We show that incoherent operations (IOs) can achieve the state transformations that are forbidden under dephasing-covariant incoherent operations (DIOs), thereby resolving the open problem posed by Chitambar and Gour [E. Chitambar and G. Gour, Phys. Rev. Lett. 117, 030401 (2016)]. We further demonstrate that no set of IO monotones suffices to characterize state convertibility under strictly incoherent operations (SIOs) and that monotones common to IOs and DIOs are insufficient to characterize convertibility under DIOs.

Identification of nonorthogonal quantum states without error is crucial for various applications in quantum information technology, as well as the foundations of quantum physics. Theoretical studies have proposed measurements that maximize the success probability of unambiguously discriminating quantum states. However, these methods are not always experimentally feasible, which has led most demonstrations to focus on equiprobable symmetric states. Here, we establish a projective measurement scheme that optimally discriminates multiple asymmetric qudit states. We experimentally demonstrate this optimal projective measurement using a photonic orbital angular momentum state, where asymmetric qudit states are encoded in the Laguerre-Gaussian modes of a heralded single-photon state. Our results have broad applications in high-dimensional quantum-state-based quantum information processing, including quantum key distribution and quantum sensing.

Spin-orbit coupling plays an important role in both fundamental physics and technological applications. Precise estimation of the spin-orbit coupling is necessary for accurate designing across various physical setups, such as solid-state devices and quantum hardware. Here, we exploit quantum features in a one-dimensional quantum wire for estimating the Rashba spin-orbit coupling with enhanced sensitivity beyond the capability of classical probes. The Heisenberg limited enhanced precision is achieved across a wide range of parameters and does not require fine tuning. Such an advantage is directly related to the gap-closing nature of the probe across the entire relevant range of parameters. This provides a clear advantage over conventional criticality-based quantum sensors in which quantum-enhanced sensitivity can only be achieved through fine tuning around the phase-transition point. We have demonstrated quantum-enhanced sensitivity for both single-particle and interacting many-body probes. In addition to extending our results to thermal states and the multiparameter scenario, we have provided a measurement basis to perform close to the ultimate precision.

High-sensitivity magnetometers play a crucial role in various domains, including fundamental physics, biomedical imaging, and navigation. Levitated diamonds containing nitrogen-vacancy centers exhibit significant potential for magnetic sensing due to their high mechanical quality factor and long spin coherence time. However, previous studies have predominantly focused on electron-spin-based measurements of alternating current magnetic fields. In this paper, we propose an approach for direct current magnetic-field measurement based on the Berry phase generated by three-dimensional rotation. We analyze the adiabatic evolution of the ${}^{14}\mathrm{N}$ nuclear spin inside a levitated three-dimensional rotating diamond with frequencies around $\mathrm{MHz}$. Our finding reveals that the Berry phase exhibits high sensitivity to external parameters near rotation-induced nuclear spin resonance. Using this mechanism, we theoretically demonstrate that a static magnetic-field sensitivity of ${10}^{-7}\mathrm{T}/\sqrt{\mathrm{Hz}}/\sqrt{N}$ is achievable as experimental techniques continue to mature.

High-sensitivity accelerometers and gravimeters, achieving the ultimate limits of measurement sensitivity, are key tools for advancing both fundamental and applied physics. While numerous platforms have been proposed to achieve this goal, from atom interferometers to optomechanical systems, all of these studies neglect the effects of intrinsic quantum uncertainty in time estimation. Starting from the Hamiltonian of a generic linear quantum sensor, we derive the two-parameter quantum Fisher information matrix and establish the corresponding Cramér-Rao bound, treating time as an uncertain (nuisance) parameter. Our analysis reveals a fundamental coupling between time and signal estimation that inherently degrades measurement sensitivity, with the standard single-parameter quantum limit recovered only at specific interrogation times or under special decoupling conditions. We then apply these results to an optomechanical gravimeter and explicitly derive an optimal decoupling condition under which the effects of time uncertainty are averaged out in a continuous measurement scheme. Our approach is general and can be readily extended to a broad class of quantum sensors.

