Motivated by the recent experimental observation of dipolar supersolid stripes in a quasi-two-dimensional geometry [arXiv:2512.13280], we study a trapped system of fully polarized dipoles in a strongly axially confined geometry, at both zero and finite temperatures, by means of Bogoliubov theory. The dipoles are strongly harmonically trapped along the $z$ axis and subjected to a box trap in the $x\text{−}y$ plane. We characterize the physics of the trapped system at zero and finite temperatures as a function of the tilting angle of the dipoles, the number of particles, and the scattering length, restricting ourselves to the experimentally relevant regime of large condensate fractions. We also illustrate the influence of the aspect ratio of the box trap in the liquid character of the system and its structure. We observe a remarkable promotion of spatial modulations when temperature is increased while keeping the total particle number constant for specific configurations, in qualitative agreement with previous Monte Carlo results in a three-dimensional geometry. Our results are useful to understand the zero-temperature physics of the trapped dipolar system in the quasi-two-dimensional limit and in the strongly dipolar regime. In addition, they allow us to assess the effect of temperature in its equilibrium properties in experimentally relevant conditions, which may be useful for thermometry applications.

Nonlinear frequency down-conversion, particularly difference frequency generation (DFG) between near-infrared (NIR) pulses, is the predominant method for generating midinfrared (MIR) pulsed lasers in the $3-5\mu \mathrm{m}$ range via the idler wave. However, this approach suffers from inherently low conversion efficiency. The wavelength-dependent Manley-Rowe relations impose a fundamental limit on the maximum extractable power of the MIR idler from a given pump. Here, we propose a dual-DFG-OPA (optical parametric amplification) scheme that substantially enhances MIR idler conversion efficiency through synchronized parametric energy recycling. The signal wave, which carries the majority of the pump energy during DFG, is simultaneously reused as a secondary pump to drive optical parametric amplification of the MIR idler. Using a standard single-period periodically poled lithium niobate crystal, we theoretically demonstrate the dynamics and parametric gain control of this synchronized process based on a representative $3.6\mu \mathrm{m}$ DFG configuration pumped by 800 and 1030 nm pulsed lasers. Beyond improved pump energy utilization, the controlled, synchronous depletion of the signal wave mitigates the intrinsic back-conversion effect in parametric processes. Compared to conventional single-stage DFG, the dual-DFG-OPA architecture yields a twofold increase in output power of the $3.6\mu \mathrm{m}$ MIR idler wave.

In structured electromagnetic fields, polarization textures are often closely linked to the spatial variation of the energy flow. However, this familiar picture has been established mainly for lossless and isotropic settings, and concrete examples showing how it is modified in media with gain and loss remain limited. Here, we demonstrate that optical skin modes associated with the non-Hermitian skin effect carry a finite transverse circular-polarization texture, characterized by the third Stokes parameter as a descriptor of the local in-plane electric-field rotation. We further show that this electric-field spin texture deviates from the familiar lossless spin-flow picture. Using exact transverse electric mode solutions, we separate the common exponential skin envelope from the oscillatory component. This decomposition shows that the circular-polarization texture is not generated by the skin envelope itself but by the oscillatory interference component modified by non-Hermiticity. It also reveals a handedness bias and a reshaped spatial relation between circularity and intensity. Finite-element calculations confirm that these features remain robust in loss-biased anisotropic media. These results show that gain and loss provide additional freedom for engineering electric-field spin textures beyond conventional lossless photonic settings.

