This work investigates the impact of time rescaling on the performance of Feedback-Based Quantum Algorithms (FQAs) and their variant for optimization tasks, Feedback-Based Algorithm for Quantum Optimization (FALQON). We introduce the Time-Rescaled Feedback-Based Quantum Algorithm (TR-FQA) and Time-Rescaled Feedback-Based Algorithm for Quantum Optimization (TR-FALQON), time-rescaled versions of FQA and FALQON, respectively. The method is applied to two representative problems: the MaxCut combinatorial optimization problem and ground-state preparation in the axial next-nearest neighbor Ising (ANNNI) model. The results show that TR-FALQON accelerates convergence toward the optimal solution in the circuit's early layers and outperforms the standard version in low-depth regimes. In the context of state preparation, TR-FQA requires fewer layers than the original algorithm. These findings suggest that time rescaling can reduce the number of layers needed to reach a high-quality solution, even if the exact ground state is not obtained.

We demonstrate background-free imaging and sideband cooling of a single ${}^{133}\mathrm{Cs}$ atom via the narrow-line $6S_{1/2}\to 5D_{5/2}$ electric quadrupole transition in a 1064 nm optical tweezer. The $5D_{5/2}$ state decays through the $6P_{3/2}$ state to the ground state, emitting an 852 nm wavelength photon that allows for background-free imaging. By encoding both spin and orbital angular momentum onto the 685 nm excitation light, we achieve background-free fluorescence histograms with 99.58(3)% imaging fidelity by positioning the atom at the dark center of a vortex beam. Tuning the tweezer polarization ellipticity realizes a magic trap for the stretched $|F=4,m_F=4\rangle \to |F^{\prime }=6,m_F^{\prime }=6\rangle$ cycling transition. Using a Gaussian beam, we cool to $5\mu \mathrm{K}$ in a 1.1 mK trap and outline a strategy for ground-state cooling. We compare cooling performance across different sideband regimes, while also exploring how the orbital angular momentum of structured light controls the selection rules for quadrupole transitions. These results expand the toolbox for high-fidelity quantum control and cooling in alkali-atom tweezer arrays.

We present a strong-coupling expansion of the Bose-Hubbard model based on a mean-field treatment of the hopping term, while onsite fluctuations are taken into account exactly. This random phase approximation describes the universal features of the generic Mott-insulator–superfluid transition (induced by a density change) and the superfluid state near the phase transition. The critical quasiparticles at the quantum critical point have a quadratic dispersion with an effective mass $m^{*}$ and their mutual interaction is described by an effective $s$-wave scattering length $a^{*}$. The singular part of the pressure takes the same form as in a dilute Bose gas, provided we replace the boson mass $m$ and the scattering length in vacuum $a$ by $m^{*}$ and $a^{*}$, and the density $n$ by the excess density $|n-n_{\mathrm{MI}}|$ of particles (or holes) with respect to the Mott insulator. We define a universal two-body contact $C_{\mathrm{univ}}$ that controls the high-momentum tail $\sim 1/{\left|\mathbf{k}\right|}^4$ of the singular part $n_{\mathbf{k}}^{\mathrm{sing}}$ of the momentum distribution. We also apply the strong-coupling RPA to a lattice model of hard-core bosons and find that the high-momentum distribution is controlled by a universal contact, in complete agreement with the Bose-Hubbard model. Finally, we discuss a continuum model of bosons in an optical lattice and define two additional two-body contacts: a short-distance universal contact $C_{\mathrm{univ}}^{\mathrm{sd}}$ which controls the high-momentum tail of $n_{\mathbf{k}}^{\mathrm{sing}}$ at scales larger than the inverse lattice spacing, and a full contact $C$, which controls the high-momentum tail of the full-momentum distribution $n_{\mathbf{k}}$.

