It is very common in the literature to write a Markovian quantum master equation in Lindblad form to describe a system with multiple degrees of freedom and weakly connected to multiple thermal baths which can, in general, be at different temperatures and chemical potentials. However, the microscopically derived quantum master equation up to leading order in a system-bath coupling is of the so-called Redfield form, which is known to not preserve complete positivity in most cases. Additional approximations to the Redfield equation are required to obtain a Lindblad form. We lay down some fundamental requirements for any further approximations to the Redfield equation, which, if violated, leads to physical inconsistencies such as inaccuracies in the leading order populations and coherences in the energy eigenbasis, violation of thermalization, and violation of local conservation laws at the nonequilibrium steady state. We argue that one or more of these conditions will generically be violated in all the weak system-bath-coupling Lindblad descriptions existing in the literature to our knowledge. As an example, we study the recently derived universal Lindblad equation and use these conditions to show the violation of local conservation laws due to inaccurate coherences but accurate populations in the energy eigenbasis. Finally, we exemplify our analytical results numerically in an interacting open quantum spin system.

It is well known that fringe contrast is not a good quantifier of the wave nature of a quanton in multipath interference. An alternative interference visibility, based on the Hilbert-Schmidt coherence is introduced. It is demonstrated that this visibility is a good quantifier of wave nature and can be experimentally measured. A generalized path predictability is introduced, which reduces to the predictability of Greenberger and Yasin for the case of two paths. In a multipath, which-way interference experiment, the new visibility, the predictability, and the $I$ concurrence (quantifying the entanglement between the quanton and the path detector) are shown to follow a tight triality relation. It quantifies the essential role that entanglement plays in multipath quantum complementarity.

We propose to measure line profiles and angular distributions of the radiative-electron-capture transition in collisions of sub-MeV/$u {\mathrm{Ar}}^{18+}$ with helium. We estimate the line profile and the angular distribution using hydrogenlike and Hartree-Fock wave functions and show that the asymmetry of the line profile and the deviation of the angular distribution from the ${sin}^2{\theta }_{\mathrm{t}}$ law are magnified in the sub-MeV/$u$ region. Finite detector resolution and ion-beam monochromaticity are considered, and the results show that by using a usual bent-crystal spectrometer and a group of commercial silicon drift x-ray detectors one will be able to obtain sufficiently precise line profile and angular distribution to distinguish different theoretical descriptions of target atoms. The enhanced sensitivity to different theoretical approaches at low energies suggests that the proposed experiment will provide insights into the electromagnetic transition of an electron between a pair of relatively moving nuclei.

We study the influence of the rotations and vibrations of the symmetric-top ${\mathrm{RaOCH}}_3$ molecule on its effectiveness as a probe for the $\mathcal{P}, \mathcal{T}$-violating effects, such as the electron electric dipole moment and the scalar-pseudoscalar electron-nucleon interaction. The corresponding enhancement parameters $E_{\mathrm{eff}}$ and $E_{\mathrm{s}}$ are computed for the ground and first excited rovibrational states with different values of the angular momentum component $K$. For the lowest $K$ doublet with $v_{\perp }=0$ and $K=1$ the values are $E_{\mathrm{eff}}=47.647\mathrm{GV}/\mathrm{cm}$ and $E_{\mathrm{s}}=62.109\mathrm{kHz}$. The results show larger deviation from the equilibrium values than in triatomic molecules.

Here we report measured and calculated values of decay rates of the $3d^4\left({}^{5}D\right)4s4p\left({}^{3}P^o\right)y{}^{7}P_{2,3,4}^o$ states of Cr i. The decay rates are measured using time-correlated single-photon counting with roughly 1% total uncertainty. In addition, the isotope shifts for transitions between these states and the ground state are measured by laser induced fluorescence to roughly 0.5% uncertainty. The decay rate calculations are carried out by a hybrid approach that combines configuration interaction and the linearized coupled-cluster method ($\mathrm{CI}+$all-order method). The measurements provide a much needed precision benchmark for testing the accuracy of the $\mathrm{CI}+$all-order approach for such complicated systems with six valence electrons, allowing us to significantly expand its applicability. These measurements also demonstrate operation of a cryogenic buffer gas beam source for future cold molecule experiments.

The francium atom is considered as a prospective candidate system to search for the $\mathcal{T},\mathcal{P}$-violating electron electric dipole moment [Aoki et al., Quantum Sci. Technol. 6, 044008 (2021)]. We demonstrate that the same experiment can be used for axionlike particles (ALP) search. For this, we calculate electronic structure constants of the ALP-mediated interaction for a wide range of ALP masses. Using the recently updated constraints on products of ALP-electron and ALP-nucleon coupling constants, we show that contribution of considered interactions corresponding to these constraints can give significant contribution to the atomic electric dipole moment. Therefore, obtainment of stronger restrictions for ALP characteristics in the francium atom electric dipole moment experiment is possible.

