The Gottesman-Kitaev-Preskill (GKP) encoding is a top contender among bosonic codes for fault-tolerant quantum computation. However, analysis of the code is complicated by the fact that finite-energy code states leak out of the ideal GKP code space and are not orthogonal. We analyze a variant of the GKP stabilizer measurement circuit that virtually projects onto the ideal GKP code space between rounds of error correction, even when damped, finite-energy GKP states are used. This allows us to identify logical maps between projectors; however, due to finite-energy effects, these maps fail to resolve completely positive, trace-preserving (CPTP) channels on the logical GKP code space. We present two solutions to this problem based on channel twirling the damping operator. The first uses symmetries of standard binning (SB) decoding to passively twirl over the full stabilizer group. Doing so converts small amounts of damping into stochastic Gaussian random noise (GRN). The second uses active twirling over a minimal set of representative Pauli shifts that keeps the energy in the code finite and allows for arbitrary decoding. This approach is not limited to small damping and allows the study of decoding more general than SB, which can be optimized to the noise in the circuit. Focusing on damping, we compare decoding strategies tailored to different levels of effective squeezing. While our results indicate that SB decoding is suboptimal for finite-energy GKP states, we observe that the advantage of optimized decoding shrinks as the energy in the code increases. Moreover, the performance of both decoding strategies converges to that of the stabilizer-twirled GRN logical channel. These studies provide stronger arguments for two commonplace procedures in the analysis of GKP error correction in the fault-tolerance regime: $\left(i\right)$ using stochastically shifted GKP states in place of coherently damped ones, and $\left(ii\right)$ the use of SB decoding.

We present two deterministic compilation algorithms for single-qutrit unitaries with $O(log1/\varepsilon )$ gate depth. Each algorithm selects a nearby approximation to the target unitary and then exactly synthesizes the approximation over the Clifford $+$ $\mathbf{R}$ basis. The first algorithm exhaustively searches over the group; while the second algorithm searches only for Householder reflections. The exhaustive search algorithm yields an average $\mathbf{R}$ count of $2.193\left(11\right)+8.621\left(7\right){log}_{10}(1/\varepsilon )$, albeit with a time complexity of $O\left({\varepsilon }^{-4.4}\right)$. The Householder search algorithm results in a larger average $\mathbf{R}$ count of $3.20\left(13\right)+10.77\left(3\right){log}_{10}(1/\varepsilon )$ at a reduced time complexity of $O\left({\varepsilon }^{-0.42}\right)$, greatly extending the reach in $\varepsilon$. These costs correspond asymptotically to 35% and 69% more non-Clifford gates compared with synthesizing the same unitary with two qubits. Such initial results are encouraging for using the $\mathbf{R}$ gate as the nontransversal gate for qutrit-based computation.

The study of state revivals has long advanced our understanding of dynamical systems. We introduce a resource theory framework to study the use of state revivals in quantum information. In this theory, a state is said to contain no amount of resource if it experiences perfect revivals under some unitary evolution. All other states are said to be resourceful. The resource, which we dub “nonrevivals,” quantifies a state's inability to experience revivals. We use our framework to understand revivals in quantum many-body scarred systems and their applications. In particular, we show that quantum many-body scarred dynamics can produce revivals in the Hayden-Preskill decoding protocol and can also be used to recover damaged quantum information. We also use our resource theory to bound information scrambling. Our theory establishes a framework to study information retrieval and its applications in quantum many-body physics.

Programmable quantum systems based on Rydberg atom arrays have recently emerged as a promising test bed for combinatorial optimization. Indeed, the maximum weighted independent set problem on unit-disk graphs can be efficiently mapped to such systems due to their geometric constraints. However, extending this capability to arbitrary graph instances typically necessitates the use of reduction gadgets, which introduce additional experimental overhead and complexity. Here, we analyze the complexity‐theoretic limits of polynomial reductions from arbitrary graphs to unit‐disk instances. We prove any such reduction incurs a quadratic blow up in vertex count and degrades solution approximation guarantees. As a practical alternative, we propose a divide‐and‐conquer heuristic with only linear overhead, which leverages precalibrated atomic layouts. We benchmark it on Erdös-Rényi graphs, and demonstrate feasibility on the Orion Alpha processor.