Continuous-variable (CV) quantum teleportation is usually benchmarked by average fidelity, but when the teleportation is repeatedly used within optical networks or measurement-based architectures, uniformity across the input ensemble becomes equally important. We analyze this issue using two complementary figures of merit: the average fidelity and the fidelity deviation, which quantifies the input dependence of the input-conditioned, outcome-averaged teleportation fidelity. We prove that any deterministic unity-gain teleportation channel that is displacement covariant has vanishing fidelity deviation for coherent-state benchmarking, irrespective of whether the shared entangled resource is Gaussian or non-Gaussian. Nonzero deviation therefore diagnoses covariance breaking rather than non-Gaussianity. For a small nonuniform deformation away from a covariant baseline, we derive a local, protocol-dependent relation between the fidelity gain and the induced deviation; this relation is not a universal lower bound on probabilistic or non-Gaussian enhancements. As a concrete example, we study a measurement-based noiseless linear amplification inspired hard-window record-filtering surrogate. Within this model, the resulting trade-off among average fidelity, fidelity deviation, and success probability shows that stronger filtering can improve the conditional fidelity by concentrating the successful events in favored regions of phase space, thereby suppressing the success probability and reducing input uniformity. We further distinguish fidelity nonuniformity, quantified by $D$, from heralding selectivity, quantified by the input dependence of the success probability. Our results provide an operational framework for distinguishing genuine channel improvement from selectivity-driven postselected advantage and suggest that the probabilistic CV teleportation should be assessed with average quality, universality, and heralding rate treated on an equal footing.

We propose a scheme to engineer the superradiant phase transition (SPT) in cavity magnonics by periodically modulating the frequency of the magnon mode. The studied system is composed of a yttrium iron garnet (YIG) sphere positioned inside a microwave cavity, where magnons in the YIG sphere are strongly coupled to microwave photons. Under the Floquet drive, the effective frequencies of both the cavity and magnon modes can be readily controlled via the frequency and strength of the Floquet field. This tunability allows the cavity magnonic system to support a rich steady-state phase diagram, featuring parity-symmetric, parity-symmetry-broken, bistable, and unstable phases. With the increase of Floquet-field strength, the system exhibits a discontinuous phase transition from the parity-symmetric phase to the parity-symmetry-broken phase at a critical threshold, accompanied by an abrupt jump of the magnon occupation from zero to a finite value. Upon further increase of Floquet-field strength, the magnon occupation declines continuously from a nonzero value back to zero, corresponding to a second-order phase transition that restores the parity-symmetric phase. Additionally, fluctuations in magnon number during the SPT process are examined. Our work establishes an alternative route to engineer the cavity-magnon SPT without relying on the microwave parametric drive.

We consider the amplification of bosonic interactions through parametric control that implements squeezing along orthogonal quadratures. We show that bosonic interactions described by certain classes of quadratic and quartic Hamiltonians can be enhanced in this way while simultaneously overcoming noise and decoherence. In general, the amplification method enhances both desired and undesired interactions present in the system. Depending on the case, however, detrimental processes can be less amplified than the desired couplings. We leverage this observation to improve the fidelity for preparing Bell-type entangled states between two bosonic modes in the presence of noise and losses. We also investigate noise models for which the protocol either fails or partially achieves a noise-tolerant state-preparation speedup. Our work facilitates faster preparation of complex quantum states and implementation of entangling gates in the presence of decoherence mechanisms.

We investigate the dynamics of a $\mathrm{\Lambda }$-type giant atom (GA) whose two transitions are coupled to the guided modes of a one-dimensional waveguide at two spatially separated points, with the GA initially excited and the electromagnetic modes of the waveguide in vacuum. The spontaneous emission properties of this GA are investigated by solving the delay-differential equation for the amplitude of the three-level GA in its excited state. Signatures of non-Markovian behavior manifest in the population trapping in the excited state of the GA in the regime where the distance $d$ of the coupling points is smaller than or comparable to the coherent length $L$ characterizing the width of the emitted wave packet. And an exact Markovian dynamics is also found when $d\ge L$ via the inference from adjusting the energy spacing and the inherent time delay in addition to the complex phases in the atom-light coupling, matching the behavior of a small atom coupled to a waveguide.