Dissipative-soliton resonance (DSR) is theoretically predicted to enable unlimited energy scaling while maintaining a constant power in dissipative systems. It has traditionally been regarded as a fully coherent structure. Here, through comprehensive simulations, we show that DSRs can exhibit partial coherence, characterized by stochastic temporal and spectral dynamics. Under appropriate saturation power of a nonmonotonic saturable absorber, the pulse develops a strong nonlinear chirp induced by self-phase modulation, which, in conjunction with normal dispersion, gives rise to wave-breaking-induced temporal fringes and the chaotic proliferation and decay of dark solitons. Concurrently, spatiotemporal intermittency emerges across the pulse plateau in the form of irregular patterns. These dynamics lead to stochastic temporal evolution and the degradation of spectral coherence, quantified by the decay of first-order spectral coherence between successive pulses. Nevertheless, the partially coherent DSR still exhibits characteristics similar to those of the coherent DSR, such as constant power and a pulse duration that increases with pump strength. Our results provide new physical insight into the coherence properties of DSRs and offer practical criteria for experimentally identifying the widely observed flat-top square pulses.

Light-matter strong coupling has been the subject of much attention in recent decades, giving optical systems unique features. However, properties of a system with strong coupling are determined by the properties of its components and are thus difficult to control. Here, we propose Floquet engineering, a technique of controlling the energy levels of a quantum system using external fields, as a method of manipulating a hybrid system of a molecule strongly coupled to a single-mode resonator. We show that an external field can change the relative positions of levels in an open strongly coupled system, leading to a change in the rates of transitions between them. We demonstrate that if the frequency of the pumping wave is close to polariton transitions in the hybrid system, nonmonotonic dependence of fluorescence and scattering amplitudes on pump intensity with a narrow resonance-like response occurs. We show that this phenomenon occurs due to hybridization of the lower and upper polaritons with substantially different excitation numbers caused by the pumping affecting polariton states of the system. This occurs when the Rabi interaction with the coherent field is comparable to the field-matter coupling constant, which in turn needs to be sufficient for the manifestation of strong coupling. This nonmonotonic dependence of the fluorescence and scattering amplitudes on pump rate intensity paves the way for the creation of nonlinear optical devices.

In standard treatments of open quantum systems, the reduced dynamics is described starting from the assumption that the system and the environment are initially uncorrelated. This assumption, however, is not always guaranteed in realistic scenarios and several theoretical approaches to characterize initially correlated dynamics have been introduced. For the uncorrelated scenario, stochastic unravelings are a powerful tool to simulate the dynamics. So far they have not been used in the most general case in which correlations are initially present since they cannot be applied to nonpositive operators or noncompletely positive maps. In our work, we employ the bath positive $(\mathrm{B}+)$ or one-sided positive decomposition (OPD) formalism as a starting point to generalize stochastic unraveling in the presence of initial correlations. Noticeably, our approach does not depend on the particular unraveling technique, but holds for both piecewise deterministic and diffusive unravelings. This generalization allows not only for more powerful simulations for the reduced dynamics, but also for a deeper theoretical understanding of open system dynamics.

Nonstabilizerness is an essential resource for quantum computational advantage as stabilizer states admit efficient classical simulation. We develop a semi-device-independent framework for certifying nonstabilizer states in prepare-and-measure (PAM) scenarios, relying only on assumptions about the system's dimension. Within this framework, we introduce PAM witnesses that can distinguish stabilizer from nonstabilizer states, and we provide analytical proofs that threshold violations of these witnesses certify nonstabilizerness. In the simplest setting—three preparations, two measurements, and qubit systems—surpassing a specific threshold guarantees that at least one prepared state lies outside the stabilizer polytope, while a stronger violation can certify at least two. We extend this approach by linking it to quantum random access codes, also generalizing our results to qutrit systems and introducing a necessary condition for certifying nonstabilizerness based on state overlaps (Gram matrices). These results offer a set of semi-device-independent tools for practically and systematically verifying nonstabilizer states using PAM inequalities.

