The thin-film planar cavity implanted in the $\mathrm{M}\ddot{\mathrm{o}}\mathrm{ssbauer}$ nuclei has been developed as a powerful platform to study the light-matter interaction in the x-ray band. Herein the asymmetric and symmetric profiles of Fano interference are studied by controlling the collective effect and modifying the cavity structure. It is found that the asymmetric profiles in the overcritical and undercritical regimes are the Fano-Lorentz shape, and the asymmetry of the profile is determined by $\cos \phi$ rather than $\cot \phi$ in the framework of the initial Fano theory with $\phi$ being the phase shift of the continuum. In addition, the Fano-Lorentz profile not only can be controlled by the phase difference of the two pathways, but also can be adjusted by the weight of the normal Fano resonance in the Fano-Lorentz profile through regulating the collective effect of the nuclear ensemble. By varying the nuclear abundance at the cavity mode angle, the transformation between the symmetric peak and valley is observed in the overcritical regime, whereas the symmetric peaks are always presented in the undercritical regime. Furthermore, a particularly interesting phenomenon of a flat reflectivity, as if the resonant nuclear ensemble is not excited, is predicted in the nuclear ensemble at a critical nuclear abundance in the overcritical regime. The present results will not only confirm the presence of the complex $q$, but also open up an avenue to study the decoherence processes via the Fano-Lorentz shape in the thin-film planar cavity.

An ultrasensitive optical whispering-gallery mode (WGM) sensor is highly desirable for detecting nanoparticles and has been widely used in human disease diagnosis and environment monitoring. The sensing mechanisms of a WGM sensor include mode shift, mode splitting, and mode broadening. To enhance mode broadening is a quite useful way to improve the sensitivity for detecting lossy nanoparticles, but it has not been realized. Here, we propose a feasible scheme for realizing a single-lossy-nanoparticle sensor with a dissipatively coupled photonic molecule and show that the significant enhancement of mode broadening can be obtainable at exceptional points when compared with a single-microcavity sensor subject to the same perturbation. The enhancement of mode broadening originates from the complex-square-root topology near exceptional points and the unique feature of level attraction in dissipative coupling, i.e., the repelled damping parameters of supermodes. Furthermore, we show that the enhancement factor in mode broadening is larger than that in mode splitting when the dissipatively coupled photonic molecule works in the strong-coupling regime. Therefore, our scheme may be useful to resolve smaller changes in mode broadening and improve the detection limit of lossy-nanoparticle sensing.

Coherent long-range interactions between atoms are a prerequisite for numerous applications in the field of quantum information science. Here we present an appealing method to dramatically enhance the long-range atom-atom interaction mediated by a coupled-cavity array that is subjected to two-photon (parametric) drives. Our method allows one to greatly amplify both the localization length of the single-photon bound-state wave function and the effective atom-photon coupling strength, resulting in a significant improvement of photon-mediated coherent interaction between two distant atoms. Additionally, we illustrate this effect by analyzing how it facilitates the transfer of information and the creation of entanglement between the atoms.

Entropy production and the detailed fluctuation theorem are of fundamental importance for thermodynamic processes. In this paper we study the multiple entropy production for multitime quantum processes in a unified framework. For closed quantum systems and Markovian open quantum systems, the given entropy productions all satisfy the detailed fluctuation relation. This also shows that the entropy production rate under these processes is non-negative. For non-Markovian open quantum systems, the memory effect can lead to a negative-entropy production rate. Thus, in general, the entropy production of the marginal distribution does not satisfy the detailed fluctuation theorem relation. Our framework can be applied to a wide range of physical systems and dynamics. It provides a systematic tool for studying entropy production and its rate under arbitrary quantum processes.

We analyze a quantum wire that consists of a linear chain of three qutrits with nearest-neighbor interactions and detuning on the central qutrit. We derive the detuning conditions for perfect state transfer of a double excitation and for maximal entanglement between the first and third qutrits. We also analytically determine the times for perfect state transfer and maximal entanglement, which are found to be periodic. We also show that perfect state transfer is a necessary condition for maximal entanglement, with the first occurrence of maximal entanglement at half the time for the first occurrence of perfect state transfer.

We examine the electron-positron pair-creation process from the quantum vacuum triggered by two colliding laser beams in the presence of a nuclear binding potential. Once the two pulses overlap, they form a standing-wave pattern with nodes or antinodes in the region where the nucleus is placed. As the resulting spatial intensity pattern depends on the phase between both fields, it can be used to control the pair-creation yield. It turns out that the ground-state capture of the created electrons can actually be largest for those laser phases that lead to nodes (dark intensity regions) where the nucleus is located and not for those that lead to antinodes (bright intensity regions). Furthermore, this phase can be used to control selectively into which excited state the created electrons are predominately captured.