We propose ultrafast all-optical switching exploiting the bistability between a spatially uniform photon superfluid and a spontaneously ordered supersolid in a driven-dissipative microcavity. The key ingredient is a tunable nonlocal photon-photon interaction engineered by embedding a high-mobility two-dimensional electron gas (2DEG) inside the cavity. A drift current displaces the Fermi disk, imparting a negative region to the Lindhard interaction kernel at finite wave vectors and triggering a roton instability. The resulting bistable $S$-curve supports a write-hold-erase protocol in which short optical pulses toggle the system between branches with a switching contrast of order 120 dB in our simulations. The hysteretic on state persists under a constant subthreshold drive after the write pulse is removed, realizing an all-optical bistable memory. Since the photon field couples additively to each embedded quantum well, stacking layers with distinct drift angles allows the roton profile to be engineered with higher-order symmetries, imprinting richer spatial order on the supersolid and enabling nonbinary generalizations of the switch. Operating in the ultrafast, sub-fJ regime, this platform outperforms most existing all-optical switches in contrast and reconfigurability.

Quantizing a single, spinless, nonrelativistic particle constrained to a moving surface, and requiring that Schrödinger's equation is recovered, implies that the surface should be advected by the Madelung velocity field. Moreover, the surface-height gradient, weighted by the squared modulus of the wave function, should have zero net outward flux across closed paths. These constraints determine a phase-coincident companion solution to Schrödinger's equation, which allows us to construct an orthogonal unoccupied state. By supposing that surface fluctuations may induce rare transitions into this state, we motivate an empirical test of de Broglie's double-solution theory. The associated Fermi-golden-rule rate is obtained from first-order perturbation theory in the fluctuation amplitude.

To uncover the mechanism behind dynamical quantum phase transitions (DQPTs), we employ initial-state engineering by tuning the effective inverse temperature $\beta$ of the coherent Gibbs state in the one-dimensional XY model. We find that DQPTs arising from interphase quenches are topologically protected, originating from the topological mismatch between the initial state and the postquench Hamiltonian, whereas those triggered by intraphase quenches are topologically independent. Despite this distinction, both types of DQPTs are governed by a unified geometric condition: A DQPT occurs when the Bloch vector of a given momentum mode becomes orthogonal to the postquench Hamiltonian axis, causing the mode-resolved Loschmidt amplitude to vanish at critical times. We show that the effective inverse temperature $\beta$ of the coherent Gibbs state acts as a geometric knob that continuously rotates the initial Bloch vector. For interphase quenches, the topological mismatch guarantees this orthogonality for any $\beta$, making topological protection a natural consequence of this geometric picture. For intraphase quenches, the orthogonality condition reveals a particularly insightful limit: at $\beta =0$, DQPTs can occur even without any quench; as $\beta$ increases, the initial Bloch vector rotates smoothly, and this rotation must be compensated for by a corresponding rotation of the Hamiltonian axis, precisely achieved by the external quench. This interplay gives rise to two critical modes that emerge from opposite Brillouin-zone boundaries, migrate inward with increasing $\beta$, and eventually coalesce and annihilate at a finite critical inverse temperature. These results establish a unified geometric description of DQPTs and elucidate how intraphase critical modes can arise and persist in the absence of any topological protection.

Quantum Fisher information (QFI) provides powerful entanglement criteria, but existing formulations are all related to the global QFI of the full composite state. We first define the block-diagonal postmeasurement ensemble obtained by local projective measurements on one subsystem of a bipartite state. Then we show that the QFI of the block-diagonal postmeasurement ensemble can decompose into the QFI of the unmeasured subsystem and the classical Fisher information of the measurement outcomes. For separable states the sum of the subsystem QFI and the classical Fisher information admits an upper bound expressed solely in terms of local variances; violation of this bound signals entanglement. Compared with Tóth's global spin-squeezing criterion [Phys. Rev. A 85, 022322 (2012)], our witness detects entanglement over a wider parameter range for high-dimensional systems. The dimensional advantage and reduced experimental cost make the subsystem QFI a practical entanglement witness.

