Nonlocality serves as a fundamental quantum resource with essential applications in information processing tasks. All-versus-nothing (AVN) tests provide the strongest demonstration of quantum-classical conflicts without statistical loopholes. We demonstrate AVN nonlocality in cyclic quantum networks with multiple observers, revealing an elegant logical structure that enables violations with certainty. These AVN paradoxes are reformulated as Hardy-type arguments achieving unit probability, providing a powerful framework for network nonlocality certification. Remarkably, by assuming global noncontextual deterministic value assignments, the proof of our approach can be reformulated as a Kochen-Specker type contradiction in a state-independent fashion, establishing fundamental constraints on hidden-variable theories. These results provide a scalable certification method for multipartite nonlocality in quantum networks and enable novel quantum information protocols in network architectures beyond bipartite systems, paving the way for distributed quantum computing and communication applications.

As a key component of quantum networks, the quantum router distributes quantum information among different quantum nodes. The silicon-vacancy (SiV) center in diamond offers a promising platform for quantum technology due to its strong strain-induced coupling with phonons. However, the development of a practical quantum router faces the challenges of achieving long-range entanglement and suppressing decoherence. Here, we propose a non-Markovian quantum router based on a diamond waveguide embedded with an array of SiV centers as the quantum nodes. Unlike conventional channel-switching methods, our design enables parallel quantum-state transfer from a single input node to multiple target nodes, analogous to a classical WiFi router. We demonstrate that persistent entanglement and suppressed decoherence of the SiV centers over long distances are achievable when bound states are present in the energy spectrum of the total system formed by the SiV centers and the phonon waveguide. Our scheme enriches the implementation of quantum routing and prompts the development of solid-state quantum networks.

Quantum information processing relies on unitary operations to control quantum evolution, whose distinguishability reveals the fundamental differences between quantum processes. In principle, global strategies can realize optimal discrimination, but they remain impractical in distributed systems limited to local operations and classical communication (LOCC). Li et al. [Phys. Rev. A 96, 052327 (2017)] pointed out that an LOCC strategy can achieve the same optimal distinguishability as global strategies with a single query. In this study, we experimentally demonstrate LOCC-based discrimination of two-qubit entangling unitary operations on a programmable silicon photonic chip in the single-query setting, covering three representative cases: perfect, minimum-error, and unambiguous discrimination. Our results demonstrate that the LOCC strategy alone is sufficient to optimally discriminate any pair of two-qubit unitary operations, yielding a discrimination capability comparable to that of global strategies. For the nonperfectly distinguishable cases, error-free discrimination was realized through positive operator-valued measure (POVM) measurements, albeit with reduced efficiency. The experimentally demonstrated method for discriminating entangling unitary operations offers potential applications in quantum authentication and distributed quantum computing.

We discuss the behavior of general Floquet time crystals (FTCs), including prethermal ones, in closed systems acting as ac sensors. We provide an analytical treatment of their quantum Fisher information (QFI) dynamics, which characterizes the ultimate sensor accuracy. By tuning the direction and frequency of the ac field, we show how to induce transitions resonantly between macroscopic paired cat states in the FTC sensor. This allows for robust Heisenberg scaling precision (QFI approximately equal to $N^2{t}^2$) for exponentially long times in the system size. Moreover, the QFI dynamics exhibits a characteristic steplike structure in time due to the eventual dephasing along the cat subspaces. The behavior is discussed for various initial sensor preparations, including ground states and low- and high-correlated states. Furthermore, we examine the performance of the sensor along the FTC phase transition, with the QFI capturing its critical exponents. Our findings are presented for both linear and nonlinear response regimes and illustrated for a specific FTC based on the long-range interacting Lipkin-Meshkov-Glick model.