Bose mixture quantum droplets display a fascinating stability that relies on quantum fluctuations to prevent collapse driven by mean-field effects. Most droplet research focuses on untrapped or weakly trapped scenarios, where the droplets exhibit a liquidlike flat density profile. When weakly trapped droplets rotate, they usually respond through center-of-mass motion or splitting instability. Here, we study rapidly rotating droplets in the strong external confinement limit where the external potential prevents splitting and the center-of-mass excitation. We find that quantum droplets form a triangular vortex lattice as in single-component repulsive Bose-Einstein condensates (BECs), but the overall density follows the analytical Thomas-Fermi profile obtained from a cubic equation. We observe three significant differences between rapidly rotating droplets and repulsive BECs. First, the vortex core size changes markedly at finite density, visible in numerically obtained density profiles. We analytically estimate the vortex core sizes from the droplets' coherence length and find good agreement with the numerical results. Second, the change in the density profile gives a slight but observable distortion to the lattice, which agrees with the distortion expected due to nonuniform superfluid density. Lastly, unlike a repulsive BEC, which expands substantially as the rotation frequency approaches the trapping frequency, rapidly rotating droplets show only a fractional change in their size. We argue that this last point can be used to create clouds with lower filling factors, which may facilitate reaching the elusive strongly correlated regime.

A recent experiment [R. C. Shen et al., Phys. Rev. Lett. 129, 123601 (2022)] has demonstrated the occurrence of nonlinearity-induced asymptotic bistability in cavity magnomechanics. As an extension, we explore the theoretical ground of diverse potential self-sustaining effects in cavity magnomechanics by analyzing its nonlinear dynamics. The attractors which suggest dynamical multistability for the limit cycles are mapped out to the parameter space by deriving the corresponding slow amplitude dynamics. Our quantitative analysis also includes the fluctuation-dissipation process, which quantitatively predicts non-Gaussian phase spreading, amplitude squeezing, and the mixture of multiple limit cycle states. We finally explore the quantum self-sustaining dynamics by solving the full quantum master equation. The paper lays the foundation for various applications, e.g., high-precision measurements, squeezed-state and non-Gaussian-state preparation, and nonlinearly induced quantum phase transitions, based on cavity magnomechanics.

The optical rectification effect is observed in periodically structured metal films (metasurfaces) with broken inversion symmetry. It is found that the finite width of the metasurface and the proximity of its edges also provide a symmetry-breaking mechanism, adding to the rectification current, which is further enhanced at surface plasmon polariton resonances. By position- and angle-resolved measurements we show that this mechanism is more efficient than the symmetry breaking achieved either by the oblique incidence of the laser light or by a nonsymmetric structure of the unit cell. The existing theory of the optical rectification can partially account for the observed phenomena.

Quantum nonlocality, a form of nonclassicality, serves as a crucial resource in quantum information processing. Nonlocality in quantum systems is exemplified by the perfect discrimination of orthogonal quantum states through single joint measurements, which is unattainable using local operations and classical communication (LOCC). Bandyopadhyay [S. Bandyopadhyay, Phys. Rev. Lett. 106, 210402 (2011)] established that, with LOCC alone, at most $N-1$ copies of $N$ orthogonal quantum states are required for perfect discrimination. Here, we present the experimental verification of orthogonal quantum state discrimination employing LOCC. Our results demonstrate that up to three copies suffice for the perfect distinction of four orthogonal two-qubit states via LOCC. The verified method of perfectly distinguishing orthogonal quantum state sets offers potential applications in quantum information processes, including quantum secret sharing and quantum teleportation.

We investigate the limits on cooling and work extraction via Markovian thermal processes assisted by a finite-dimensional memory. Here the memory is a $d$-dimensional quantum system with trivial Hamiltonian and initially in a maximally mixed state. For cooling a qubit system, we consider two paradigms: cooling under coherent control and cooling under incoherent control. For both paradigms, we derive the optimal ground-state populations under the set of general thermal processes (TP) and the set of Markovian thermal processes (MTP), and we further propose memory-assisted protocols, which bridge the gap between the performances of TP and MTP. For the task of work extraction, we prove that when the target system is a qubit in the excited state the minimum extraction error achieved by TP can be approximated by Markovian thermal processes assisted by a large enough memory. Our results can bridge the performances of TP and MTP in thermodynamic tasks including cooling and work extraction.

A multicenter continuum distorted wave with eikonal initial state model for single ionization of molecules by energetic ion impact is developed. The multicenter nature of the molecular ion is explicitly taken into account, within the framework of the independent electron approach, where the interaction between the ejected electron and the residual molecular ion is described by an anisotropic model potential. The method is employed to calculate doubly and singly differential cross sections of the water molecule by energetic ${\mathrm{H}}^{+}$, ${\mathrm{C}}^{6+}$, and ${\mathrm{O}}^{8+}$ projectiles. The discussion of the results is primarily focused on the emission of low-energy electrons, where the evaluated cross sections are compared with experimental and available theoretical data.