We implement the Wormhole-Inspired Teleportation Protocol (WITP) in a pair of coupled Sachdev-Ye-Kitaev (SYK) models prepared in a thermofield-double state, forming a quantum analog of a traversable wormhole. By varying parameters (temperature $\beta$, coupling strength $g$, insertion site, and traversal time $t$) we compare the teleportation fidelity against an analogous protocol using a transverse-field Ising model. We find that the chaotic SYK system consistently yields higher teleportation fidelity than the transverse field Ising model, reflecting the SYK Hamiltonian's pronounced many-body chaos. These enhanced fidelities arise from the SYK's effectively random-matrix dynamics, which improve the coherent information transfer through the wormhole channel. Unlike prior single-qubit benchmarks based on $|0\rangle$ inputs, the present work defines and evaluates a genuine quantum-state fidelity for a maximally entangled two-qubit Bell input, using a Pauli-stabilizer formalism that captures entanglement-phase coherence. Our central result is achieved by teleporting a maximally entangled two-qubit Bell state through the wormhole. We introduce a Pauli-stabilizer fidelity measure for the two-qubit message and demonstrate that the Bell-state protocol produces a substantial fidelity boost compared to single-qubit teleportation. Furthermore, we examine the time-resolved fidelity for both single-qubit and two-qubit messages, revealing distinct fluctuation patterns that deepen our understanding of dynamical many-body teleportation processes. Finally, we present an argument that our Bell-state WITP simulations provide a concrete numerical testbed for aspects of the ER = EPR conjecture, by mapping entanglement structure and thermal/coupling dependence to traversability diagnostics in an emergent wormhole geometry.

Multipartite entanglement is regarded as a crucial physical resource in quantum network communication. However, due to the intrinsic complexity of quantum many-body systems, identifying a multipartite entanglement measure that is both efficiently computable and capable of accurately characterizing entanglement remains a challenging problem. To address these issues, we propose a family of two-parameter multipartite entanglement measures for mixed states, termed unified-entropy concentratable entanglements. Many well-known multipartite entanglement measures are recovered as special cases of this family of measures, such as the entanglement of formation and the concentratable entanglements introduced by Beckey et al. [Phys. Rev. Lett. 127, 140501 (2021)]. We demonstrate that the unified-entropy concentratable entanglements constitute well-defined entanglement monotones and establish several desirable properties they satisfy, such as subadditivity and continuity. We further investigate the ordering relations of unified-entropy concentratable entanglements and discuss how these quantities can be efficiently estimated on near-term quantum devices. As an application, we demonstrate that the unified-entropy concentratable entanglements can effectively distinguish between multiqubit Greenberger-Horne-Zeilinger states and W states. The ordering relations of these entanglement measures are further validated using four-partite star quantum network states and four-qubit Dicke states. Moreover, we find that the unified-entropy concentratable entanglements exhibit greater sensitivity than the original concentratable entanglements in detecting certain four-partite star quantum network states.

Surface codes are promising for practical quantum error correction due to their high threshold and experimental feasibility. However, their performance under realistic noise conditions, particularly those involving correlated errors, requires further investigation. In this study, we systematically investigate the effect of several distinct types of correlated errors that could potentially arise from next-nearest-neighbor coupling in quantum systems. Our analytical results reveal that these correlated errors exhibit lower logical error rates due to their inherent structural symmetries. We further perform circuit-level simulations that incorporate realistic circuit level errors alongside correlated noise components, demonstrating that surface code performance is intimately related to the structural characteristics of the correlation patterns. This deepens our insights into the threshold of surface code and hence facilitates a more robust design of quantum circuits with a higher noise threshold.