Photoisomerization, a photochemical process underlying many biological mechanisms, has been modeled recently within the quantum resource theory of thermodynamics. This approach has emerged as a promising tool for studying fundamental limitations to nanoscale processes independently of the microscopic details governing their dynamics. On the other hand, correlations between physical systems have been shown to play a crucial role in quantum thermodynamics by lowering the work cost of certain operations. Here we explore quantitatively how correlations between multiple photoswitches can enhance the efficiency of photoisomerization beyond that attainable for single molecules. Furthermore, our analysis provides insights into the interplay between quantum and classical correlations in these transformations.

The Dicke-Ising model, one of the few paradigmatic models of matter-light interaction, exhibits a superradiant quantum phase transition above a critical coupling strength. However, in natural optical systems, its experimental validation is hindered by a “no-go theorem.” Here, we propose a digital-analog quantum simulator for this model based on an ensemble of interacting qubits coupled to a single-mode photonic resonator. We analyze the system's free-energy landscape using field-theoretical methods and develop a digital-analog quantum algorithm that disentangles qubit and photon degrees of freedom through a parity-measurement protocol. This disentangling enables the emulation of a photonic Schrödinger cat state, which is a hallmark of the superradiant ground state in finite-size systems and can be unambiguously probed through the Wigner tomography of the resonator's field.

We describe a quantum algorithm to simulate the time-dependent Hamiltonian, extending the methodology of quantum signal processing. The framework achieves optimal scaling up to some factor with respect to other parameters, and is nearly optimal in inverse of error tolerance, which could be improved to optimal scaling under certain input models. As applications, we discuss the problem of simulating tje generalized lattice system and time-periodic, or Floquet system, showing that our framework provides a neater yet highly efficient solution, achieving nearly optimal scaling in all parameters. In particular, our method also paves a new way for studying phase transition on quantum computer, extending the reach of quantum simulation.

The Cramér-Rao bound captures completely the performance of single-parameter quantum sensors. On the other hand, its extension to multiple parameters demands more caution. Different aspects need to be captured at once, including, critically, compatibility. In this article we consider compatibility in quantum interferometry for an important class of probe states, measured by double homodyne or photon counters, standard benchmarks for these applications. We include the presence of loss and phase diffusion in the estimation of a phase. Our results illustrate how different weighting of the precision on individual parameters affects their compatibility, adding to the list of considerations for quantum multiparameter estimation.

Topological Floquet energy pumps, which use periodic driving to create a topologically protected quantized energy current, have been proposed and studied theoretically, but have never been observed directly. Previous work [D. M. Long et al., Phys. Rev. Lett. 128, 183602 (2022)] proposed that such a pump could be realized with a strongly driven superconducting qubit coupled to a cavity. Here, we experimentally demonstrate that the proposed hierarchy of energy scales and drive frequencies can be realized using a transmon qubit. We develop an experimental toolkit to realize the adiabatic driving field required for energy pumping using coordinated frequency modulation of the transmon and amplitude modulation of an applied resonant microwave drive. With this toolkit, we measure adiabatic evolution of the qubit under the applied field for times comparable to $T_1$, which far exceed the bare qubit dephasing time. This result paves the way for direct experimental observation of topological energy pumping.

We propose a scheme for achieving quantum entanglement between surface-plasmon-polariton (SPP) modes in a hybrid plasmonic-graphene waveguide system. We then demonstrate that the entanglement of two SPP modes can serve as a useful resource for quantum communication of continuous-variable light signals over a long distance, mediated by concatenated swap operations. The teleportation fidelity of an unknown coherent state has strong robustness to loss and imperfect detection at relatively strong effective optical-microwave coupling. Our study opens the way for continuous-variable quantum communication and quantum information based on hybrid plasmonic-graphene systems.

We report methodological improvements to the Schwinger multichannel method in the static plus polarization (SP) approximation for low-energy positron-molecule scattering. The enhancements include the use of $f$-type Gaussian functions in the basis sets for both the positron and target molecules, as well as a refined placement of chargeless extra centers to better describe short-range positron-electron interactions. Annihilation parameters $Z_{\text{eff}}$ are calculated both directly and with enhancement factors to assess the role of correlation effects beyond the SP approximation. The improved approach is applied to positron scattering from hydrogen molecule, nitrogen molecule, methane, acetylene, and ethylene, resulting in cross sections and bound-state energies showing improved agreement with recent experimental and theoretical data.

