The experimental detection of nonequilibrium quantum criticality remains a challenge, as traditional signatures like dynamical quantum phase transitions rely on hard-to-measure global properties. Here, we demonstrate that local connected correlation functions provide an alternative, practical means to directly probe the dynamics of magnetic order in a quenched Rydberg-atom array. Using a Magnus expansion formalism, we derive analytic expressions for these correlations that capture a smooth crossover from antiferromagnetic to ferromagnetic dominance. Our analytic results, which reveal the critical parameter relationship $U_c\left(\delta \right)$, are validated against exact numerical simulations and exhibit robustness to finite-size effects. By shifting the focus from global singularities to local correlations, our protocol establishes a direct and feasible path to observe the rich critical dynamics in scalable quantum simulators.

In this work, we compute the out-of-time-ordered correlator (OTOC) for canonical position and momentum operators across a hierarchy of non-Hermitian oscillator models: the exactly solvable Swanson Hamiltonian, its Kerr-nonlinear extension, and parametrically driven variants. By employing the biorthogonal formalism required for parity-time symmetric quantum mechanics, we evaluate OTOCs both at zero and finite temperature, distinguishing behavior in the unbroken (real-spectrum) and broken (complex-spectrum) phases. Our analysis reveals how integrability, nonlinearity, driving, and parity-time symmetry breaking shape the temporal growth of operator correlations—providing a clear benchmark for OTOC dynamics in non-Hermitian quadratic and weakly anharmonic systems. We further characterize critical scaling of the OTOC near the exceptional point and discuss experimental perspectives for observing these effects in photonic, circuit-QED, and trapped-ion platforms.

Unextendible product bases (UPBs) are central to the study of local distinguishability of orthogonal product states. While their connection to quantum nonlocality via Bell inequalities is well established, their link to quantum contextuality remains largely unexplored. We establish a graph theoretic connection between contextuality and UPBs. First, an equivalence between Klyachko-Can-Binicioğlu-Shumovsky (KCBS) vectors and the Pyramid UPB is shown and then by constructing a one parameter family of UPB vectors, a quantitative connection between the contextuality strength and bound entanglement of states associated with the corresponding UPB is demonstrated. This equivalence is extended to generalized KCBS vectors and the generalized pyramid (GenPyramid) UPB. Another class of minimal UPBs in ${\mathbb{C}}^3\otimes {\mathbb{C}}^n$ is constructed using Lovász-optimal orthogonal representations (LOORs) of cycle graphs and their complements which we term the GenContextual UPB. Any minimal UPB in this dimension is shown to be graph-equivalent to the GenContextual UPB. We briefly discuss the distinguishability properties of GenContextual UPB. In the reverse direction, we observe that the constituent vectors of the QuadRes UPB are LOORs of Paley graphs. The structural properties of these graphs make them suitable candidates for constructing noncontextuality inequalities, thereby establishing a bidirectional connection between quantum contextuality and UPBs.

We propose a distillation-free scheme for the fault‐tolerant implementation of non-Clifford gates at the logical level, thereby completing the universal gate set. Our approach exploits generalized lattice surgery to integrate two quantum error-correcting (QEC) codes. Specifically, non-Clifford gates are executed transversally on one QEC code and then teleported to the main circuit via a logical-level joint measurement that connects two distinct QEC codes. In contrast to conventional magic state distillation (MSD) combined with gate teleportation, our method obviates the need for concatenating separate codes for distillation and logical qubits, thus reducing the total overhead from multiplicative to additive scaling. We illustrate our approach by explicitly demonstrating its implementation for a three-dimensional color code interfaced with a surface code of the same code distance, and comment on its potential advantage over the conventional MSD-teleportation scheme.

We present high-precision quantum computing simulations of three-body atoms (He and ${\mathrm{H}}^{-}$) and molecules $({\mathrm{H}}_2{}^{+} \text{and} {\mathrm{HD}}^{+})$, the latter being studied beyond the Born-Oppenheimer approximation. The noniterative disentangled unitary coupled-cluster variational quantum eigensolver (NI-DUCC-VQE) [M. Haidar et al., Quantum Sci. Technol. 10, 025031 (2025)] is used. By combining a first-quantized Hamiltonian with a minimal complete pool of Lie algebraic excitations, we construct a compact Ansatz with a gradient-independent construction, avoiding costly gradient evaluations and yielding efficient computational scaling with both basis size and electron number. It enables rapid convergence, and no barren plateaus are observed in the tested systems. Energy errors as low as ${10}^{-11}$ a.u. with state fidelities only limited by arithmetic precision are achieved in only a few thousand function evaluations in all four systems. These results make three-body atoms and molecules excellent candidates for benchmarking and testing on current noisy intermediate-scale quantum devices. Further, our approach can be extended to more complex systems with larger basis sets, taking advantage of the efficient scaling of qubit requirements to study electronic correlations and nonadiabatic effects with high precision. We also demonstrate the applicability of NI-DUCC-VQE for simulating higher-order effects such as relativistic corrections and hyperfine interactions.

