We experimentally study three-body Coulomb explosion of methane molecules, i.e., ${\mathrm{CH}}_4{}^{3+}\to {\mathrm{H}}^{+}+{\mathrm{H}}^{+}+{\mathrm{CH}}_2{}^{+}$ in 800-nm laser pulses with different intensities. We find that, at a relatively low intensity, the three-body breakup channel is dominated by a concerted pathway with a high kinetic energy release (KER). However, at a high laser intensity, an extra pathway with a low KER appears. The pathway with a low KER can be explained as a sequential pathway, indicating the potential existence of a stable intermediate ${\mathrm{CH}}_3{}^{2+}$ dication during the three-body Coulomb explosion of methane molecules in strong laser pulses. The intensity dependence of the pathway is explained as the increasing population on the excited state of ${\mathrm{CH}}_3{}^{2+}$ with the increase of the laser intensity, which has a longer lifetime than that of the ground state.

Different types of Young's double-slit experiments contain a significant amount of both particle and wave information running from full-particle to full-wave knowledge depending on the experimental conditions. We study the Young's double-slit interference in resonant Auger scattering from homonuclear diatomic molecules where opposite Doppler shifts for the dissociating atomic slits provide path information. Different quantitative formulation of Bohr's complementarity principle—path information vs interference—is applied to two types of resonant Auger scattering experiments, with fixed-in-space and randomly oriented molecules. Special attention is paid to the orientational dephasing in conventional Auger experiments with randomly oriented molecules. Our quantitative formulation of the complementarity is compared with the formulation made earlier by Greenberger and Yasin [D. M. Greenberger and A. Yasin, Phys. Lett. A 128, 391 (1988)].

An all-optical method for directly reconstructing the spectral phase of an isolated attosecond pulse (IAP) has been proposed recently [New J. Phys. 25, 083003 (2023)]. This method is based on high-harmonic-generation (HHG) streaking spectra generated by an IAP and a time-delayed intense infrared (IR) laser, which can be accurately simulated by an extended quantitative rescattering model. Here, we extend the retrieval algorithm in this method to successfully retrieve the spectral phase of a shaped IAP, which has a spectral minimum, a phase jump about $\pi$, and a “split” temporal profile. We then reconstruct the carrier-envelope phase of the IR laser from HHG streaking spectra. Finally, we discuss retrieval of the phase of high harmonics by the intense IR laser alone using the Fourier transform of HHG streaking spectra.

We developed a magneto-optical trap reaction microscope (MOTREMI) for strontium atoms by combining multiparticle coincident detection with the laser cooling technique. The present compact injection system enables the production of cold Sr atoms in three modes of two-dimensional (2D) magneto-optical trap (MOT) beam, molasses, and three-dimensional (3D) MOT, providing adjustable densities and ratios of the ground state $5s^2$ (${}^{1}S_0$) and the excited states $5s5p{}^1{P}_1$ and ${}^{3}P_J$. The target profiles including temperature, density, and size of the 3D MOT as well as the 2D MOT beam cold atomic flux were characterized in detail. Using the present setup, we investigate the single photoionization of Sr atoms with molasses through few-photons absorption in 800 nm, where ${\mathrm{Sr}}^{+}$ and $e^{-}$ are detected in coincidence and most of the ionization channels are identified. The momentum resolution for coincident ${\mathrm{Sr}}^{+}$ and $e^{-}$ along time-of-flight direction are achieved up to 0.12 a.u. and 0.02 a.u., respectively. The spectra of photoelectron ionized from the ground state as well as several excited states show distinct structures manifesting prominent contributions from multiphoton absorption. Detecting complete vector momenta of electrons and recoil ions in coincidence paves a way for further investigation of two-electron correlation dynamics and multielectron effects with alkaline-earth atoms.

We explicitly show that the differences, with respect to the appearance of topological phases, between the traditional Haldane model, which utilizes a honeycomb lattice structure, and the Haldane model imbued onto a brick-wall lattice geometry are inconsequential. A proposal is then put forward to realize the Haldane model by exploiting the internal degrees of freedom of atoms as a synthetic dimension. This leads to a convenient platform for the investigation of chiral edge states due to the hard boundaries provided by the hyperfine manifold. We make some cursory comments on the effects of interactions in the system.