We investigate theoretically high-order harmonic generation (HHG) and its ellipticity in gapped graphene, driven by a femtosecond short-pulse laser at various orientation angles, employing the two-band density-matrix equations within the tight-binding approximation. The orientation-dependent harmonic spectra exhibit pronounced enhancement of specific harmonics, which we attribute to the caustic effect. Using the recombination trajectory model, we reveal that the orientation dependence of these enhanced harmonics originates from the distinct band structures encountered by electrons ionized from the two inequivalent $\text{K}$ points. Moreover, we focus on the ellipticity of the enhanced harmonics at specific angles and demonstrate that it primarily depends on the phase difference between the parallel and perpendicular components, which can be accurately predicted by our recombination trajectory model. Based on these insights, we propose a two-color (fundamental plus second-harmonic) field scheme to generate isolated elliptically polarized attosecond pulses (IEAPs) in gapped graphene and discuss the dependence of IEAPs on the laser parameters and gap energy. Our findings may provide a promising pathway for generating IEAPs in gapped graphene or transition-metal dichalcogenides.

We present simulations of attosecond photoelectron momentum distributions for the ${\mathrm{H}}_2^{+}$ molecule by numerically solving the two-dimensional time-dependent Schrödinger equation (TDSE). We employ a semiclassical two-center interference model that incorporates the influence of the Coulomb potential on photoelectron phase modulation to interpret the calculated photoelectron angular distributions derived from TDSE simulations. Building on this model, we propose a methodology to reconstruct the molecular Coulomb potential using attosecond photoelectron momentum spectroscopy. The retrieved potential exhibits good consistency with the original input potential, thereby enabling direct imaging of the transient Coulomb potential during attosecond photoionization processes.

In this work, we propose an experimentally feasible nonlinear optical platform to realize nonintegrable geometric phases that emerge in interacting quantum systems undergoing quantum phase transitions. Specifically, we demonstrate that an exotic nonlinear term in the dynamical equations governs the polarization evolution of the optical field propagating along an anisotropic low-birefringence fiber with tetragonal symmetry. Intriguingly, by adiabatically tuning the nonlinear susceptibilities along the fiber, the Stokes vector on the Poincaré sphere accumulates a nonintegrable phase known as the Hannay angle—the classical counterpart to the Berry phase—which exhibits the same geometric gauge structure, including conic singularities in parameter space, as those associated with quantum phase transitions in systems like Bose-Einstein condensates. We further discuss a practical experimental implementation through the adiabatic deposition of nanocrystals along the fiber to control these susceptibilities, highlighting assumptions such as negligible losses and low birefringence for realistic fiber lengths.

Advances in lasers and atomic clock technologies have enabled delicate measurements to be made of minute relativistic effects. Here, we propose that such developments should lead to the measurement of relativistic effects involving atoms and molecules in dynamic optical traps. Specifically, we make a case for the study of time dilation in the context of atoms and molecules trapped in a rotating optical Ferris wheel. With experimentally relevant examples, we demonstrate how this would extend relativity tests down to the micron scale and would constitute a potential advance toward micron-size Mössbauer-style spectroscopy for trapped atoms and molecules.

Spin-orbit interactions (SOIs) of light are manifestations of coupling between components of light's angular momentum. They are at play in most basic optical processes, offering opportunities both to understand their fundamental origin and to control light in novel ways. Because SOIs become significant at subwavelength scale, they have largely been explored in the context of inhomogeneous materials exhibiting wavelength-scale structures and notably metamaterials. Here we demonstrate that spin-orbit interactions can in fact analogously emerge in moving matter through the well-known light-dragging effects. SOIs in moving media are shown to manifest through a Berry phase induced by vorticity, which then leads to a rotation of the wave's polarization. In bringing together electrodynamics of moving media and SOIs of light, our work not only paves the way for the discovery of fundamental effects but also uncovers alternative means to harness SOIs to control light.