In this work, we carry out an comprehensive study for the electron scattering with atomic argon in the framework of relativistic box-variational method. The phase shifts first are extracted from relativistic coupled-cluster-theory calculations. Then the properties including total elastic, momentum transfer, viscosity cross sections, and differential cross sections are evaluated and compared with available

We theoretically study the light induced optical binding of one-dimensional photonic crystal composed of hyperbolic metamaterial and dielectric-photonic hypercrystal. It is shown that light can induce self-organization of hyperbolic slabs into one same stable photonic crystal at different angles of incidence-angle independent optical binding. In addition, self-organization of photonic hypercrystals

We report the observation of a parametric instability in the out-of-equilibrium steady state of two coupled Kerr microresonators coherently driven by a laser. Using a resonant excitation, we drive the system into an unstable regime, where we observe the appearance of intense and well resolved sideband modes in the emission spectrum. This feature is a characteristic signature of self-sustained oscillations

We consider the reflection from a random medium of light with short coherence length. We found that the second order correlation function of light can have a peak in a direction where the reflection angle is equal to angle of incidence. This occurs when the size of the region, from which light is collected, is larger than the coherence length.

The interplay of Anderson localisation and decoherence results in intricate dynamics that is notoriously difficult to simulate on classical computers. We develop the framework for a quantum simulation of such an open quantum system making use of time-varying randomised gradients, and show that even an implementation with limited experimental resources results in accurate simulations.

Spontaneous collapse models aim to resolve the measurement problem in quantum mechanics by considering the collapse of wave functions as a physical process. We analyze how these models affect a decaying flavor oscillating system whose evolution is governed by a phenomenological non-Hermitian Hamiltonian. In turn, we apply two popular collapse models, the QMUPL and the CSL models, to a neutral meson

State changing in thermal-energy collisions between strontium atoms in very-high-n, n∼300, n1F3 Rydberg states is studied. In collisions between Rydberg atoms the dipole-dipole interaction generates an effective electric field at each atom which triggers Stark precession and the evolution of their angular momenta, L. Such L-changing collisions are examined using both quantum and classical theory. The

We investigate a case of the Hu-Paz-Zhang master equation of the Caldeira-Leggett model without Lindblad-form obtained in the weak coupling limit up to the second order perturbation. In our study we use Gaussian initial states to be able to employ a sufficient and necessary condition, which can expose positivity violations of the density operator during the time evolution. We demonstrate that the evolution

The objective of this work is to derive approximate rovibrational selection rules for the interaction-induced molecular absorption in dipole-less polyatomic molecules. Taking a combination ν2+ν3 band in CO2 molecule as an example, we show that selection rules ΔJ=±1 are allowed in collision-induced absorption (CIA) along with conventional selection rules ΔJ=0,±2 characteristic for CIA in homonuclear

High-fidelity Bragg pulses are an indispensable tool for state-of-the-art atom interferometry experiments. In this work, we introduce an analytic theory for such pulses. Our theory is based on the pivotal insight that the physics of Bragg pulses can be accurately described by the adiabatic theorem. We show that efficient Bragg diffraction is possible with any smooth and adiabatic pulse shape and that

Key reconciliation of quantum key distribution (QKD) is the process of correcting errors caused by channel noise and eavesdropper. Reconciliation efficiency is the most important figure for judging the quality of a key reconciliation scheme. Single-matrix rate-compatible reconciliation (SRCR) scheme can access optimal reconciliation efficiency because of rate-compatible technologies, i.e., shortening

In the general case, upon free-space propagation of a paraxial optical vortex (OV) its topological charge (TC) is not conserved, unlike the orbital angular momentum (OAM), which remains unchanged. In this work, we discuss a Gaussian beam with fractional TC in the source plane, showing theoretically and numerically in which way the TC is changing (but remains integer) upon free-space propagation. There

Security of the perfect quantum key distribution protocol can be guaranteed by applying the fundamental laws of quantum mechanics, but the practical quantum key distribution system may be attacked by utilizing the imperfect state preparation and measurement devices. In this work, we analyze security of the practical quantum key distribution system with weak randomness basis selection, where the basis

This article presents a general master equation formalism for the interaction between travelling pulses of quantum radiation and localized quantum systems. Traveling fields populate a continuum of free space radiation modes and the Jaynes-Cummings model, valid for a discrete eigenmode of a cavity, does not apply. We develop a complete input-output theory to describe the driving of quantum systems by

Quantum mechanics allows the occurrence of events {} having any definite causal order. We show that the application of two different thermal channels in causally inseparable order can enhance the potential to extract work, in contrast to any of their definite order of occurrence. Surprisingly, this enhancement is possible even {} assigning any {} value to the input qubits. Further, we provide the first