Quantum systems with more than two levels, known as qudits, offer enhanced information density and potentially more efficient quantum operations compared with traditional qubits. Among the various physical platforms under investigation, single-molecule magnets (SMMs) stand out due to their intrinsic magnetic anisotropy, long spin-relaxation times, and the natural presence of multiple accessible spin states. In this work, we explore two distinct control strategies for implementing state-to-state transitions within the multilevel structure of SMMs, viz., a resonant magnetic-field manipulation ($\pi$-pulse control) and the so-called quantum Zermelo navigation approach, which provides the time-optimal Hamiltonian that transforms a given initial state to a given target state. We present a comparative analysis of these two methods, evaluating their operational efficiency and feasibility for experimental realization. Our results show that, while $\pi$-pulse control is limited by strict timing constraints, the Zermelo method faces significant challenges in terms of its physical implementation.

Rapid development of quantum computing technology has led to a wide variety of sophisticated quantum devices. Benchmarking these systems becomes crucial for understanding their capabilities and paving the way for future advancements. The Quantum Volume (QV) test is one of the most widely used benchmarks for evaluating quantum computer performance due to its architecture independence. However, as the number of qubits in a quantum device grows, the test faces a significant limitation. It requires determining the subspace of the most probable outcomes, a task that is typically performed via classical simulation of the quantum circuit and therefore incurs an exponential computational cost. In this work, we propose modifications to the QV test, by adopting a carefully restricted circuit ensemble generated from a gate set that remains universal for quantum computation, that allow for the direct determination of the heavy-output subspace. Crucially, the modified circuits remain capable of general quantum computation. This approach overcomes the scalability barrier of the QV test beyond classical computational limits, while still probing the key features of universal quantum computing.

Identification of cancer driver genes is fundamental for the development of targeted therapeutic interventions. The integration of mutational profiles with protein-protein-interaction (PPI) networks offers a promising avenue for their detection [Horn et al., Nat. Methods 15, 61 (2018); Nourbakhsh et al., Briefings Bioinform. 25, bbad519 (2024)], but scaling to large network datasets is computationally demanding. Quantum computing offers compact representations and potential complexity reductions. Motivated by the classical method of Gumpinger et al. [Bioinformatics 36, i508 (2020)], in this work we introduce a supervised quantum framework that combines mutation scores with network topology via a state-preparation scheme we call quantum multiorder moment embedding (QMME). QMME encodes low-order statistical moments over the mutation scores of a node's immediate and second-order neighbors and encodes this information into quantum states. These states are used as inputs to a kernel-based quantum binary classifier that discriminates known driver genes from others. Simulations on an empirical PPI network demonstrate competitive performance, with a 12.6% recall gain over a classical baseline. The pipeline performs explicit quantum state preparation and requires no classical training, enabling an efficient, nearly end-to-end quantum workflow. A brief complexity analysis suggests the approach could achieve a quantum speedup in network-based cancer-gene prediction. This work underscores the potential of supervised quantum-graph-learning frameworks to advance biological discovery.

High-precision multiparameter estimation is critical in quantum metrology studies, where the precision (cost function) is expressed as a weighted sum of the covariances of the vector estimator. It necessitates the preparation of different input states to achieve optimal precision with varying weighted matrices. In this article, we propose to prepare a highly adjustable weighted three-mode cat state (WTCS) with a triple-well condensate system, then apply it to realize Heisenberg-level two-parameter estimation. The parameters are encoded with the ground-state energy imbalance between the three wells, estimated with the data acquired via particle number measurement after a proper rotation. Significantly, by manipulating the strength and asymmetry of the interwell hopping, we can fine-tune the WTCS prepared according to the weights adopted in defining the cost function. As a result, the precision of this two-parameter estimation scheme achieves the Heisenberg level consistently. We expect this scheme to be utilized in estimating vector parameters such as the magnetic fields.

In this work, we investigate the convergence and physical reliability of truncated-basis representations in solid-state high-order harmonic generation by comparing the stationary Bloch and accelerated Bloch bases. We show that the two representations exhibit intrinsic numerical inequivalence under strong-field driving, leading to distinct carrier dynamics and harmonic emission. Consistent with previous studies, the convergence behaviors of the two bases with respect to the number of retained bands differ qualitatively, with the accelerated Bloch basis achieving reliable spectral convergence using significantly fewer bands. By analyzing the deviation between truncated-band and full-band results, we show that the energetically remote bands affect the harmonic generation through two distinct mechanisms: the population leakage into other bands, which mainly leads to intensity renormalization, and the modifications of the interband polarization phase within the truncated subspace, which cause structural distortions of the spectrum. These multiband effects can be systematically incorporated into reduced two-band descriptions through a band-folding correction. Our results provide a physically transparent procedure for assessing truncated-basis convergence and offer practical guidance for efficient reduced-basis modeling of strong-field electron dynamics in crystalline solids.