Topological phases of ultracold atoms recently have been intensively studied in both optical superlattices and Raman lattices. However, the topological features induced by the interplay between such two lattices remain largely unexplored. Here we present an optical Raman superlattice system that incorporates an optical superlattice and a Raman superlattice. The Raman superlattice presented here supports tunable dimerized spin-orbit couplings and staggered on-site spin flips. We find that such a system respects a spin-rotation symmetry and has much richer topological properties. Specifically, we show that various topological phases could emerge in the optical Raman superlattice, such as four different chiral topological insulator phases and two different quantum spin Hall insulator phases, identified by spin winding and spin Chern numbers, respectively. We also demonstrate that the spin-dependent topological invariants could be directly measured by quench dynamics.

The noise-induced coherence created via the quantum interference of incoherent radiation in atomic three-level systems of V and Λ types driven by a pair of weak laser pulses is shown to result in exchange of optical vortices. In the three- level V-type atom-light coupling the system is populated in its ground level, while in the Λ model the system is initially prepared in an electromagnetically induced transparency state. By solving the quantum optical Maxwell-Bloch equations and with quantum interference of incoherent radiation present, we show that the orbital angular momentum (OAM) of the vortex probe beam can be transferred to a generated signal field. While the exchange efficiency in the V configuration is higher, the losses are less in the Λ scheme when we consider such a noise-induced coherence. We further discuss the effects of phase mismatching and inhomogeneous broadening on the energy conversion between light beams carrying OAM.

Quantum systems of high dimensions are attracting a lot of attention because they feature interesting properties when it comes to observing entanglement or other forms of correlations. In particular, their improved resistance to noise is favorable for experiments in quantum communication or quantum cryptography. However, witnessing this high-dimensional nature remains challenging, especially when the assumptions on the parties involved are weak, typically when one of them is considered as a black box. In this context, the concept of genuine high-dimensional steering has been recently introduced and experimentally demonstrated [Phys. Rev. Lett. 126, 200404 (2021)]; it allows for a one-sided device-independent certification of the dimension of a bipartite shared state by only using two measurements. Here I overcome this limitation by developing, for more than two measurements, universal bounds on the incompatibility robustness, turned into meaningful dimension certificates. Interestingly, even though the resulting bounds are quite loose, they still often offer an increased resistance to noise and could then be advantageously employed in experiments.

We apply the inverse geometric optimization technique to generate an optimal and robust stimulated Raman exact passage (STIREP) considering the loss of the upper state as a characterization parameter. Control field temporal shapes that are optimal with respect to pulse area, energy, and duration are found to form a simple sequence with a combination of intuitively (near the beginning and the end) and counterintuitively ordered pulse pairs. The resulting dynamics produces a loss which is about a third of that of the nonrobust optimal STIREP. Alternative optimal solutions featuring lower losses, larger pulse areas, and fully counterintuitive pulse sequences are derived.

The derivation of leading quantum electrodynamic corrections to the nuclear magnetic shielding in light hydrogen- and heliumlike atomic systems is described in detail. The presented theoretical approach applies to any light atomic and molecular systems, enabling the determination of the magnetic moment of light nuclei with much higher precision than known presently.

The electron-impact excitation from the ground state to the autoionizing level $1s2s^{2}2p_{1/2}J=1$ and the subsequent nonradiative Auger decay $1s2s^{2}2p_{1/2}J=1\to 1s^{2}2sJ=1/2$ of Be-like ions have been studied by using the multiconfigurational Dirac-Fock method and the relativistic distorted-wave theory. Special attention has been paid to the effect of the Breit interaction on the angular distribution of the Auger electrons emitted. To do so, the partial cross sections, alignment parameters of the autoionizing level, and intrinsic anisotropy parameters of the Auger decay are evaluated for Be-like ${\mathrm{Mg}}^{8+}, {\mathrm{Fe}}^{22+}, {\mathrm{Mo}}^{38+}, {\mathrm{Nd}}^{56+}, {\mathrm{Au}}^{75+}$, and ${\mathrm{U}}^{88+}$ ions, from which the angular distribution of the Auger electrons is further obtained. It is found that the Breit interaction hardly contributes to the angular distribution for low-$Z$ ions such as ${\mathrm{Mg}}^{8+}$, especially at low impact energies, while for medium- and high-$Z$ ions the situation becomes fairly different. To be specific, the Breit interaction contributes to lowering the anisotropy of the angular distribution, which first becomes quickly more prominent with increasing atomic number up to certain high-$Z$ ions and then behaves very slowly less prominently for higher-$Z$ ions. Moreover, for high-$Z$ ions the effect of the Breit interaction on the angular distribution is found to be nearly independent of the atomic number $Z$. Owing to opposite effects of the Breit interaction on the alignment parameters and the intrinsic anisotropy parameters, such an “abnormal behavior” is speculated to be caused very likely by a “competition” between the opposite effects of the Breit interaction on both of them.