We report the spectral features of a phase-shifted parity and time (𝒫𝒯)-symmetric fiber Bragg grating (PPTFBG) and demonstrate its functionality as a demultiplexer in the unbroken 𝒫𝒯-symmetric regime. The length of the proposed system is of the order of millimeters and the lasing spectra in the broken 𝒫𝒯-symmetric regime can be easily tuned in terms of intensity, bandwidth and wavelength by varying

To achieve the optimal phase sensitivity in two-mode interferometers, one key problem is how to distribute photons between the two input ports, given a fixed total average photon number. In both the 𝔰𝔲(2) and 𝔰𝔲(1,1) interferometers with a product of coherent and Fock states as inputs, we find there exists a critical value of the total photon number, below which the optimal phase sensitivity can

We study the Floquet-surface bound states embedded in the continuum (BICs) and bound states out the continuum (BOCs) in a resonantly driven 1D tilted defect-free lattice. In contrast to fragile single-particle BICs assisted by specially tailored potentials, we find that Floquet-surface BICs, stable against structural perturbations, can exist in a wide range of parameter space. By using a multiple-time-scale

Correlation self-testing of a theory addresses the question of whether we can identify the set of correlations realisable in a theory from its performance in a particular information processing task. Applied to quantum theory it aims to identify an information processing task whose optimal performance is achieved only by theories realising the same correlations as quantum theory. In an accompanying

Braiding defects in topological stabiliser codes has been widely studied as a promising approach to fault-tolerant quantum computing. Here, we explore the potential and limitations of such schemes in codes of all spatial dimensions. We prove that a universal gate set for quantum computing cannot be realised by supplementing locality-preserving logical operators with defect braiding, even in more than

Any nonclassical effect noticed in measured statistics is usually attributed just to the light state being observed. According to Born’s rule, quantum probabilities are given by the overlap between the system state and measurement states in a quite symmetrical way. We demonstrate that the nonclassicality of the measurement is a necessary condition to obtain nonclassical statistics. To this end, we

Quantum electrodynamical (QED) calculations of ionization energies of the 1sndD states are performed for the helium atom. We reproduce the previously known relativistic and QED effects up to order mα5 and extend the theory by calculating the complete mα6 correction. The total contribution of the mα6 effects is shown to be much smaller than previously estimated, due to a large cancellation between the

The bulk viscosity of two-component fermions with a zero-range interaction is revisited both in two and three dimensions. We first point out that the "standard’’ Kubo formula employed in recent studies has flaws to give rise to an unphysical divergent bulk viscosity even in a limit where it is supposed to vanish. The corrected Kubo formula as well as the sum rule is then carefully rederived so as to

The efficient circular-polarized terahertz (THz) emission is important for THz imaging technology and basic scientific research. In order for it, we have made a simple and all-passive design to achieve collinear and co-rotating circular-polarized two-color laser fields. The collinearity allows us to manipulate accurately the relative phase between two-color lasers. For a given relative phase, our experiments

Combining a laser vaporization cluster source, a velocity scan system, and a time-of-flight mass spectrometer, we measured velocity distributions of few-atom cobalt clusters (Con, n=6−60) suspended in a helium carrier gas and expanded into vacuum. The velocity distributions provide information about the cluster size dependence of the translational temperature, flow velocity, and velocity slip with

The projection method with explicitly correlated Gaussians is used to demonstrate the existence of two doubly excited states of the positronium molecule (Ps2). One is below the Ps(n=2) + Ps(n=2) threshold, with A1 symmetry, and the other is below the Ps(n=2) + Ps$(n=3) $ threshold, with E symmetry. These states exist as resonances in the Ps−Ps continuum. Moreover, the resonance positions and resonance

We present fully ab initio calculations of second-overtone rovibrational line shapes of carbon monoxide perturbed by argon. The quantum mechanical scattering problem between CO and Ar is solved numerically on two different ab initio interaction potentials. We use the generalized Hess method to determine spectroscopic cross sections which describe the effect of collisions on each spectral line. Using

When atoms or molecules are exposed to strong short-pulse infrared radiation, ionization as well as "frustrated tunneling ionization’’ (FTI) can occur, in which some of the nearly freed electrons recombine into the initial ground or an excited bound state. We analyze the ellipticity dependence of the relative signals that are predicted in a single-active electron approximation (SAE), the validity of

Recent advances in the study of synthetic dimensions revealed a possibility to employ the frequency space as an additional degree of freedom which allows for investigating and exploiting higher-dimensional phenomena in a priori low-dimensional systems. However, the influence of nonlinear effects on the synthetic frequency dimensions was studied only under significant restrictions. In the present paper