Ionization by a sequence of extreme ultraviolet pulses is investigated based on the rigorous numerical solution of the time-dependent Schrödinger equation, when the driving laser field is treated exactly. This goes beyond the typically used first-order nondipole approximation and reveals the effects of radiation pressure to its full extent. Specifically, we observe the comb structures in the angle-resolved energy distributions of photoelectrons. The comb peaks are shifted, however, depending on the electron emission angle. While a similar effect has already been observed in the first-order nondipole approximation, upon increasing the laser field strength the discrepancy with our exact results becomes more pronounced. Also, we observe the additional substructure of the comb peaks arising in the energy distributions of photoelectrons. Finally, as our numerical calculations account for the atomic potential in the entire interaction region, we observe the loss of coherence of comb structures upon increasing the number of laser pulses, which we attribute to rescattering.

Deterministic generation of tailored subcycle optical waveforms—from unipolar to multipeak structures—remains a challenge in ultrafast science. We propose an approach based on space-time field transformation via structured plasma mirrors. It is shown that tailored plasma density profiles can produce customizable subcycle optical waveforms—from rectangular to multipeak profiles—via direct spatial-to-temporal mapping. The underlying single-atom dynamics are validated by three-dimensional time-dependent Schrödinger equation simulations. A scaling relation $\tau =2L/c$ is established, linking the spatial period $L$ of the density modulation to the temporal separation $\tau$ between waveform features. This relation may be viewed as a temporal analog of Bragg diffraction. The methodology provides a route to optical field control in attosecond science and petahertz electronics, where spatial material structure directly influences temporal light structure. The extension of this approach to solid-state platforms, including composition-modulated superlattices, is briefly discussed.

The spin dynamics of two alkali-metal atoms in an optical tweezer is driven by spin-changing collisions that couple the spin state of the atoms to their relative motion. This paper experimentally studies the resulting spin states when the relative motion is in a thermal state with $k_{B}T$ much larger than the energies of the spin states that take part in the dynamics. We find that an initially unentangled spin state can evolve into an entangled state. This is contrary to the common case when coupling a quantum system to hot degrees of freedom leads to loss of entanglement and not its generation. Moreover, we show that the generated entanglement is technologically useful as it, in principle, can enhance the sensitivity of measurements beyond the standard quantum limit. This may provide a promising avenue for robust entanglement generation for future technologies.

The issue of separating Schrödinger-type quantum time evolution into a product of holonomic and dynamical parts in the nonadiabatic non-Abelian case is examined. We identify all special cases in which this kind of separation is possible, and we prove that separability is a gauge-invariant property of quantum time evolution. The general analysis is implemented in a three-level system with $\mathrm{\Lambda }$-type coupling structures. The typical case where the holonomic and dynamical parts do not separate is illustrated by means of two noncommuting $\mathrm{\Lambda }$-type Hamiltonians.

We investigate the limits of epistemic models in reproducing the empirical predictions of general quantum preparations. This involves comparing the common quantum overlap determined by the antidistinguishability of a set of preparations with the common epistemic overlap of the probability distribution over the ontic states describing these preparations. We show that no epistemic model with nonzero common overlap can reproduce the predictions of quantum theory for mixed preparations, even for qubit systems. We explicitly provide sets of distinct mixed preparations, starting from qutrit systems, that give rise to identical quantum mixed states for which the common epistemic overlap must be zero. Finally, we demonstrate the strongest form of preparation contextuality by presenting pairs of mixed preparations that yield identical quantum mixed states while their epistemic overlap must vanish.

Bit commitment is a fundamental cryptographic primitive and a cornerstone for numerous two-party cryptographic protocols, including zero-knowledge proofs. However, it has been proven that unconditionally secure bit commitment, both classical and quantum, is impossible. In this work, we demonstrate that imposing a restriction on the committing party to perform only separable operations enables secure quantum bit-commitment schemes. Specifically, we prove that in any perfectly hiding bit-commitment protocol, an honestly committing party limited to separable operations will be detected with high probability if they attempt to alter their commitment. To illustrate our findings, we present an example protocol.

Quantum phase transitions in many-body systems are fundamentally characterized by complex-correlation structures, which pose computational challenges for conventional methods in large systems. To address this, we propose a hybrid quantum-classical model inspired by quantum transformer attention mechanisms. This model employs a swap-test-based correlation, together with a parameterized quantum circuit, to perform ground-state classification. Benchmarked on the cluster-Ising model with system sizes of 9 and 15 qubits, the model achieves high classification accuracy with less than 100 training data points and demonstrates robustness against variations in the training set. Further analysis reveals that the model successfully captures phase-sensitive features and characteristic physical length scales, offering a scalable and data-efficient approach for quantum phase recognition in complex many-body systems.