We present a quantum computation approach in which computation is guided by positive-operator-valued-measure (POVM) measurements following a given computation path in multisteps. In this approach, one ancillary qubit is coupled to a register of working qubits, and a POVM measurement is implemented effectively on the working qubits by applying a unitary operation on the whole system followed by a projective measurement performed on the ancillary qubit. Each step of the computation is a repeat-until-success procedure such that the desired state of the step is obtained deterministically on the working qubits via POVM measurements. The principle of deferred measurement states that measurements can always be moved from an intermediate stage of a quantum circuit to the end of the circuit without affecting the efficiency of the computation. We demonstrate that in our approach, by introducing intermediate measurements on the ancillary qubit in the computation process, both the number of qubits and unitary operations can be reduced polynomially, compared to the case where the intermediate measurements are deferred to the end of the computation. We also provide a method for implementation of the approach.

We initiate an investigation into a notion of state complexity for discrete-variable quantum systems. Specifically, we propose an information-theoretic quantifier for the complexity of quantum states within the stabilizer formalism of quantum computation. This is achieved by leveraging the symmetric Jordan product (associated with classicality) and the skew-symmetric Lie product (linked to quantumness) between the square root of the quantum state and the Heisenberg-Weyl displacement operators. We reveal fundamental properties of this quantifier and demonstrate that state complexity is closely related to the nonstabilizerness of quantum states via the $L^4$-norm of their characteristic functions. By the way, we characterize the maximally mixed states, the stabilizer states, and the symmetric informationally complete positive operator valued measure fiducial states from the perspective of state complexity.

We propose the first continuous-variable (CV) unclonable encryption scheme, extending the paradigm of quantum encryption of classical messages to CV systems. In our construction, a classical message is first encrypted classically and then encoded using an error-correcting code. Each bit of the codeword is mapped to a CV mode by creating a coherent state which is squeezed in the $q$ or $p$ quadrature direction, with a small displacement that encodes the bit. The squeezing directions are part of the encryption key. We prove unclonability in the framework introduced by Broadbent and Lord, via a reduction of the cloning game to a CV monogamy-of-entanglement game. Furthermore, we demonstrate that our scheme can be readily implemented with current technology. By incorporating realistic imperfections such as channel noise and detector inefficiencies, we show that the protocol remains robust under these conditions.

A protocol for identifying controlled-not (cnot) gates versus single-qubit-only gates in universal quantum circuits using randomized input states was recently shown to be intimately connected to the quantum resource of state texture. Here, we revisit this gate identification protocol and demonstrate that a more general fidelity-based formulation succeeds for nearly all laboratory bases. We then examine a broader family of quantum resource theories, where a distinct resource theory can be defined for each choice of reference pure state, establishing core resource-theoretic requirements without the computational shortcut offered by the “grand sum” employed in the original formulation of state texture. By extending from single “resourceless” states to convex sets via a convex-roof construction, we recover single-qubit measures of known resource theories such as imaginarity and coherence. Finally, we introduce a family of “fixed-point resource theories” that includes fixed-point instances of the theories of state texture, genuine coherence, purity, and athermality. For these fixed-point resource theories we show that under free operations the fidelity-based lower bound is weakly monotonic, while specific violations of strong monotonicity are found for the convex-roof logarithmic measure.

Dissociative electron attachment to N-ethylacetamide is investigated using velocity map imaging with a tunable electron beam. Previously reported ion-yield spectra reveal two prominent resonant features near 5.5 and 8.8 eV across all observed anion channels. Surprisingly, no distinct structure is observed in the intermediate 6–7-eV energy region, where smaller amides typically exhibit an additional resonance associated with amide-bond cleavage. For N-ethylacetamide, the absence of a clear feature in this energy region indicates that any corresponding transient negative-ion state does not contribute significantly to dissociation. The momentum distributions obtained in the present work reveal distinct dissociation dynamics for different channels. The ${\mathrm{CH}}_3{}^{-}$ fragment at 5.5 eV exhibits an anisotropic distribution, indicating a direct dissociation process with finite kinetic-energy release. In contrast, the ${\mathrm{NH}}^{-}$ fragment at 8.8 eV shows an isotropic distribution with near-zero kinetic energy, which suggests a three-body dissociation process. These results demonstrate that the observed resonances correspond to qualitatively different dissociation mechanisms and suggest that the intermediate resonance, if present, does not drive efficient or direct fragmentation in N-ethylacetamide.

