phys. Rev. Lett . 32 (1974): 265] in which a similar enhancement factor appears if a multimode laser pulse is used instead of a single‐mode pulse. It is also shown that the plateau length in high‐order above‐threshold ionization by thermal light is extended by an order of magnitude in comparison with that of coherent laser light with the same average intensity.

Gustatory cortical (GC) and basolateral amygdalar (BLA) taste responses consist of an inter-regionally coherent three-part state sequence. This coherence suggests that reciprocal BLA-GC connectivity is important for taste processing, but it remains unknown 1) whether BLA-GC coherence actually reflects a reciprocal "conversation" (as opposed to one region simply driving the other); and 2) whether such a "conversation" has anything to do with the taste processing observed within GC response dynamics. Here, we address these questions using network and single-neuron analysis of simultaneously recorded GC and BLA taste responses in awake rats. We find asymmetric, reciprocal µ-frequency influences that reflect taste processing dynamics: BLA→GC influence dominates between 300 and 1,000 ms (the epoch in which BLA codes palatability); afterward, when GC responses become palatability-related, and GC has been shown to release a behavior-relevant signal, the direction of influence reverses, becoming GC→BLA. Follow-up analyses demonstrate that this "turn-taking" exists alongside effectively synchronous amygdala-cortical coupling-the two regions functioning as a unified structure. Finally, to assess the implications of these interactions for single-neuron responses, we tested the response properties of GC neurons categorized by their inferred connectivity with BLA. GC neurons influenced by BLA produce stronger taste-specific and palatability-related responses than other GC neurons, and the strongest taste encoding is specifically found in GC neurons that both influence and receive influence from BLA-those most deeply embedded in the reciprocal circuit. These results, consistent with findings in multiple systems, support the novel conclusion that taste processing and decision-making is a function of the amygdala-cortical loop.NEW & NOTEWORTHY Conventionally, taste circuitry is considered feedforward, traveling up from the brainstem, with each additional node containing more sophisticated information. We challenge this convention by demonstrating that amygdala and cortex instead influence each other bidirectionally, yet in a direction-specific and asymmetric manner. These influences appear to drive different parts of the taste response, with distinct patterns for decision-making and behavioral output; furthermore, involvement in cortex-amygdala functional connectivity determines the strength of encoding in cortical single neurons.

Abstract Fluorescent nanodiamonds (FNDs) containing negatively charged nitrogen-vacancy (NV − ) centers are vital for many emerging quantum sensing applications from magnetometry to intracellular sensing in biology. However, developing a scalable fabrication method for FNDs hosting color centers with consistent bulk-like photoluminescence (PL) and spin coherence properties remains a highly desired but unrealized goal. Here, we investigate optimized ball milling of single-crystal diamonds produced via chemical vapor deposition (CVD) and containing 2 ppm of substitutional nitrogen and 0.3 ppm of NV − to achieve this goal. The NV charge state, PL lifetime, and spin properties of bulk CVD diamond samples are directly compared to milled CVD FNDs and commercial high-pressure high-temperature (HPHT) FNDs. We find that on average, the relative contribution of the NV − charge state to the total NV PL is lower and the NV PL lifetime is longer in CVD FNDs compared to HPHT FNDs, both likely due to the lower N s 0 concentration in CVD FNDs. The CVD bulk and CVD FNDs on average show similar average T 1 spin relaxation times of 3.2 ± 0.7 ms and 4.7 ± 1.6 ms, respectively, compared to 0.17 ± 0.01 ms for commercial HPHT FNDs. Our results demonstrate that ball milling of CVD diamonds enables the large-scale fabrication of NV ensembles in FNDs with bulk-like T 1 spin relaxation properties.

Random lasers (RLs) differ fundamentally from conventional lasers by replacing engineered optical cavities with disorder-mediated multiple scattering feedback, enabling cavity-free emission through photon interactions in disordered gain media. RLs have demonstrated many application potentials in the domains of optics and optoelectronics because of their low coherence, multidirectionality, and multiple wavelengths. However, the principle and procedure of RL generation, as well as the method for achieving low-threshold emission, still present difficulties. This study demonstrates the replica symmetry breaking (RSB) in coherent RL systems utilizing Enteromorpha prolifera (EP), a marine bio-scatterer exhibiting multiscale photonic architecture. The transition from the photon paramagnetic phase to the spin glass phase is seen with the increase of the pump energy in this random liquid phase system. The multiscale structure of EP enables efficient dye adsorption while enhancing photon scattering to amplify optical feedback, thereby achieving stable coherent random lasing with a low threshold. Power Fourier transform analysis was employed to calculate the effective optical cavity length of the RL system, depicting the coherent lasing dynamics and determining the free spectral range. The bio-enabled RL system demonstrated remarkable spatial coherence control with good speckle-free imaging potentials through quantitative analysis of speckle contrast and derived mode numbers, revealing pump-energy-dependent correlations that elucidate intermodal interaction dynamics. These findings advance the fundamental understanding of disordered photonic systems while establishing a sustainable framework for engineering bio-derived RL sources with tailored coherence properties.

Standard protocols in optical communication systems employ coherent states of light as the information carriers. The quantum nature inherent to these states introduces a fundamental complexity into the decoding process. In particular, when dealing with attenuated signals, the overlap between different states precludes the possibility of perfectly discriminate them. In this study, we investigate the performance of conventional and nonconventional quantum discrimination strategies under different informational metrics. We focus our analysis on binary coherent states within the ideal case of a lossless channel. The usual homodyne receiver was studied in comparison with the Kennedy and the optimized displacement receiver. We find that nonconventional strategies employing non-Gaussian measurements surpass the conventional homodyne discrimination scheme according to measurement error probability and mutual information.