Photoelectron holographic (PH) interference is one of the research frontiers in strong-field physics, especially in forward- and backward-scattering holography. Achieving control over the specific type of hologram—whether forward- or backward-scattering dominated—has, however, remained challenging. In this study, we demonstrate that the photoelectron momentum distribution (PMD) of $H_2$ molecules in parallel linearly polarized laser pulses can be precisely controlled by tuning the amplitude ratio $\beta$ between the fundamental and second-harmonic (SH) pulses. We show that varying $\beta$ steers the dynamics from dominant forward scattering to backward scattering, transforming the interference pattern from a right-pointing spiderlike structure to a fishbonelike structure on both sides. A key finding is the emergence of a distinct specklelike structure within the fishbonelike structure at $\beta =-0.07$. Through quantum-trajectory analysis, we identify that these speckles originate from intercycle interference between electron wave packets released in adjacent optical cycles. This provides a clear signature to identify the role of long-term coherent accumulation in holographic structures. Our results not only provide a practical method to selectively generate desired holograms—e.g., backward-scattering holography for $\beta$ between 0 and $-0.15$—but also open a window to observe subcycle and multicycle interference effects in strong-field ionization.

The possibility of generating spectral combs of petahertz bandwidth is demonstrated from amplified spontaneous emission (ASE) of a collisional plasma-based x-ray laser when its active medium is irradiated with a linearly polarized near-infrared (IR) laser field. It is shown that at a sufficiently high IR-field intensity these combs correspond to a sequence of subfemtosecond beats of extreme ultraviolet (XUV) radiation of a deterministic shape. At the same time, at a lower IR-field intensity ASE remains quasimonochromatic, but its frequency shifts as a result of the IR-field-induced quadratic Stark effect. In this case, the frequency tuning range of XUV radiation is approximately twice the frequency of the modulating IR field. In addition, modulation by the IR field leads to amplitude and frequency discrimination of the polarization components of ASE, parallel and orthogonal to the IR field. The possibility of observing these effects is analyzed for a collisional plasma x-ray laser based on neon-like $\mathrm{T}{\mathrm{i}}^{12+}$ ions with an unperturbed ASE wavelength of 32.6 nm and a modulating field with a wavelength of 1 μm and an intensity in the range of ${10}^{16}\text{–}{10}^{17}\mathrm{W}/\mathrm{c}{\mathrm{m}}^2$.

In quantum censorship, an agency oversees quantum communication in a public-domain network. The agency restricts the users' communication to the free states of a quantum resource theory. Despite quantum correlations being fragile, any realistic censorship leaves behind some quantumness, raising concerns that censorship may be overcome through revival or distillation of quantum resources. Here, we introduce censorship protocols that do not require a perfect erasure of a quantum resource, but rather deem censorship successful if users are unable to restore the original quantum state using free operations. We investigate under which conditions censorship is secure, and when it might fail. Moreover, we address the issue of account sharing in quantum networks, wherein independent parties assist in transmitting quantum resources to censored users. This connects resource censorship to timely topics such as quantum catalysis and resource-assisted communication. Censorship protocols offer a novel perspective on quantum network security, that differs fundamentally from existing approaches such as quantum and postquantum cryptography.

We investigate the generation of entanglement between two noninteracting systems by synthesizing a quantum process from the superposition of distinct processes characterized by local-only operations. Our analysis leads to the derivation of a universal trade-off relation, $P_{\text{succ}}(1+\mathcal{C})\le 1$, that fundamentally bounds the success probability ($P_{\text{succ}}$) and the generated entanglement (concurrence $\mathcal{C}$). The derivation of this trade-off relation is inspired by indefinite causal order but applies to a broader class of quantum processes. Next, we show that the mathematical structure of this bound predicts the existence of a “quasideterministic” mode of operation, a surprising phenomenon which we then confirm with concrete entanglement generation protocols, where a maximally entangled state is guaranteed to be produced. In this mode of operation, both outcomes of the postselection measurement on the auxiliary control system result in a maximally entangled state of the target system. Furthermore, we demonstrate how this general principle can be realized using a quantum switch, which leverages an indefinite causal order as a physical resource, and explore the rich variety of dynamical behaviors governed by the universal trade-off. Our results establish a general principle for entanglement generation with superposition of quantum processes and introduce a way of controlling entanglement generation.

We derive a systematic technique that achieves optimal robust quantum control that is simultaneously robust against both detuning and pulse inhomogeneities by inverse optimization. The method, referred to as bi-RIO, is applied to produce birobust population transfer and notable quantum gates that are optimal with respect to the energy of the pulses, a major cost issue for quantum technologies. We show that, for a given performance in terms of fidelity and robustness, the bi-RIO pulses are much less energetic and faster than the composite pulses.