We theoretically demonstrate that an especially tuned degenerate optical parametric amplifier (OPA) inside a cavity can lead to the momentum squeezing of a moving membrane in a dissipative optomechanical system. The momentum squeezing of the membrane depends on the parametric gain and the parametric phase of the OPA, the power of the external laser driving the cavity, and the temperature of the environment

A time orbiting potential trap confines neutral atoms in a rotating magnetic field. The rotation of the field can be useful for precision measurements, since it can average out some systematic effects. However, the field is more difficult to characterize than a static field, and it makes light applied to the atoms have a time-varying optical polarization relative to the quantization axis. These problems

The characterization of errors in a quantum system is a fundamental step for two important goals. First, learning about specific sources of error is essential for optimizing experimental design and error correction methods. Second, verifying that the error is below some threshold value is required to meet the criteria of threshold theorems. We consider the case where errors are dominated by the generalized

In recent experiments with ultracold atoms, both two-dimensional (2d) Chern insulators and one-dimensional (1d) topological charge pumps have been realized. Without interactions, both systems can be described by the same Hamiltonian, when some variables are being reinterpreted. In this paper, we study the relation of both models when Hubbard interactions are added, using the density-matrix renormalization-group

In this work, we implement a scheme to combine six coherent, spatially separated Raman sidebands generated in single-crystal diamond into a collinear beam. With appropriate phase tuning, this results in a pulse much shorter than the generating pump. We elucidate the characteristics of the synthesized pulse by using an interferometric collinear cross-correlation frequency-resolved optical gating setup

We discuss the properties of bound states in finite-bandwidth waveguide QED beyond the Rotating Wave Approximation or excitation number conserving light-matter coupling models. Therefore, we extend the calculations to a broader range of light-matter strengths, in particular, in the so-called ultrastrong coupling regime. We do this using the Polaron technique. Our main results are as follows. We compute

The method of the laser pulse self-compression in the process of Raman scattering in a plasma created by a counter-propagating ionized pulse is considered. The sharpness of the ionization front ensures the formation of an output pulse close to the π-pulse solution with a sharp leading edge. The dependence of the gain increment on the transverse wave number leads to the formation of a smooth phase front

Hyperfine structure (HFS) of atomic energy levels arises due to interactions of atomic electrons with a hierarchy of nuclear multipole moments, including magnetic dipole, electric quadrupole and higher rank moments. Recently, a determination of the magnetic octupole moment of the 173Yb nucleus was reported from HFS measurements in neutral 173Yb [PRA 87, 012512 (2013)], and is four orders of magnitude

Hyper-hybrid entanglement for two indistinguishable bosons has been recently proposed by Li {et al.} [Phy. Rev. Lett, 120, 050404 (2018)]. In the current work, we show that this entanglement exists for two indistinguishable fermions also. Next, we establish two novel {} results: no hyper-hybrid entanglement for two {} particles, and no unit fidelity quantum teleportation using {} particles. If either

We investigate the stability and dynamics of the orbital angular momentum modes of a repulsive Bose-Einstein condensate trapped in two tunnel-coupled rings in a stack configuration. Within mean-field theory, we derive a two-state model for the system in the case in which we populate equally both rings with a single orbital angular momentum mode and include small perturbations in other modes. Analyzing

We construct a large family of Planar Maximally Entangled (PME) states which are a wider class of multi-partite entangled states than Absolutely Maximally Entangled (AME) states. These are states in which any half of the qudits are in a maximally mixed state, provided that they form a connected subset. We show that in contrast to AMEs, PMEs are easier to find and there are various PMEs for any even

Harmonic frequency combs, in which the lasing modes are separated by a period of tens of free spectral ranges from each other, have been recently discovered in quantum cascade lasers (QCLs). There is an ongoing debate how the harmonic combs can be formed and stable under continuous pumping. Here we reproduce the harmonic state of lasing in QCLs by space-time-domain numerical simulations and show that

In most experiments with atoms trapped in optical lattices, the transverse size of the optical lattice beams is on the order of tens of micrometers, and loading many atoms into smaller optical lattices has not been carefully investigated. We report trapping 1500 171Yb atoms in a one-dimensional optical lattice generated by a narrow cavity mode at a distance of 0.14 mm from a mirror surface. The simplest

The dissociation dynamics of LiH molecules induced by two overlapping femtosecond pulses are investigated based on the time-dependent quantum wave packet method. The first pulse induces population transfer from the ground state X1Σ+ to the excited state A1Σ+ which is coupled with the repulsive state B1Π and the state X1Σ+ by the second pulse. The two products Li(2p) and Li(2s) can be obtained via the

Quantum tomography is an essential experimental tool for testing any quantum technology implementation. Transverse spatial quantum states of light play a key role in many experiments in the field of quantum information as well as in free-space optical communications. In this paper we propose and experimentally demonstrate the tomography of spatial quantum states with a deformable mirror. It may be