We introduce two variations of the quantum phase estimation algorithm: quantum shifted phase estimation and quantum punctured phase estimation. The shifted method employs a bit-string left shift to discard the most significant bit and focus on lower-order phase components, and the punctured method removes qubits corresponding to known phase bits, thereby streamlining the circuit. To demonstrate the effectiveness of the two variations, we integrate them into a hybrid quantum-classical implementation of the Harrow–Hassidim–Lloyd algorithm for solving linear systems. The hybrid method leverages both quantum and classical processors to identify and remove unnecessary qubits and gates. As a result, for small-scale linear systems, our method reduces qubit and gate counts relative to previous implementations, yielding lower overall circuit error rates on current hardware. Experimental demonstrations on IBM superconducting hardware confirm the error-mitigation effectiveness on small problem instances.

Hyperentanglement can enlarge the information capacity of quantum information processes, but its quality will be decreased by environment noise. Here, we present a single-copy-based hyperentanglement purification protocol (HEPP) to improve the quality of the polarization-spatial hyperentangled photon state suffering from amplitude-damping noise. By using the local high-dimensional positive-operator-valued measure, a high-quality hyperentangled photon state can be purified from one copy of a noisy hyperentangled state without being destroyed, where only linear optical elements are required. Compared with the previous multicopy-based HEPPs, this single-copy-based HEPP can rapidly increase the fidelity of the noisy hyperentangled state with considerable success probability using fewer entanglement resources and it can extend the scope of application to a wider fidelity range of noisy hyperentangled states. Hence this work will have extensive applications in quantum information technology.

The molecular convergent close-coupling (MCCC) method is utilized to calculate cross sections for electron scattering on the ground state of ${\mathrm{Li}}_2$. A model-potential approach is used to represent ${\mathrm{Li}}_2$ as a quasi-two-electron system above a frozen core, and configuration-interaction calculations are performed to obtain the valence states. Cross sections are calculated at incident electron energies between 0.01 and 500 eV, for elastic, excitation, ionization, and total scattering. Comparison is made with previous results where available. For the elastic-scattering cross section, qualitative agreement is found with previous calculations at low incident energies, and quantitative agreement is found at higher energies. The previously predicted ${}^2{\mathrm{\Pi }}_u$ shape resonance is also found in the present calculations, but at a substantially lower energy and with a larger magnitude. Mixed agreement is found with previous calculations for the excitation of the $1{}^1\mathrm{\Sigma }_u^{+}$ and $1{}^3\mathrm{\Sigma }_g^{+}$ states, and for ionization. The MCCC total cross section is in reasonable agreement with the only available experiment at incident energies greater than 0.5 eV.

Three-body Förster resonances controlled by a dc electric field are of interest for the implementation of three-qubit quantum gates with single atoms in optical traps using their laser excitation into strongly interacting Rydberg states. In our recent theoretical paper [Zh. Eksp. Teor. Fiz. 168, 14 (2025)], it was found that the proposed earlier three-body Förster resonance $3\times n{P}_{3/2}\to n{S}_{1/2}+(n+1)S_{1/2}+n{P}_{1/2}$ in Rb Rydberg atoms presents a splitting, with one of the split components having weaker dependence of the resonant electric field (and the corresponding dynamic shift) on the distance $R$ between the atoms. Here we study this effect in more detail, since this resonance appears as the most suitable for performing experiments on observing coherent oscillations of populations of collective three-body states and implementing three-qubit quantum gates based on them. For a linear spatial configuration of three interacting Rydberg atoms, the physical mechanism of this phenomenon is revealed and analytical formulas are obtained that describe the behavior of split structure of the Förster resonance depending on $R$. It is found that the splitting is a measure of the energy of the resonant dipole-dipole exchange interaction with an excitation hopping between neighboring Rydberg states $S$ and $P$.