Distributed quantum computing represents at present one of the most promising approaches to scaling quantum processors. Current implementations typically partition circuits into multiple cores, each composed of several qubits, with intercore connectivity playing a central role in ensuring scalability. Identifying the optimal configuration—defined as the arrangement that maximizes circuit Haar randomness generation with minimal depth—thus constitutes a fundamental design challenge. In this work, we demonstrate, both analytically and numerically, the existence of a universal optimal configuration for distributing single- and two-qubit gates across arbitrary intercore communication topologies in variational distributed circuits. Our proof is based on a Haar randomness measure based on Markov matrices, which quantifies the convergence rate towards the Haar measure [Y. S. Weinstein, W. G. Brown, and L. Viola, Phys. Rev. A 78, 052332 (2008)]. Finally, we validate our predictions through numerical comparisons with the well-established majorization criterion [J. Montes, F. Borondo, and G. G. Carlo, APL Quantum 2, 026104 (2025)].

We present relativistic many-body perturbation theory plus configuration interaction calculations of the lowest four excited states of ${\mathrm{Ni}}^{12+}$, a promising candidate for highly charged ion optical clocks. By combining the convergence behavior from multiple calculation models, we perform a detailed analysis of the electron-correlation effects and both the excitation energies and their uncertainties are obtained. Our computed energies for the first two excited states deviate from experimental values by less than $10{\mathrm{cm}}^{-1}$, with relative uncertainties estimated below $0.2\%$. Building on the same computational procedure, we calculate the mass shift and field shift constants for the lowest four excited states of ${\mathrm{Ni}}^{12+}$, and the resulting isotope shifts exhibit valence-correlation-induced relative uncertainties below the $1\%$ level. These results provide essential atomic-structure input for high-precision isotope shift spectroscopy in ${\mathrm{Ni}}^{12+}$.

In a combined experimental and theoretical study, Müller et al. [Phys. Rev. A 111, 053108 (2025)] revealed highly detailed resonant structure in ionization with excitation and in double ionization of the Li-like ${\mathrm{B}}^{2+}$ ion. That work demonstrated the strong predictive power of the convergent-close-coupling (CCC) method when enhanced by modern supercomputing technology. In the present work, we apply CCC to analogous ionization processes in the Li atom. Again, we find $K$-shell ionization accompanied by $K$-shell excitation to contribute relatively strongly to the double photoionization of three-electron Li. Comprehensive detailed comparisons with the existing experimental data are presented and discussed.

We present a multilevel pulse-area theorem for generating infrared pulses in combination with two time-delayed terahertz pulses, offering an advanced method for manipulating molecular quantum states. This approach enables precise control over molecules, starting from the ground state and driving them into a well-defined superposition of three rotational states within an excited vibrational level. To validate our theoretical model, we perform detailed time-dependent quantum wave-packet simulations of lithium hydride (LiH) molecules in their ground electronic state, accounting for both vibrational and rotational degrees of freedom. By jointly determining the optimal values of multiple pulse parameters (amplitudes, phases, and delays), we demonstrate highly accurate control over rotational superpositions at the chosen vibrational level and achieve the desired molecular orientation. Furthermore, we extend the theorem to encompass rotational excitations spanning two different vibrational subspaces and design optimized terahertz pulses tailored to control molecular orientations in excited vibrational states. We also investigate the influence of these customized terahertz pulses on rotational excitations within the ground vibrational level. This work establishes a theoretical framework for the precise and flexible control of both vibrational and rotational quantum states in molecular systems, with potential applications in quantum technologies and molecular spectroscopy.

We consider coherent states of weakly interacting bosons under the conditions of external resonant excitation, with a focus on a two-dimensional polariton fluid driven by a plane electromagnetic wave near the ground state. The coherent driving breaks the U(1) symmetry explicitly, which prevents the occurrence of quantum vortices in a uniform scalar condensate. Surprisingly, a spinor (two-component) system of the same kind admits topological excitations, such as domain walls of relative phase or confined half-vortex molecules, typical of a freely evolving spinor Bose system. Opposite-phase domains arise from the spontaneous breakdown of the spin symmetry $\left({\mathbb{Z}}_2\right)$. Domain walls form with time even when the initial state of the system is uniform or completely disordered; they fall into different topological types distinguished by the total phase variation in the transverse direction. One type of domain walls is similar to “magnetic” solitons in Bose-Einstein condensates and exhibits nonzero spin polarization whose sign depends on the direction of motion. Domain walls of the second type, by contrast, behave like monopoles with broken spatiotemporal symmetry and tend to move in certain preferred directions. The interaction of vortices and domain walls results in a long-range ordering of the system.