Ionization is one of the most fundamental processes in intense laser-matter interaction. It is extremely efficient for clusters in laser fields and often leads to surprisingly high charge states at moderate laser intensities. Here we show an interesting ionization mechanism in laser-cluster interaction through particle-in-cell simulations. As the laser field ionizes a cluster, Brunel electrons pushed back into the clustered plasma form attosecond bunches, impulsively exciting plasma oscillation. The resulting localized wake field further ionizes the cluster, causing a highly ionized rodlike core along the polarization axis. This anisotropic ionization is prominent using few-cycle pulses and may be washed out using longer pulses due to collisional ionization. This unexpected ionization channel can potentially provide complicated site-specific control of high ionization in nanometer-scale targets.

We formulate a quantum theory of photon emission during strong-laser-field-induced ionization and show that such photons can be emitted in a single-step process. The probability of this process is many orders of magnitude higher than that of the well-known high-order harmonic generation, which is a three-step process. We analyzed photon emission for various wavelengths and intensities of the laser field and found that the probability of photon emission is maximal for energies near 5 eV and that it can be shifted to higher energies for higher intensity. For a bichromatic linearly polarized laser field the photon emission rate can be controlled with the relative phase between the field components and can be one order of magnitude higher than in the monochromatic case. For circular laser polarization the rate of photon emission is lower than for the linear one and it depends on the emitted photon direction (it is much lower if the emitted photon polarization is perpendicular to the laser-field polarization plane). For the counterrotating bicircular field the rate is much higher than for the corotating bicircular field, monochromatic circularly and linearly polarized fields, and bichromatic linearly polarized field. The rate is the highest for orthogonally polarized two-color field for the relative phase $\pi /2$.

The resonant dynamic Stark effect, observed in the Autler-Townes (AT) splitting, plays a central role in ultrafast strong-field physics. Recent experiments have demonstrated the phase control of the AT doublet in atomic resonance-enhanced multiphoton ionization using intense resonant shaped femtosecond laser pulses [Bayer et al., Adv. Chem. Phys. 159, 235 (2016)]. Based on a two-state model, we showed that the underlying control mechanism is the selective population of dressed states (SPODS). In this work, we use a numerical model to calculate the photoelectron momentum distribution (PMD) based on the ab initio solution of the two-dimensional (2D) time-dependent Schrödinger equation (TDSE) to obtain a more complete physical picture of the nonperturbative control of the AT doublet. The 2D-TDSE model reproduces the ultrafast switching among the AT components while also revealing deviations from the signatures predicted by the two-state model. These deviations are attributed to the influence of additional intermediate states. To rationalize our observations, we propose a refined five-state model that includes all significantly populated bound states from the full calculation and accurately reproduces the 2D PMD. Based on the validated five-state model, we conduct a dressed-state analysis which provides a clear physical picture of the SPODS mechanism in a multistate system and sheds light on the role of the intermediate states in strong-field control.

Multifrequency Raman generation is a promising method of producing ultrashort laser pulses with high intensities and visible wavelength frequencies. Experimental realizations of multifrequency Raman generation have a spectrum that displays several behaviors that are not explained by theories calculating the relative Raman order amplitudes. We derive an analytic and perturbative expression for the spectra of the individual Raman orders radiated by a Raman medium excited by multiple Gaussian laser pulses. We use a method of Dawson function approximations to derive an analytic spectrum showing that the Raman order spectra are dependent on both the energy and chirp of the pumps, as observed experimentally.

We study the controllable output field generation from a cavity magnomechanical resonator system that consists of two coupled microwave resonators. The first cavity interacts with a ferrimagnetic yttrium iron garnet (YIG) sphere providing the magnon-photon coupling. Under a passive cavities configuration, the system displays high absorption, prohibiting output transmission even though the dispersive response is anomalous. We replace the second passive cavity with an active one to overcome high absorption, producing an effective gain in the system. We show that the deformation of the YIG sphere retains the anomalous dispersion. Further, tuning the exchange interaction strength between the two resonators leads to the system's effective gain and dispersive response. As a result, the advancement associated with the amplification of the probe pulse can be controlled in the proximity of the magnomechanical resonance. Furthermore, we find the existence of an upper bound for the intensity amplification and the advancement of the probe pulse that comes from the stability condition. These findings may find potential applications for controlling light propagation in cavity magnomechanics.

We investigate the resolution for imaging two pointlike entangled sources by using the method of moments and spatial-mode demultiplexing, where the pointlike entangled sources can be generated by injecting single-mode sources with arbitrary quantum statistics distribution into an optical parametric amplifier (OPA). We demonstrate that the separation estimation sensitivity is mainly determined by the photon distribution in each detected mode and it can be enhanced by either increasing the squeezed parameter of the OPA or eliminating the relative phase difference of the entangled sources. Furthermore, in the limiting case of infinitely small source separation, the usage of entangled sources can have better resolution than those using incoherent and coherent sources. The results here can find important applications for quantum super-resolution imaging and quantum metrology.