We demonstrate a dual magneto-optical trap (MOT) of ${}^{109}\mathrm{Ag}$ and ${}^{39}\mathrm{K}$. For silver, a decreasing-field Zeeman slower loads a MOT of $1.5\times {10}^8$ atoms at a temperature of 0.74(5) mK, with laser cooling occurring primarily on the $D_2$ line of $4d^{10}5s{}^{2}S_{1/2}\to 5p{}^{2}P_{3/2}$ at 328 nm. We create a Ag “dark spot MOT,” where shelving the atoms in a dark state enhances the captured atom number by a factor of 2 and the lifetime by a factor of 4. For potassium, we obtain $2\times {10}^8$ trapped atoms, and further cooling on the $D_1$ transition via gray molasses results in a cloud of $1.2\times {10}^8$ atoms at $7\left(1\right)\mu \mathrm{K}$. We observe evidence of photoionization loss of the K MOT in the presence of Ag laser-cooling light, necessitating sequential rather than simultaneous loading for the two species. Our results on Ag point to simple and general laser cooling strategies for other coinage metals (Au, Cu). Furthermore, this work lays the foundation for the production of alkali-metal–coinage-metal degenerate quantum mixtures and highly polar molecules.

Vacuum fluctuations give rise to effective nonlinear interactions between electromagnetic fields. These generically modify the characteristics of light traversing a strong-field region. X-ray free-electron lasers (XFELs) constitute a particularly promising probe, due to their brilliance, the possibility of precise control and favorable frequency scaling. However, the nonlinear vacuum response is very small even when probing a tightly focused high-intensity laser field with XFEL radiation and direct measurement of light-by-light scattering of real photons and the associated fundamental physics constants of the quantum vacuum has not been possible to date. Achieving a sufficiently good signal-to-background separation is key to a successful quantum vacuum experiment. To master this challenge, a dark-field detection concept has recently been proposed. Here we present the results of a proof-of-principle experiment validating this approach by demonstrating that using real-world x-ray optics the background signal can be suppressed sufficiently to measure the weak nonlinear response of the vacuum.

In the context of orbital angular momentum (OAM) associated optical chirality, the involvement of photonic spin angular momentum and higher-order transition moments has long been regarded as essential. To date, the existence of helical dichroism that is exclusively determined by OAM remains elusive. Through the excitation of plasmonic surface lattice resonances (SLRs), we report a polarization-independent helical dichroism without the engagement of electric quadrupole moments, a scenario previously deemed implausible. Using a modified dipole sum under rotational symmetry, the theoretical framework of SLRs is successfully generalized to plasmonic helices. Our results reveal that the arbitrary plasmonic helix can be structurally optimized to exhibit both narrowband SLR peaks and polarization-independent helical dichroism. Notably, SLRs excitation can simultaneously generate tightly confined near-fields and collimated far-field radiation, which facilitate the OAM transfer in the chiral interaction and directional OAM projection, respectively. This work may clarify the intrinsic physics governing OAM-mediated chirality, potentially enabling advances in enantioselective detection and vortex-enhanced spectroscopy.

The geometric spin Hall effect of light (GSHEL), which is associated with nonzero transverse angular momentum, has been demonstrated to occur without a light-matter interaction and is characterized by a transverse shift. Recently, there has been a surge in research on spatiotemporal optical vortices (STOVs) that carry transverse angular momentum. In this study, we examine the transverse shift of a STOV in a tilted reference frame with respect to the propagation axis. Through both theoretical analysis and numerical simulations, we find only “spatial symmetrical STOVs” exhibit the GSHEL which can be divided into two types based on the direction of the vortices. Our findings reveal that this phenomenon is contingent upon the spatial distribution of their angular momentum density. In addition, we explore a maximum shift value, which is proportional to $\sqrt{l{x}_0/k_0}$ due to the uncertainty principle. These discoveries open up new avenues for applications in the realms of ultrafast optics and nanotechnology, offering a fresh perspective on the manipulation and measurement of light at the micro- and nanoscales.

Detecting Pancharatnam-Berry (PB) or geometric phases of light usually requires complex interferometry or diffraction through a specially designed truncated aperture. In this work, we present a simpler method that enables directly visualized measurement of geometric phases in certain complex structured light fields, without additional interferometry or beam truncation. Our approach exploits the PB phase present in SU(2) structured light. In these SU(2) modes, spatial wave packets naturally align with underlying caustic trajectories. By observing wave-packet evolution, i.e., the morphology of coupled caustics as the beam propagates, we can visually reveal both the geometric phase and the Gouy phase of the beam. This visual detection technique offers insights into the geometric phase of structured light and broadens the possibilities for designing optical devices that harness geometric phases.