Relativistic effects have a profound impact on the electronic structure of the heaviest elements, and consequently on their chemical and physical properties. In order to investigate these effects, we developed an ion mobility spectrometer equipped with a cryogenic drift tube to measure the reduced mobilities of the ions of monoatomic lanthanides and actinides. As a benchmark, we conducted the first systematic study of lutetium cations (${\mathrm{Lu}}^{+}$) drifting in helium at 298 K, resolving ground and metastable electronic states using electronic state chromatography. We compared the state-specific mobilities with predictions based on state-of-the-art ab initio calculations, and they show very good agreement. Our work paves the way for atomic structure studies in the region of the superheavy elements and provides a powerful experimental approach for exploring ion-neutral interactions and electronic configuration effects in heavy element systems.

We present a purely theoretical, fully analytical momentum-space description of “superkick” momentum transfer to a two-level atom driven by a tightly focused, circularly polarized Laguerre-Gaussian vortex beam. Using the short-time excitation amplitude ${\psi }_e(\mathbf{r},t)\propto E_z\left(\mathbf{r}\right){\psi }_g\left(\mathbf{r}\right)$ and an exact Fourier-transform treatment in the near-focus regime, we derive closed-form expressions for the excited-state wave function ${\tilde{\psi }}_e\left(\mathbf{K}\right)$ and its momentum distribution $|{\tilde{\psi }}_e{\left(\mathbf{K}\right)|}^2$. This framework yields direct superkick diagnostics such as peak displacement and transverse-momentum moments, and enables a systematic comparison between opposite-handedness and same-handedness configurations, as well as a paraxial reference case. We show that tight focusing, through the longitudinal-field enhancement, strongly increases the near-axis excitation and makes superkick signatures most prominent in the opposite-handedness configuration, whereas the same-handedness and paraxial reference cases retain related transverse superkick structure but carry much smaller near-axis probability weight.

We provide a fully analytical derivation of Anderson's orthogonality catastrophe for the one dimensional Fermi polaron integrable model, describing a system of $N$ spin-up fermions, with fixed density $n=N/L$, interacting with a single spin-down fermion via an attractive contact potential. The proof combines the determinant representations of the norm of the many-body wave function and of its scalar product with the noninteracting ground state, obtained from the Bethe-ansatz solution, with the special properties of Cauchy matrices. We derive the leading asymptotics of the two determinants in the thermodynamic limit and show that the quasiparticle residue $Z$ decays algebraically, $Z=W{N}^{-\theta }$. We confirm that the Anderson exponent $\theta$ is equal to $2{\delta }_F^2/{\pi }^2$, where ${\delta }_F$ is the Bethe-ansatz phase shift at the Fermi edge. We also derive the asymptotic behavior of the prefactor $W$ at strong coupling and compare it against exact numerics.

We study spin and density excitations of one-dimensional self-bound Bose-Bose droplets within Bogoliubov theory and show that spin excitations come alive, especially as the interspecies coupling is made less attractive. We argue that spin excitations are particularly relevant in the one-dimensional droplet regime, where droplets are realized within the mean-field stability regime, as has been confirmed by the quantum Monte Carlo simulations. As the interspecies coupling strength increases within the mean-field stability regime, spin modes ultimately fall below the particle-emission threshold, thus becoming observable in the droplet spectrum. We analyze the Bogoliubov model for both pseudospinor and population-imbalanced scalar mixtures, encompassing both the density and spin sectors. We corroborate our findings through variational analysis of density- and spin-breathing modes, which offers physical insight into the mode structure and independently validates the spectrum, as well as through real-time dynamics. Additionally, we compare our results with both Petrov's original theory, which considers the Lee-Huang-Yang (LHY) correction at the attractive edge of the mean-field stability regime, and a beyond-LHY description of Bose-Bose mixtures.

Nonequilibrium transport remains a central theme in modern physics, spanning from condensed matter to synthetic systems. Here, we investigate particle transport in an extended Aubry-André model with system-scale hopping, namely, nonlocal hopping with a range proportional to the system size, and uncover a metal-insulator coexistence regime in real space, where metallic and insulating spatial domains coexist within the same system and are separated by sharp spatial boundaries. In the insulating region, particles exhibit flat-band-like localization in the absence of quasiperiodic potentials, while a quasiperiodic potential induces distinct multipoint localization, different from conventional exponential localization. Meanwhile, particles can freely propagate and tunnel across spatially disconnected metallic domains separated by the insulating region. Beyond this coexistence phase, we identify unconventional gap-crossing domain-wall modes with comblike spatial profiles that mediate nonlocal, multipoint transport across separated metallic domains. Our findings reveal a rich interplay between localization, nonlocality, and transport in systems with nonlocal hopping.