Although quantum resources such as entanglement and coherence have been utilized to enhance energy transfer from a quantum charger (QC) to a quantum battery (QB), squeezing remains a powerful yet underutilized resource in the charging process that warrants further exploration. Using pseudomode theory, we analyze the influence of a non-Markovian squeezed reservoir on charging performance under three protocols: (1) direct reservoir-mediated charging, (2) a hybrid scheme combining direct QC-QB interaction with reservoir-mediated coupling, and (3) the reservoir acting only as a charging environment. For a single non-Markovian squeezed reservoir, increasing the squeezing strength enhances the average charging power across all three scenarios—in contrast to its distinct effects on stored energy and extractable work under protocols (1) and (2). Within protocol (2) we identify an optimal phase for the direct QC-QB interaction that maximizes QB performance. Under protocol (3), stronger squeezing strength simultaneously improves the energy storage, average charging power, and extractable work. When extending the analysis to multiple squeezed reservoirs, we find that increasing their number further amplifies the average charging power in every protocol. These results provide a theoretical foundation for achieving high-performance QB charging through the use of non-Markovian squeezed reservoirs.

Noise is a hindering factor for current-era quantum computers. In this study, we experimentally validate the theoretical relationships between amplitude noise of the control signal and qubit state fidelity. The experiment comprises a $10\times 10$ site optical tweezer array stochastically loaded with single rubidium-85 atoms. A global microwave field is used to manipulate the state of the hyperfine qubits. With precise control of the time-dependent amplitude of the microwave drive, we apply control signals featuring artificial noise. We systematically analyze the impact of various noise profiles on the fidelity distribution of the quantum states. The measured fidelities are compared against theoretical predictions made using the stochastic Schrödinger equation. Our results show a good agreement between the experimentally measured and theoretically predicted results. This validation is consequential, as the model provides critical information on noise identification and optimal control protocols in noisy intermediate-scale quantum (NISQ)-era quantum systems.

In this work, we develop pulse designs and embedding strategies to improve the analog quantum subroutines of hybrid column generation (CG) algorithms based on neutral-atoms quantum computers (NAQCs). These strategies are designed to improve the quality and diversity of the samples generated. We apply these to an important combinatorial optimization (CO) problem in logistics, namely the fleet assignment. Depending on the instance tested, our quantum protocol has a performance that is either comparable to or worse than the best classical method tested, both in terms of the number of iterations and final objective value. We identify the cause of these suboptimal solutions as a result of our quantum protocol often generating high-quality but degenerate samples. We address this limitation by introducing a greedy postprocessing technique, Make_Diff, which applies bitwise modifications to degenerate samples in order to return a nondegenerate set. With this modification, our quantum protocol becomes competitive with an exact solver for the subproblem, all the while being resilient to state preparation and measurements errors. We also compare our CG scheme with a Gurobi solver and find that it performs better on over 50% of our synthetic instances and that, despite Gurobi having a more extensive runtime. These improvements and benchmarks herald the potential of deploying hybrid CG schemes on NISQ devices for industrially relevant CO problems.

Many-body correlation plays a crucial role in the low-energy positron-molecule scattering dynamics. In the present work, we have integrated a recent model correlation potential, developed by Swann and Gribakin, with the single-center expansion method and verified its efficacy in reproducing the best of ab initio and experimental results, for both nonpolar and polar molecules. Starting with the already tested molecules—hydrogen, ethylene, and acetylene—with the model correlation potential, we extended our calculations to oxygen-containing molecules: oxygen, water, and formic acid. In order to provide a comparative study, we have also performed calculations employing the model correlation potential of Perdew and Zunger. Integral, differential, and momentum transfer cross sections are reported for the target molecules. Positron virtual or bound state formation is also predicted using both of the model correlation potentials. Overall, an improved agreement of our results with the literature for the recent model suggests the approach can be employed for larger systems, where the ab initio techniques are difficult to implement.

We report Dirac-Fock calculations of transition energies for kaonic neon. For the most intense line, the 7–6 transition, the calculated energy is 9450.28 eV, which includes a bound-state quantum electrodynamics (BSQED) contribution of 12.66 eV. This is in excellent agreement with the recent SIDDHARTHA-2 measurement at $\mathrm{DA}\mathrm{\Phi }\mathrm{NE}$ of $9450.23\pm 0.37(\mathrm{stat}.)\pm 1.50(\mathrm{syst}.)\mathrm{eV}$. With the quantum electrodynamics contribution far exceeding experimental uncertainty, these results establish kaonic atoms as sensitive platforms for precision tests of BSQED in intermediate-Z systems.