While a thermodynamic description of light has been very useful in discussing light propagation in multimode nonlinear waveguides, it is often stated that such a description is not simple for free-space beams due to the onset of an ultraviolet catastrophe. Herein it is proposed that the beam width and divergence angle are natural cutoffs that remove the singular behavior. Also, the beam propagation (or quality) factor can be associated with a statistically defined temperaturelike parameter. In the high-temperature limit, the beam wavefront is described by a Gaussian Schell-model source, being strongly multimode with a specklelike intensity pattern. In the low-temperature limit the beam has a wandering Gaussian profile, showing strong correlations and anticorrelations for the intensity's Pearson correlation coefficient, with good agreement between numerical simulations and experimental data. Hence, the present results may subsidize the emerging discussions of thermodynamical descriptions in a wider range of optical systems, such as propagation in turbulent media or biological tissues. Moreover, this work's description is not limited to optical systems, since it is founded on a simple unbounded scalar linear system described using a complete orthonormal basis. Therefore, our findings may also provide further conceptual connections with properties of other systems, such as acoustic waves and quantum particles.

The far-field polarization of a photonic crystal (PhC) slab is inherently linked to its spatial symmetries. We demonstrate that introducing a parity-time ($\mathcal{PT}$)-symmetric perturbation—while breaking up-down mirror symmetry—leads to the emergence of a Janus bound state in the continuum (BIC) and a momentum-space ring of lasing threshold modes. Starting from a PhC slab that hosts both symmetry-protected BIC and accidental BICs, we investigate the effects of $\mathcal{PT}$-symmetric perturbations on these states. The perturbation transforms accidental BICs into pairs of circularly polarized states ($C$ points) and induces a ring of lasing threshold modes in momentum space, while leaving the symmetry-protected BIC unaffected. As the perturbation strength increases, four $C$ points on one side merge with the symmetry-protected BIC, whereas those on the opposite side remain separate, giving rise to a Janus BIC characterized by asymmetric topological charges in the upward and downward radiation. Meanwhile, the ring of lasing threshold modes expands, enhancing the quality ($Q$) factor of nearby resonant modes due to the diverging $Q$ at the lasing threshold. As a result, $C$ points with ultra-high-$Q$ factors emerge, offering new opportunities for advanced chiral light-matter interactions and vortex beam generation.

By solution of the inverse problem of classical electrodynamics, we propose a construction of nearly arbitrary spatially localized structured electromagnetic pulses, including wave packets with temporal polarization singularities. The latter are based on the topology of electric field hodographs. They encompass topological knots of both finite and infinite complexity and polarization ribbons, including one-sided Möbius stripes of variable width. These electromagnetic wave packets are generated by the localized dynamics of positive and negative electric charges and currents in a zero-net-charge plasma. The admissible electric field distributions are constrained by the requirement that the field of the pulse's electric area, the time integral of the electric field, must be curl-free. Our results open new avenues for the complete spatiotemporal structuring of ultrashort electromagnetic pulses; generalizations for a wide class of vector fields of various natures are possible.

A fundamental problem in quantum optics is to measure a quadrature operator of a mode described by a shape in the time or frequency domain. This can be done by pulsed homodyne detection, in which the signal and a high-amplitude pulsed local oscillator (LO) interfere on a beam splitter whose output ports are monitored by photodetectors. The quadrature value is proportional to the difference between the photodetectors' signals. When the shape of the mode is too broad in frequency, the lack of uniform spectral response of detectors prevents direct application of this technique. We show that pulsed homodyne detection can be generalized to broadband pulsed (BBP) homodyne detection with detectors such as calorimeters that detect total energy instead of total photon number. This generalization has applications in measurements of femtosecond pulses and, speculatively, of Rindler modes. We analyze how the implemented measurement approaches an ideal quadrature measurement with growing LO amplitude, and we prove that the moments of the measurement converge to the moments of the quadrature and that the measurement distributions converge weakly.