We investigate the variability of the quantum coherences of an arbitrary density matrix, in a given basis. An easily computable quantity that captures this variability notion is proposed and a dual relationship with an appropriate entropy is observed, with coherence dispersion (CD) being maximized for intermediate values of disorder and vanishing for extremal entropy values. This is a prevalent signature of complexity quantifiers across different fields, from evolutionary biology to information science. In addition, the physical significance of CD is investigated in the context of entropy production in open systems. We also study a specific family of nonequilibrium systems for which coherence dispersion presents a peaked maximum for finite temperatures. The final part of the manuscript is dedicated to the application of CD as a key ingredient to establish quite general quantum speed limits in the Hilbert space.

We find that the seemingly disparate control approaches for classical and quantum continuous-variable systems can be unified via differential manifolds of the ancillary representations. For classical systems, the ancillary representation is defined by the time-dependent ancillary canonical variables resulting from symplectic transformation over the original canonical variables. Under the Hamilton-Jacobi theory, the ancillary canonical variables act as dynamical invariants to guide the system nonadiabatically through the entire phase space. The second quantization of the Liouville equation for the dynamical invariants leads to the Heisenberg equation for the relevant ancillary operators, which is found to be a sufficient condition to activate nonadiabatic passages toward arbitrary target states in both Hermitian and non-Hermitian systems and yield constrained exact solutions of the time-dependent Schrödinger equation. Using the non-Hermitian Hamiltonian rigorously derived from the Lindblad master equation, our theory is exemplified by the generation of single-mode squeezed states with a squeezing level about 29.3 dB and double-mode squeezed states with 20.6 dB, respectively.

We consider the problem of identifying the quantum spin states that are the optimal sensors of a given transformation, averaged over all possible orientations of the spin system. Our geometric approach to the problem is based on a fidelity criterion and is entirely general, encompassing any unitary transformation. This formalism leads to a universality result: For any value of the spin, there exists a zero-measure subset of states that can be the optimal sensors for certain transformations and the worst sensors for others, and this set does not depend on the transformation under consideration. In other words, some spin states are simply the best (or worst) sensors, regardless of what they detect.

We investigate the performance of the charger-mediated quantum battery modeled by a two-qubit system. One of the qubits acts as the battery and the other acts as the charger, which is subjected to a reservoir. We derive the time-local master equation in Lindblad form with a time-dependent dephasing rate. The dephasing rate may be negative in the early stage of the charging process and thus indicate the presence of the memory effect. We find that such early-stage memory effect could increase the maximal ergotropy of the battery compared with the one under Markovian approximation with the corresponding asymptotic dephasing rate. The enhancement of the performance is explained by means of the non-Markovian quantum jumps. Moreover, a discrete-time scheme of the measurement-enhanced quantum battery is proposed in a quantum circuit with global and random local operations.

Dynamic quantum circuits generate states that depend on the measurement results obtained during circuit execution. To date such a quantum computing model has mainly been implemented with qubit-based superconducting hardware utilizing reset operations and classical logic. Here we develop a model of optical reset by using time-bin self-looped interferometers demonstrated in recent experiments. Synchronizing the optical reset with a simple classical device storing history of measurement results allows one to decrease uncertainty of future measurements, which suggests new possibilities for constructing dynamical circuits on optical platforms. Information flow with significant multitime correlations and memory depth is identified through distinct information-theoretic measures. We discuss potential applications of the proposed reset model, including the realization of boson sampling and experimental tests of the quantum-mechanical formulation of Landauer's principle.