Phase sensing with entangled multiqubit states in the presence of noise is a central theme of modern quantum metrology. The present work investigates Dicke-state superposition probes for quantum phase sensing under parameter encoding generated by one- and two-body interaction Hamiltonians. Under linear collective-spin encoding, near-optimal Dicke superposition states are shown to exhibit significantly enhanced robustness against phase damping noise compared with Greenberger-Horne-Zeilinger (GHZ), $W$-superposition, and balanced Dicke states, while maintaining favorable metrological performance under realistic decoherence channels. For two-body interactions, optimal probe states maximizing the quantum Fisher information are identified. Their noise resilience and metrological scaling behavior under phase damping, amplitude damping, and global depolarizing channels are analyzed. The associated near-optimal Dicke superposition states are found to exhibit improved resilience to phase damping for the system sizes considered. These results establish tailored near-optimal Dicke-state superposition probes as versatile and noise-resilient resources for Heisenberg and super-Heisenberg quantum phase sensing governed by one- and two-body interactions.

Quantum measurements inevitably disturb the state being measured and this disturbance, together with measurement incompatibility, plays a crucial role in the sequential sharing of nonlocality. While the information-disturbance trade-off for a single measurement is well understood, its interplay with measurement incompatibility remains relatively unexplored. Here, we investigate this interplay in the sequential sharing of three forms of tripartite nonlocality: standard, genuine, and no-signaling genuine. By deriving incompatibility trade-off relations among the measurements performed by the three observers, we show that the role of measurement incompatibility differs qualitatively across three forms of nonlocality. Standard tripartite nonlocality can be demonstrated even when one party performs compatible measurements, rendering unbounded sequential sharing essentially trivial. In contrast, genuine tripartite nonlocality cannot be realized when any two parties perform nearly compatible measurements, precluding unbounded sharing. For no-signaling–genuine nonlocality, however, the incompatibility trade-off allows the critical measurement unsharpness to be arbitrarily small, along with another party's measurement to be almost compatible, so that the minimum measurement-induced disturbance required to demonstrate nonlocality can also be made arbitrarily small, preserving sufficient quantum correlations for unbounded sequential sharing. We further show that in this regime, the feasibility of unbounded sequential sharing depends sensitively on the Kraus realization implementing the measurement. Our results demonstrate that measurement incompatibility alone does not fully determine the limits of sequential multipartite nonlocality; instead, the minimum measurement-induced disturbance required to achieve nonlocality plays an equally decisive operational role.

Quantum state transfer between distant nodes is essential for distributed quantum information processing. Existing protocols are typically optimized for specific coupling regimes, such as adiabatic dark-state transfer in the single-mode limit and pitch-and-catch schemes in the multimode regime, leaving the crossover between them without a simple and unified control strategy. Here, we identify a minimal two-parameter control framework that enables high-fidelity quantum state transfer across this single-mode–to–multimode crossover in a multimode quantum channel. Using a pulse-shaped pitch-and-catch protocol controlled only by the pulse ramp rate and the emission-absorption delay, we achieve transfer fidelities exceeding $99.9\%$, extending pitch-and-catch protocols toward the single-mode limit without requiring dark-state protection or complex pulse design. We further demonstrate robustness against dissipation, disorder, detuning, and imperfect initialization under experimentally realistic conditions. These results provide a simple and broadly applicable framework for state transfer in multimode quantum channels, with relevance to circuit-QED and hybrid quantum-acoustic systems.