We present a detailed investigation of itinerant magnetism in a dipolar Bose gas of chromium atoms confined in a three-dimensional optical lattice, expanding on results recently reported in [Phys. Rev. Lett. 136, 103401 (2026)]. In the low-entropy, near-unit filling regime, we employ advanced dynamical decoupling techniques to suppress magnetic-field noise and probe spin coherence across the superfluid–Mott insulator transition. Here, we provide a systematic comparison of different dynamical decoupling sequences, analyze their robustness to experimental imperfections, and quantify their impact on spin dynamics. We also develop perturbative and effective-model approaches that capture the role of both contact and dipolar interactions in determining spin coherence. In the superfluid regime, we discuss a hydrodynamic description that elucidates the emergence and breakdown of metastable ferromagnetism. In the insulating regime, we derive effective spin models including superexchange terms. In this limit, we introduce a tractable spin-1 toy model and a short-time expansion of the full spin-3 dynamics that help to shed insight on the interplay between dipolar and contact-driven superexchange dynamics observed experimentally for spin-3. Our comprehensive analysis bridges experiment and theory, providing new tools and perspectives for understanding itinerant dipolar magnetism in optical lattices.

The realization of Bose-Einstein condensation under grand canonical conditions has provided the experimental evidence for the simultaneous occurrence of macroscopic fluctuations and phase coherence of the condensate. The observation of these two features, against a consolidated tradition which wants the fluctuations to be pathological (grand canonical catastrophe) and incompatible with spontaneous symmetry breaking, calls for a comprehensive rethinking of the approach to the problem. In this paper we consider the uniform ideal gas in a box and we present an alternative conceptual framework. We show that the usually employed Bogoliubov quasiaverage construction fails to reproduce the broken-symmetry state. The observed features are accounted for by a different pattern of spontaneous symmetry breaking, characterized by the condensation of fluctuations and long-range correlations of the order parameter.

We present a reduced-order semianalytical model for reorientational nonlinearity in chiral nematic liquid crystals, showing that the chiral pitch acts as the dominant physical length scale governing the onset of nonlinear self-focusing and soliton formation. Starting from the full Frank-Oseen equation, we derive a closed-form expression for the optically induced molecular rotation that captures the essential saturable response of the medium while reducing computational cost by more than two orders of magnitude compared with standard relaxation-method solvers. Despite its simplicity, the model reproduces the essential features of the numerically obtained nonlinear refractive index, the onset of self-localization, and the transition from discrete to continuous solitons in one and two dimensions. It further predicts the formation of fully localized astigmatic nematicons with only minor shifts in the self-localization threshold due to the neglect of nonlocal effects. The proposed model provides direct physical insight into light-matter interactions with soft matter media and offers a computationally efficient tool for the design and optimization of nonlinear photonic devices.

We adapt an algorithm for cnot circuits synthesis based on the Bruhat decomposition to the design of linear optical circuits with Mach-Zehnder interferometers. The synthesis algorithm reduces to designing sorting networks with nearest neighbor swapping operations as elementary gates. We recover previous designs from the literature with the additional property that the compiler can always decide whether a unitary can be implemented on a given interferometer and, if so, returns the shallowest possible implementation. We also show natural extensions of our framework for boson sampling experiments and for the coupling of multiple integrated interferometers to design larger linear optical systems. In both cases, the designs are optimal in terms of the number of optical components. Finally, we propose a greedy design which exploits the arbitrary-but-fixed coupling of separate integrated interferometers to perform shallow boson sampling. We discuss the optimal interferometer dimensions to maximize the transmission. Beyond boson sampling, our developed framework allows a resource-favorable implementation of any nonadaptive linear optical quantum algorithm, by providing the shallowest possible interferometer for implementing this algorithm.

Featuring unique properties, dissipative Kerr solitons generated in integrated ring microresonators (soliton microcombs) have a great potential for a wide range of practical applications. The direct resonance scanning method, assuming the increasing wavelength of the pump laser across a microresonator mode, is the most common and robust way for soliton state excitation. However, in this case the generation of soliton states is a probabilistic process, which hampers the development of microcomb-based devices for specific applications. In this paper, we investigated experimentally the probability of different soliton state excitations depending on the pump power, frequency scanning speed, and microresonator dispersion characteristics. Having conducted a statistical analysis of soliton states occurring for various microresonators, it was demonstrated that strong anomalous group velocity dispersion facilitates single-soliton state generation. Also, it was revealed that there is a cutoff value of the normalized pump amplitude, above which no soliton states can be excited. Our findings uncover some alternative patterns in the soliton excitation process through the direct resonance scanning method and, on the other hand, confirm some previously made numerical predictions. The obtained results can be utilized as a practical guide for designing microresonator-based devices to capable of generating a particular soliton state.