We present a realization of a magneto-optical trap of mercury atoms on the ${}^{1}S_0\to {}^{3}P_1$ intercombination line. We report on trapping of all stable mercury isotopes. We characterize the effect of laser detuning, laser intensity, and gradient field on the trapping performance of our system. The atom number for the most abundant isotope ${}^{202}\mathrm{Hg}$ is $5\times {10}^7$ atoms. Moreover, we study the difference in cooling processes for bosonic and fermionic isotopes. We observe agreement with the Doppler cooling theory for the bosonic species and show sub-Doppler cooling for the fermionic species. We reach a phase-space density of a few parts in ${10}^{-7}$, which constitutes a promising starting condition for dipole trap loading and evaporative cooling.

Energy transport in low-dimensional systems or systems with long-range interactions shows unusual properties not observed in conventional three-dimensional materials. Trapped linear ion chains have been proposed as an ideal platform to study such phenomena, but many predicted features have not been demonstrated yet and the existing experiments mainly focus on the weak excitation limit where the dynamics can be described by linearized phonon modes. Here, we study the energy transport in a chain of ${}^{174}\mathrm{Yb}^{+}$ ions using a focused heating laser beam. Nontrivial effects are observed such as a nonmonotonic energy distribution with reflection symmetry, oscillatory heating dynamics, and a change in the heating pattern due to the competition between the external driving and interion coupling. Our work deepens the understanding about transport in low-dimensional systems and also provides guidelines for the sympathetic cooling of long ion chains, with applications in quantum information processing and precision measurement.

Wave functions, phase shifts, and corresponding elastic cross sections are investigated for two short-range interacting particles in a deformed external oscillator field. For this we use the equivalent $d$ method employing a noninteger dimension $d$. Using a square-well potential, we derive analytic expressions for scattering lengths and phase shifts. In particular, we consider the dimension, $d_E$, for infinite scattering length, where the Efimov effect occurs by addition of a third particle. We give explicitly the equivalent continuum wave functions in $d$ and ordinary three-dimensional space, and show that the phase shifts are the same in both methods. Consequently the $d$ method can be used to obtain low-energy two-body elastic cross sections in an external field.

We study the quantum dynamics of a peculiar driven system, a Bose gas subjected to periodically kicked interactions. In the limit of infinitely short kicks, this system was recently shown to exhibit a fast exponential spreading of the wave function. Here we examine this problem for kicks or arbitrary duration and show that, in this case, the spreading is not exponential but rather subdiffusive at long time. This phenomenon stems from the competition between the kinetic and interaction energies within the kicks, which is absent in the limit of delta kicks. Our analysis further shows that the breakdown of exponential spreading occurs at relatively short times even for extremely short kicks, suggesting that, in practice, subdiffusion should be more the rule than the exception in this system.

We propose a method for a control of turbulence by modifying the excitation cascade leading to turbulence. The method is based on the asymmetric coupling between the spatiotemporal excitation modes by non-Hermitian potentials. The non-Hermitian potentials are recently known to enable unidirectional coupling between modes. We demonstrate that such unidirectional coupling towards larger (smaller) wave numbers can increase (reduce) the energy flow in turbulent states, and therefore, influence the character of turbulence. The study is based on the complex Ginzburg-Landau equation, a universal model for pattern formation and turbulence in a wide range of systems including nonlinear optical resonators. We show that enhancement or reduction of turbulence is indeed dependent on the imposed direction of the energy flow, controlled by the phase shift between the real and imaginary parts of the temporal oscillation of the non-Hermitian potential.

In a hybrid scheme, consisting of a three-level atom-cavity-oscillator system, we show that synchronization [J. Czartowski, R. Müller, K. Życzkowski, and D. Braun, Phys. Rev. A 104, 012410 (2021)] and transfer of nonclassical states between the mechanical oscillator and the cavity field is possible. In this framework, we show that an initially thermalized mechanical oscillator, when connected to a squeezed bath, evolves to a squeezed state which in steady state is synchronized with the cavity mode. On the other hand, if the mechanical oscillator is initially prepared in a nonclassical state, e.g., squeezed and Schrödinger's cat states, while the cavity is in a thermal state, then a periodic transfer between the mechanical oscillator and cavity mode occurs for given interaction times. As qualitative results, we prove that the synchronization and transfer of the quantum states are feasible with high fidelity.

The nondipole under-the-barrier dynamics of the electron during strong-field tunneling ionization is investigated, examining the role of the Coulomb field of the atomic core. The common analysis in the strong-field approximation is consequently generalized to include the leading light-front nondipole Coulomb corrections and demonstrates the counterintuitive impact of the sub-barrier Coulomb field. Despite its attractive nature, the sub-barrier Coulomb field increases the photoelectron nondipole momentum shift along the laser propagation direction, involving a strong dependence on the laser field. The scaling of the effect with respect to the principal quantum number and angular momentum of the bound state is found. We demonstrate that the signature of Coulomb induced sub-barrier effects can be identified in the asymptotic photoelectron momentum distribution via a comparative study of the field-dependent longitudinal momentum shift for different atomic species with state-of-the-art experimental techniques of midinfrared lasers.