Hybrid entanglement between discrete-variable (DV) and continuous-variable (CV) optical qubits is a fascinating area of quantum science and technology, because such hybrid entanglement is a key resource for building hybrid quantum networks and interconnecting quantum processors employing different qubit encodings. In this work, we propose a scheme to create a hybrid Greenberger-Horne-Zeilinger–type (GHZ-type) entangled state of a single DV optical qubit and $n$ CV optical qubits, utilizing $(n+1)$ microwave cavities coupled to a superconducting flux qutrit. The two logic states of a DV optical qubit here are represented by the vacuum state and the single-photon state of a cavity, while the two logic states of a CV optical qubit are indicated by the two coherent states of a cavity. The GHZ state preparation protocol requires only a few basic operations, significantly reducing circuit resources by utilizing a single flux qutrit as the coupler. Since the third energy level of the qutrit remains unpopulated during the operation, decoherence from higher levels is significantly suppressed. Moreover, the total operation time is independent of the number of microwave cavities, and the GHZ state is deterministically generated since no measurement is made. As an example, our numerical simulation demonstrates that high-fidelity generation of a hybrid four-cavity GHZ state is feasible with present circuit quantum electrodynamics (QED) technology. This proposal is quite universal and can be applied to other physical systems, such as microwave or optical cavities, which are coupled to an artificial or a natural atom.

We theoretically propose a scheme to achieve multisideband phonon blockade in a modulated circuit quantum acoustodynamics system, in which a high-overtone bulk acoustic-wave resonator is piezoelectrically coupled to a transmon qubit. By periodically modulating the qubit frequency, we theoretically demonstrate a Floquet-engineered Jaynes-Cummings interaction that can extend the conventional blockade condition from single-phonon resonance to multisideband resonance in the strong-coupling regime. Under weak-driving conditions, we first show the phonon blockade at the zeroth-order sideband due to the strong anharmonicity of the dressed-state energy levels and characterize the blockade performance by combining the second-order correlation function $g^{\left(2\right)}\left(0\right)$ and the single-phonon population $P_1$. Crucially, it is revealed that the detuning between the phonon mode and the qubit can lead to a trade-off between $g^{\left(2\right)}\left(0\right)$ and $P_1$ by altering the dressed-state energy-level structure and composition and thus can be used to manipulate the purity and brightness of the single-phonon source. Then we extend the phonon blockade to multiple tunable Floquet sidebands and analyze the influence of the system parameters on the phonon blockade. The proposed scheme enables the manipulation of the phonon blockade at multiple distinct frequencies without modifying the intrinsic system parameters, which reduces the experimental complexity and improves the operational flexibility, thereby facilitating the potential applications of circuit quantum acoustodynamics systems in emerging quantum technologies.

We consider the generation of photonic graph states in a linear optics setting where sequential nondeterministic fusion measurements are used to build large graph states out of small linear clusters and develop a framework to optimize the building process using graph-theoretic characterizations of fusion networks. We present graph-state generation protocols for linear cluster resource states and type-I/type-II fusions which are adaptive to fusion failure, that is, they reuse leftover graph states in the remaining building process. To estimate hardware costs, we interpret our protocols as finite Markov processes. This viewpoint allows us to cast the expected number of fusion measurements until success as a first passage problem. We then deploy a pipeline of polynomial algorithms to optimize arbitrary graph states, extract fusion networks, and find beneficial orderings of fusions. We check the effectiveness of these algorithms by verifying that the corresponding mean first passage times are decreased. We evaluate our pipeline for different initial resource states and fusion mechanisms with varying success probabilities. Results show reductions in the fusion overhead by several orders of magnitude when compared to simple repeat until success protocols and by up to $40\%$ when compared to state-of-the-art graph-state generation protocols, especially for realistic fusion success probabilities between 50% and 75%.

