We theoretically investigate the collisional heating of a cold atom system

subjected to time-periodic forces. We show within the Floquet framework that

this heating rate due to two-body collisions has a general semiclassical

expression $\mathcal{P}\propto \rho \sigma v_{\rm col} E_0$, depending on the

kinetic energy $E_0$ associated with the shaking, particle number density

$\rho$, elastic collision cross section $\sigma$, and an effective collisional

velocity $v_{\rm col}$ determined by the dominant energy scale in the system.

# All

We study bound-state solutions of the Klein-Gordon equation

$\varphi^{\prime\prime}(x) =\big[m^2-\big(E-v\,f(x)\big)^2\big] \varphi(x),$

for bounded vector potentials which in one spatial dimension have the form

$V(x) = v\,f(x),$ where $f(x)\le 0$ is the shape of a finite symmetric central

potential that is monotone non-decreasing on $[0, \infty)$ and vanishes as

$x\rightarrow\infty.$ Two principal results are reported. First, it is shown

that the eigenvalue problem in the coupling parameter $v$ leads to spectral

We consider online algorithms with respect to the competitive ratio. Here, we

investigate quantum and classical one-way automata with non-constant size of

memory (streaming algorithms) as a model for online algorithms. We construct

problems that can be solved by quantum online streaming algorithms better than

by classical ones in a case of logarithmic or sublogarithmic size of memory.

Optimal (reversible) processes in thermodynamics can be modelled as

step-by-step processes, where the system is successively thermalized with

respect to different Hamiltonians by an external thermal bath. However, in

practice interactions between system and thermal bath will take finite time,

and precise control of their interaction is usually out of reach. Motivated by

this observation, we consider finite-time and uncontrolled operations between

system and bath, which result in thermalizations that are only partial in each

We suggest implementation of quantum teleportation protocol of unknown qubit

beyond Bell states formalism. Hybrid entangled state composed of coherent

components that belong to Alice and dual-rail single photon at Bob disposal is

used. Nonlinear effect on the teleported state is realized due to peculiarity

of interaction of coherent components with discrete variable state on a beam

splitter. Bob performs unitary transformation after receiving the appropriate

In this paper, we present a quantum algorithm for dynamic programming

approach for problems on directed acyclic graphs (DAGs). The running time of

the algorithm is $O(\sqrt{\hat{n}m}\log \hat{n})$, and the running time of the

best known deterministic algorithm is $O(n+m)$, where $n$ is the number of

vertices, $\hat{n}$ is the number of vertices with at least one outgoing edge;

$m$ is the number of edges. We show that we can solve problems that use OR,

AND, NAND, MAX and MIN functions as the main transition steps. The approach is

Logical inference leads to one of the major interpretations of probability

theory called logical interpretation, in which the probability is seen as a

measure of the plausibility of a logical statement under incomplete

information. In this paper, assuming that our usual inference procedure makes

sense for every set of logical propositions represented in terms of commuting

projectors on a given Hilbert space, we extend the logical interpretation to

quantum mechanics and derive the Born rule. Our result implies that, from the

The condition of phase matching prohibits the transfer of excitation from

free-space photons to surface plasmon polaritons (SPP). We propose and analyze

a scheme that excites an ensemble of emitters in a collective state, which is

phase matched with the SPP by the optical pulses used for its preparation. By a

collective enhancement the ensemble, hence, emits an SPP in a well defined

direction. We demonstrate the scheme by analyzing the launching of

near-infrared graphene SPP. Our theory incorporates the dispersive and

In this paper, we study the dynamical behavior and quantum metrology in a

rotating Nitrogen-Vacancy(NV) center system which is subject to an external

magnetic field. Based on the recently realized rapid rotation of nano-rotor [J.

Ahn, et. al., Phys. Rev. Lett. 121, 033603 (2018) and R. Reimann, et. al.,

Phys. Rev. Lett. 121, 033602 (2018)], the frequency of the rotation is close to

that of the intrinsic frequency of the NV center system, we predict the quantum

In this Letter, we experimentally demonstrate the first realization of weak

value amplification (WVA) using purely atomic degrees of freedom. Our

measurement model identifies the internal electronic states and external

motional states of a single trapped $^{40}$Ca$^+$ ion as the system degree and

pointer degree respectively, and their controllable weak coupling is provided

by a bichromatic light field. By performing appropriate postselection on the

internal states, a tiny position displacement of 4 angstroms of the trapped ion