We consider the ground states, excitations, and dynamics of a quasi-two-dimensional binary dipolar Bose-Einstein condensate. Our focus is on the transition to a spin-stripe ground state in which the translational invariance is spontaneously broken by a striped immiscible pattern of the alternating components. We develop a ground-state phase diagram showing the parameter regime where the spin-stripe state occurs. Using Bogoliubov theory, we calculate the excitation spectrum and structure factors. We identify a balanced regime where the system has a ${\mathbb{Z}}_2$ symmetry, and in the spin-stripe state this yields a nonsymmorphic symmetry. We consider the evolution of the system following a quench from the uniform to spin-stripe state, revealing ordering dynamics involving defects of the stripe order. Using an order parameter to characterize the orientational order of the stripes, we show that the phase ordering exhibits dynamic scaling.

We propose to achieve a multicolor nonreciprocal optical amplifier, a crucial device in optical communication and information processing, by spinning an active resonator. We show that in such a device, due to the interplay of the Sagnac effect and the optical gain, nonreciprocal signal amplification can be realized, accompanied by a giant enhancement of optical group delay from $0.3\mathrm{ms}$ to $35\mathrm{ms}$ in a chosen direction, which is otherwise unattainable in a passive device. Also, coherent amplification of higher-order optical sidebands and a slow-to-fast light switch can be achieved by tuning both the pump power and the spinning velocity. Our work provides a unique and accessible way, well compatible with other existing techniques, to realize multicolor nonreciprocal optical amplifiers for more flexible control of optical fields.

Feedback control can be used to generate well-determined nonlinear effective potentials in an optical trap, a goal whose applications may range from nonequilibrium thermodynamics to the generation of non-Gaussian states of mechanical motion. Here, we investigate the action of an effective feedback-generated quartic potential on a levitated nanoparticle within the perturbation regime. The effects of feedback delay are discussed and predictions from the perturbation theory of a Brownian particle subjected to a quartic anharmonicity are experimentally verified.

We demonstrate both theoretically and experimentally beam-dependent photonic spin-orbit coupling in a two-wave mixing process described by an equivalent of the Pauli equation in quantum mechanics. The considered structured light in the system is comprising a superposition of two orthogonal spin-orbit-coupled states defined as spin-up and -down equivalents. The spin-orbit coupling is manifested by prominent pseudospin precession as well as spin-transport-induced orbital angular momentum generation in a photonic crystal film of wavelength thickness. The coupling effect is significantly enhanced by using a deep-subwavelength carrier envelope, different from previous studies which depend on materials. The beam-dependent coupling effect can find intriguing applications; for instance, it is used in precisely measuring variation of light with spatial resolution up to 15 nm.

We explore the phenomenon of orbital angular momentum (OAM) transfer within a high-quality single-crystal diamond mechanical resonator containing nitrogen-vacancy (NV) centers. By employing a weak acoustic field in conjunction with two microwave fields, we establish a three-level closed-loop system within the spin-triplet ground states $3A$ of the NV center. Analytical findings illuminate the potential for OAM transfer to take place, originating from Laguerre-Gaussian microwave fields and extending to the input acoustic field, consequently engendering an acoustic vortex. In this context, the initial weak microwave probe field is presumed to possess OAM content, and the transference of OAM to the input acoustic field is meticulously examined through the mechanism of three-wave mixing under the condition of multiphoton resonance. We extend our investigation to encompass a composite acoustic vortex, accounting for nonzero radial indices and topological charges attributed to both microwave fields. The outcomes of this paper bear significance as they hold the promise of refining the precision of acoustic sensors deployed in applications encompassing sonar systems, nondestructive testing, medical procedures, medical imaging, and synchronized acoustical tweezers.

We analytically tackle optovibronic interactions in molecular systems driven by either classical or quantum light fields. In particular, we examine a simple model of molecules with two relevant electronic levels, characterized by potential landscapes with different positions of minima along the internuclear coordinates and of varying curvatures. Such systems exhibit an electron-vibron interaction, which can be composed of linear and quadratic terms in the vibrational displacement. By employing a combination of conditional displacement and squeezing operators, we present analytical expressions based on a quantum Langevin equations approach, to describe the emission and absorption spectra of such nonlinear molecular systems. Furthermore, we examine the imprint of the quadratic interactions onto the transmission properties of a cavity-molecule system within the collective strong-coupling regime of cavity quantum electrodynamics.

The Glauber-Sudarshan, Wigner and Husimi quasiprobability distributions are indispensable tools in quantum optics. However, although mathematical relations between them are well established, not much is known about their operational connection. In this paper, we prove that a single composition of finite-strength quantum limited amplifier and attenuator channels, known for their noise-adding properties, turns the Glauber-Sudarshan distribution of any input operator into its Wigner distribution, and its Wigner distribution into its Husimi distribution. As we dissect, the considered process, which can be performed in a quantum optical laboratory with relative ease, may be interpreted as realizing a quantum-to-classical transition.