We investigate the dissociative ionization of 1,3-butadiene (${\mathrm{C}}_4{\mathrm{H}}_6$) induced by 1-MeV/u ${\mathrm{C}}^{4+}$ ions using a cold-target recoil-ion momentum spectroscopy, with a specific focus on the three-body channels involving ${\mathrm{H}}_2{}^{+}$ formation. With triplet-ion coincidence measurement, the dissociation channels ${{\mathrm{H}}_2}^{+} + {\mathrm{CH}}_2{}^{+} + {\mathrm{C}}_3{\mathrm{H}}_2{}^{+}$ and ${\mathrm{H}}_2{}^{+} + {\mathrm{CH}}_3{}^{+} + {\mathrm{C}}_3{\mathrm{H}}^{+}$ are directly identified, whereas the ${{\mathrm{H}}_2}^{+} + {\mathrm{C}}_2{\mathrm{H}}^{+} + {\mathrm{C}}_2{\mathrm{H}}_3{}^{+}$ and ${{\mathrm{H}}_2}^{+} + {\mathrm{C}}_2{{\mathrm{H}}_2}^{+} + {\mathrm{C}}_2{\mathrm{H}}_2{}^{+}$ channels are not well separated in the time-of-flight correlation map. These two three-body channels are disentangled by analyzing the correlation between kinetic energy release versus dissociation angle. Using Dalitz plots, Newton diagrams, and the native frame method, the sequential pathways with ${\mathrm{H}}_2{}^{+}$ emitted first are identified for all four channels. In addition, the ${{\mathrm{H}}_2}^{+} + {\mathrm{CH}}_2{}^{+} + {\mathrm{C}}_3{{\mathrm{H}}_2}^{+}$ channel exhibits a sequential pathway with ${\mathrm{CH}}_2{}^{+}$ emitted first, whereas the ${\mathrm{H}}_2{}^{+} + {\mathrm{C}}_2\mathrm{H}{}^{+} + {\mathrm{C}}_2{\mathrm{H}}_3{}^{+}$ channel also proceeds via a concerted mechanism. $Ab initio$ potential-energy surface calculations are performed to illuminate the intrinsic state and hydrogen-site selectivity governing ${\mathrm{H}}_2{}^{+}$ formation. These results provide insight into the mechanisms and dynamics of ${\mathrm{H}}_2{}^{+}$ formation in the three-body fragmentation processes of hydrocarbon molecules.

We present measurements on a metastable state in ${\mathrm{Th}}^{2+}$ with the electronic configuration $6d^2{}^{3}P_0\left(5090{\mathrm{cm}}^{-1}\right)$. This is motivated by the prospect of using the state in laser excitation of the low-energy ${}^{229}\mathrm{Th}$ nuclear resonance independent from the leading hyperfine interactions. The $6d^2{}^{3}P_0$ state has no dipole-allowed radiative decay channel and is connected to the second ground state $6d^2{}^3{F}_2\left(63{\mathrm{cm}}^{-1}\right)$ through an electric quadrupole transition only. We populate the state by laser excitation at 484 nm via a higher excited level and detect its population in laser-induced fluorescence. The isotope shift of the $J=0$ level between ${}^{232}\mathrm{Th}^{2+}$ and ${}^{229}\mathrm{Th}^{2+}$ is determined as a measure of the interaction of electronic and nuclear charge distributions. The lifetime of the level in our ion trap with buffer gas is limited by collisional mixing with the nearby state $5f6d{}^{3}G_3\left(5060{\mathrm{cm}}^{-1}\right)$. In ultrahigh vacuum, it could serve as a hyperfine-free nuclear clock that is largely immune to field-induced frequency shifts via the electron shell.

Purely quantum phenomena such as dynamical localization (DL) can be observed in a molecular rotor subjected to a periodic train of short and intense laser pulses in the gas phase. Using requantized classical molecular dynamics simulations, we investigate the impact of collisional effects for ${\mathrm{O}}_2$ molecules. We consider different trains of kicks for which the system exhibits quantum resonance, DL, or Bloch oscillations under collision-free conditions. Within achievable experimental conditions, we demonstrate that, as the gas pressure increases, all the dynamics become progressively similar, leading to a quantum-to-classical transition. We study how decoherence induced by intermolecular collisions reduces the quantum interferences through loss of memory. These findings pave the way for future experimental investigations and further theoretical studies of the influence of dissipation on quantum effects in rotational dynamics.