Simulating the dynamics of non-Hermitian quantum systems is essential for probing the frontiers of modern physics. However, existing quantum algorithms are fundamentally constrained by the probability loss inherent to probabilistic postselection, extensive quantum circuit depths, and the substantial overhead of ancillary qubits. Herein, we introduce a hybrid quantum-classical algorithm grounded in quantum circuit Monte Carlo (QCMC) to concurrently address both limitations. By reformulating nonunitary evolution as statistical sampling of Hamiltonian dynamics, our framework alleviates the probability loss issue induced by postselection, achieves a reduction in quantum circuit depth, and requires at most one additional ancillary qubit. This general and flexible approach is capable of simulating arbitrary, time-dependent, and even nondiagonalizable Hamiltonians, providing a unified solution for diverse problems including parity-time ($\mathcal{PT}$)-symmetric systems, open quantum systems usually governed by completely positive trace-preserving (CPTP) maps, as well as non-CPTP maps. We demonstrate our method on a many-body open system, achieving excellent agreement with exact solutions. This work provides a resource-efficient pathway for exploring different phenomena in complex non-Hermitian systems on near-term quantum devices.

We present the simultaneous trapping and cooling of ${}^{85}\mathrm{Rb}$, ${}^{87}\mathrm{Rb}$, and ${}^{133}\mathrm{Cs}$ in a triple-species magneto-optical trap (MOT). This demonstration is obtained using an all-fiber compact and robust laser system based on telecom 1.5- and 2-$\mu \mathrm{m}$ technologies. We characterize the two-body interspecies losses in the double- and triple-species MOT. We calculate the two-body interspecies trap-loss coefficient for the ${}^{85}\mathrm{Rb}\text{−}{}^{133}\mathrm{Cs}$ and the ${}^{87}\mathrm{Rb}\text{−}{}^{133}\mathrm{Cs}$ pairs, representing a variation of less than 7% in atom number. No losses are observed between ${}^{85}\mathrm{Rb}$ and ${}^{87}\mathrm{Rb}$ in our experimental conditions. We find that interspecies interactions inside the triple-species MOT do not prevent trapping and cooling ${10}^8$ atoms for each species, making our system suitable for future multispecies cold-atom interferometry applications.

The nonadiabatic wavepacket dynamics is used to calculate the excitation and quenching cross sections in the ${\mathrm{N}}^{+}\left({}^3\mathrm{P}\right)–\mathrm{He}\left({}^1\mathrm{S}\right)$ and ${\mathrm{N}}^{+}({}^1\mathrm{D}$)–He(${}^1\mathrm{S}$) collisions using potential energy curves and spin-orbit coupling elements calculated ab initio. The results are verified by comparison with cross sections calculated by solving the time-independent coupled Schrödinger equation with the logarithmic derivative method, as well as with cross sections calculated semiclassically using the Landau-Zener method. The comparison shows that the wavepacket dynamics can be used for both the excitation and the quenching processes at energies ranging from 0.01 to 0.02 Hartree above the activation energy up to the energies of the order of 10 Hartree.

Programable photonic meshes provide a promising platform for analog matrix-vector multiplication, but their scalability is often limited by the large phase-shift ranges required in universal interferometer circuits. We introduce a perturbative programing method that operates the circuit near a fixed reference configuration and realizes the target transformation through interferometric subtraction, thereby reducing the required programable phase excursion. We develop this approach for photonic matrix-vector multiplication architectures based on universal unitary meshes and for low-depth nonunitary constructions based on sums of unitaries. We identify favorable reference configurations through a local conditioning criterion, analyze the phase statistics obtained for random target matrices, and show that perturbative programing produces phase distribution shrinking as the matrix size increases. Identified reference point allows for the subtraction to be carried out electronically after detection, avoiding the interferometric subtraction loss. We further quantify the trade-off between the reduced phase range and the intrinsic overhead introduced by the subtraction architecture and show that for sufficiently lossy phase shifters the reduced phase range can compensate for this penalty. These results identify perturbative programing as a conditional but potentially useful route toward more scalable programable photonic matrix processors.

Integrated single-photon filters capable of spectral purification and mode selection are essential components for scalable quantum photonics. However, achieving on-chip filters with sharp roll-offs and high reconfigurablity remains challenging in quantum photonics, due to the requirement of a large number of accurately coupled high-Q stages. We propose a Bragg grating chain of quantum emitters as an on-chip spectral filter with a near-rectangular response, enabling efficient suppression of sideband emission from solid-state single-photon sources without loss of brightness. The proposed architecture allows continuous tuning of both the central frequency and bandwidth. Crucially, spectral filtering of a weak coherent-state pulse by the atomic chain significantly reduces the two-photon component, demonstrating strong nonlinearity at the single-photon level. This nonlinear filter offers a promising route to simultaneously enhance the indistinguishability and purity of quantum resources.