We investigate the transport and entanglement properties exhibited by quantum walks with coin operators concatenated in a space-time fractal structure. Inspired by recent developments in photonics, we choose the paradigmatic Sierpinski gasket. The 0-1 pattern of the fractal is mapped into an alternation of the generalized Hadamard-Fourier operators. This two-state coin-operator approach overcomes the intricacies caused by the utilization of high-dimensional coin operators required in prior studies of discrete-time quantum walks on fractals. In fulfilling the blank space on the analysis of the impact of inhomogeneity in quantum walk properties, specifically, fractal deterministic inhomogeneity, our results show a robust effect of entanglement enhancement as well as an interesting road to superdiffusive spreading with a tunable scaling exponent attaining robust superdiffusion, subballistic though. Explicitly, with this fractal approach it is possible to obtain an increase in quantum entanglement with reduced impact on standard quantum walk theoretical spreading. Alongside those features, we analyze further properties such as the degree of interference and visibility. The present model corresponds to an application of fractals in an experimentally viable setting, namely, the building block for the construction of photonic patterned structures.

We present a simple proof of a sufficient condition for the uniqueness of nonequilibrium steady states of Gorini-Kossakowski-Sudarshan-Lindblad equations. We demonstrate the applications of the sufficient condition using examples of the transverse-field Ising model, the $XYZ$ model, and the tight-binding model with dephasing.

The Demkov-Kunike (DK) model, characterized by a time-dependent Rabi coupling $J\text{sech}(t/T)$ and on-site detuning ${\mathrm{\Delta }}_0+{\mathrm{\Delta }}_{1}tanh(t/T)$, has one of the most general forms of an exactly solvable two-state quantum system and therefore it provides a paradigm for coherent manipulations of a qubit's quantum state. Despite its extensive application in noise-free cases, the exploration of the noisy DK model remains limited. Here we extend the coherent DK model to take into account a noisy coupling term $J\to J_{\text{noisy}}\left(t\right)$. We consider colored Markovian noise sources represented by telegraph noise and Gaussian noise. We present exact solutions for the survival probability $Q_{\text{DK}}^{\text{noisy}}$ of the noisy DK model, namely, the probability of the system to remain in its initial state. For slow telegraph noise, we identify parameter regimes where the survival probability $Q_{\text{DK}}^{\text{noisy}}$ is suppressed rather than enhanced by noise. In contrast, for slow Gaussian noise, the noise always enhances the survival probability $Q_{\text{DK}}^{\text{noisy}}$, due to the absorption of noise quanta across the energy gap. This study not only complements the existing research on the noisy Landau-Zener model but also provides valuable insights into the control of two-level quantum systems.

In this paper, we construct orthogonal genuinely multipartite entangled bases in ${\left({\mathbb{C}}^3\right)}^{\otimes N}$ for $N\ge 3$, where every state is a one-uniform state. By modifying this construction, we successfully obtain strongly nonlocal orthogonal genuinely entangled sets and strongly nonlocal orthogonal genuinely entangled bases, which provide an answer to the problem raised by Halder et al. [Phys. Rev. Lett. 122, 040403 (2019)]. The strongly nonlocal orthogonal genuinely entangled set we constructed in ${\left({\mathbb{C}}^3\right)}^{\otimes N}$ contains much fewer quantum states than all known ones. Meanwhile, our results also answer the question given by Wang et al. [Phys. Rev. A 104, 012424 (2021)].

The no-cloning theorem is a cornerstone of quantum cryptography. Here we generalize and rederive in a unified framework various upper bounds on the maximum achievable fidelity of probabilistic and deterministic cloning machines. Building on ideas by Gisin [Phys. Lett. A 242, 1 (1998)], our result follows from the fact that remote state preparation is possible and the no-signaling principle holds. We apply our general theorem to several subsets of states that are of interest in quantum cryptography.

We classify different ways to passively protect classical and quantum information, i.e., we do not allow for syndrome measurements, in the context of local Lindblad models for spin systems. Within this family of models, we suggest that passive error correction is associated with nontrivial phases of matter and propose a definition for dissipative phases based on robust steady-state degeneracy of a Lindbladian in the thermodynamic limit. We study three thermalizing models in this context: the two-dimensional (2D) Ising model, the 2D toric code, and the 4D toric code. In the low-temperature phase, the 2D Ising model hosts a robust classical steady-state degeneracy, while the 4D toric code hosts a robust quantum steady-state degeneracy. We perturb the models with terms that violate detailed balance and observe that qualitative features remain unchanged, suggesting that ${\mathbb{Z}}_2$ symmetry breaking in a Lindbladian is useful to protect a classical bit while intrinsic topological order protects a qubit.