The preparation of quantum-dot qubits in the excited state is an integral part of the performance of an on-demand single-photon source (SPS). Conventional resonant excitation, an excellent approach to maximize the second-order coherence and indistinguishability of the SPS, often requires polarization filtering to remove the pump signal and isolate the qubit emission, but this results in an inherent 50% hit to the efficiency. Recent excitation schemes strategically try to exploit pulses that excite the qubit while avoiding spectral overlap to bypass this required filtering. In this work, we compare three such pumping schemes to quantify the important SPS figures of merit for off-resonant quantum-dot schemes using (1) a symmetrically detuned dichromatic pulse, (2) a notch-filtered adiabatic-rapid-passage (NARP) pulse, and (3) a swing-up of the quantum emitter population (SUPER) pulse. Due to large instantaneous pulse strengths, the dichromatic pulse suffers from phonon-induced dephasing which can lower the SPS performance by up to 50%. In contrast, the NARP and SUPER pulses are shielded from phonon coupling to differing degrees, but both maintain excellent SPS performance. The SUPER pulse can lose significant efficiency if there is variance in its constituent pulses' amplitude, pulse width, or frequency, while the NARP pulse, although potentially more difficult to realize in experiments, is robust against variance in the pulse preparation.

We study the coherent transport of one or two photons in a one-dimensional waveguide chirally coupled to a dissipative nonlinear cavity. The scattering amplitudes are derived analytically. With the assist of dissipation, we can realize an ideal single-photon diode whose transmittance is unity from one side and zero from the other side. A two-photon diode can be realized not only due to the two-photon bound state, but also the plane-wave part without photon correlation because of dissipation. The working area and properties of the two-photon diode are also found. This work details the relation between the diode effect and our system parameters, especially dissipation, which may find applications in nonreciprocal quantum devices and quantum networks.

We report a quantitative evaluation of weak-value amplification (WVA) for longitudinal phase measurements using Allan variance analysis. Building on a recent double-slit interferometry experiment with real weak values [Phys. Rev. Lett. 134, 080802 (2025)], our Allan variance analysis demonstrates measurement of a few attosecond time delay approaching the shot-noise limit at short averaging intervals of $T=0.01–0.1\mathrm{s}$, representing two orders of magnitude variance reduction compared to the $T=300\mathrm{s}$ operating point in prior implementations. We demonstrate that the Allan-variance noise floor scales with the inverse of the detected photon number $1/N_r$, confirming shot-noise-limited operation with WVA. Furthermore, this $1/N_r$ scaling experimentally validates that WVA can outperform conventional measurement under fixed detected photon number and detector saturation, in the presence of technical noise, as theoretically predicted [Phys. Rev. Lett. 118, 070802 (2017)]. Our results provide rigorous, quantitative evidence of the near-optimal noise performance achievable with WVA, establishing a benchmark for precision optical metrology. This advancement is particularly relevant to applications such as gravitational-wave detection, where signals predominantly occupy the high-frequency regime ($>10\mathrm{Hz}$).

The heralded optical parametric amplifier (OPA) has emerged as a promising tool for quantum state engineering. However, its potential has so far been limited to coherent state inputs. Here we introduce a generalized heralded OPA protocol that unlocks a vastly expanded class of quantum phenomena by accepting arbitrary nonclassical inputs. With a squeezed vacuum input, the setup functions as an integrated two-photon subtractor, nondeterministically generating high-fidelity, larger-amplitude squeezed Schrödinger cat (SC) states, an operation previously requiring complex, discrete setups. Furthermore, when fed a small-amplitude SC state, the protocol acts as a non-Gaussianity amplifier, distilling it into high-purity approximations of key quantum resources like specific photon-number superpositions. This work transforms the OPA from a specialized source into a versatile platform for advanced quantum state engineering. The integrated setup enables the generation of a wide array of non-Gaussian states, providing a unified approach to quantum state synthesis.