We propose a polarization-resolved high harmonic spectroscopy scheme, which overcomes the limitations of the previous schemes when adopted in the two-dimensional (2D) synthetic driving fields. By numerically simulated experiments, we demonstrate the reconstruction of 2D electron trajectories driven by orthogonal two-color (OTC) fields with comparable intensities. Our method makes full use of the dynamical symmetry of the OTC field. Two weak lasers with different frequencies and polarizations are employed to perturb the balance of the subcycle interferometer, respectively. The electron dynamics are imprinted on the ellipticity modulation of high harmonics. The measured birth time of the attosecond pulse corresponds well with that calculated by the Gabor transform, and the average deviation is less than 10 as. Our results demonstrate that the electron has a nonzero longitudinal velocity at the ionization time, supporting the nonadiabatic tunneling regime. In addition, the nonzero tunneling exits are also reconstructed. Our work highlights the importance of the polarization information of harmonic spectra in reconstructions, especially for 2D problems.

We investigate a system composed of strings uniformly populated by dipolar Bose-Einstein condensates of magnetic atoms. Evaluating the interaction between a dipole belonging to a given string and all other dipoles in the system, we derive a two-dimensional discrete model featuring a specific form of the nonlocal nonlinear interaction, governed by the respective variety of the discrete Gross-Pitaevskii equation. By means of numerical methods, we construct four distinct types of strongly localized discrete solitons, labeled as in-phase single-peak (ISP), twisted single-peak (TSP), in-phase double-peak (IDP), and twisted double-peak (TDP) ones, which are determined by the orientation of the magnetic moments with respect to the underlying lattice. If the moments are polarized along the lattice diagonal, the discrete solitons exhibit a stable species with a different spatial profile from the above-mentioned modes. The characteristics and stability of the soliton families are systematically investigated. Calculation of the energy for these solitons demonstrates that the IDP type tends to be the system's ground state.

The radiative linewidth of a two-level emitter (TLE) fundamentally limits the bandwidth available for quantum information processing. Despite its importance, no prior experiment has systematically examined how driving detuning affects the indistinguishability of photons scattered from a TLE—a parameter critical for photonic quantum computing. Here, we perform postselective two-photon interference measurements between mutually detuned resonance-fluorescence signals from an InAs quantum dot embedded in a micropillar cavity. At small mutual laser detunings ($\le 0.5\mathrm{GHz}$), the results are accurately described by the pure-state model [Wang et al., Nat. Commun. 16, 6453 (2025)], which treats all resonance-fluorescence photons as spontaneous emission with no well-defined emission time prior to detection. At larger detunings, we uncover an anomalous feature in the two-photon interference, where the normalized second-order correlation function under orthogonal polarizations yields $g_{\perp }^{\left(2\right)}\left(0\right)<0.5$.

We demonstrate an experimental realization of cascaded resonance fluorescence over a 64-meter delay between two spatially and temporally independent ensembles of laser-cooled cesium atoms coupled to an optical nanofiber. Spontaneously emitted photons from a strongly driven first ensemble are guided through a standard fiber, reflected by a fiber Bragg grating mirror, and interact with a second ensemble, producing a unidirectional two-node cascaded system. The cascaded fluorescence spectrum is broadened and blueshifted relative to the original fluorescence spectrum. Our simple model reproduces the power broadening and the cascaded fluorescence spectrum, as well as the ratio of cascaded to original photon flux, giving insight into non-Markovian dynamics. Our results establish a long-distance one-way cascaded atom-photon interface, providing a stepping stone toward a fiber-based platform for quantum networking.

Entropic uncertainty relations have been a famed research topic for over 65 years with many applications and still many unknowns left. For example, even for single-qubit states, the optimal min-entropy uncertainty relation has only been found for pure states. In this paper we provide the optimal min-entropy uncertainty relation for mixed states of any purity for pairs of arbitrary qudit bases, marking a significant milestone in this journey. Moreover, our proof of optimality is constructive: for every base overlap and state purity we find an explicit example that saturates our bound.