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In this paper, we propose a scheme of a long-lived broadband superefficient

multiresonator quantum memory in which a common resonator is connected with an

external waveguide and with a system of high-quality miniresonators containing

long-lived resonant electron spin ensembles. The scheme with 4 miniresonators

has been analyzed in details and it was shown that it is possible to store an

input broadband signal field to the electron spin ensembles with quantum

We present a blueprint for building a fault-tolerant universal quantum

computer with Rydberg atoms. Our scheme, which is based on the surface code,

uses individually-addressable optically-trapped atoms as qubits and exploits

electromagnetically induced transparency to perform the multi-qubit gates

required for error correction and computation. We discuss the advantages and

challenges of using Rydberg atoms to build such a quantum computer, and we

perform error correction simulations to obtain an error threshold for our

A common viewpoint is that a particle could be quantum entangled with another

particle arbitrarily far away. But in this paper we suggest that there is an

utmost distance for the existence of quantum entanglement between two

particles, beyond which the initial quantum entanglement would be broken by

some quantum gravitational effect. The utmost distance is proposed to be

$L_{QE}=\lambda^\alpha l_{p}^{1-\alpha}$, where $\lambda$ is the quantum

wavelength of the particles and $l_{p}= 1.616 \times 10^{-35} m$ is the Planck

We theoretically propose and investigate a feasible experimental scheme for

the realization of the dynamical Casimir effect (DCE) in a hybrid

optomechanical cavity with a moving end mirror containing an interacting

cigar-shaped Bose-Einstein condensate (BEC). We show that in the red-detuned

regime of cavity optomechanics together with the weak optomechanical coupling

limit by \textit{coherent} modulation of the \textit{s}-wave scattering

frequency of the BEC and the mechanical spring coefficient of the mechanical

The time evolution of periodically driven non-Hermitian systems is in general

non-unitary but can be stable. It is hence of considerable interest to examine

the adiabatic following dynamics in periodically driven non-Hermitian systems.

We show in this work the possibility of piecewise adiabatic following

interrupted by hopping between instantaneous system eigenstates. This

phenomenon is first observed in a computational model and then theoretically

explained, using an exactly solvable model, in terms of the Stokes phenomenon.

A communication game consists of distributed parties attempting to jointly

complete a task with restricted communication. Such games are useful tools for

studying limitations of physical theories. A theory exhibits preparation

contextuality whenever its predictions cannot be explained by a preparation

noncontextual model. Here, we show that communication games performed in

operational theories reveal the preparation contextuality of that theory. For

statistics obtained in a particular family of communication games, we show a

We compare two approaches to refine the "linear model" of cavity

optomechanics, in order to describe radiation pressure effects that are beyond

first order in the coupling constant. We compare corrections derived from (I) a

widely used phenomenological Hamiltonian that conserves the photon number and

(II) a two-mode truncation of C. K. Law's microscopic model, which we take as

the "true" Hamiltonian of the system. While these approaches agree at first

order, the latter model does not conserve the photon number, resulting in

- Read more about Exploring corrections to the Optomechanical Hamiltonian. (arXiv:1711.06688v1 [quant-ph])
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In this work, we investigate the heat exchange between two quantum systems

whose initial equilibrium states are described by the generalized Gibbs

ensemble. First, we generalize the fluctuation relations for heat exchange

discovered by Jarzynski and W\'ojcik to quantum systems prepared in the

equilibrium states described by the generalized Gibbs ensemble at different

generalized temperatures. Second, we extend the connections between heat

exchange and R\'enyi divergences to quantum systems with very general initial

In a bipartite set-up, the vacuum state of a free Bosonic scalar field is

entangled in real space and satisfies the area-law--- entanglement entropy

scales linearly with area of the boundary between the two partitions. In this

work, we show that the area law is violated in two spatial dimensional model

Hamiltonian having dynamical critical exponent z=3. The model physically

corresponds to next-to-next-to-next nearest neighbour coupling terms on a

lattice. The result reported here is the first of its kind of violation of area

We generalize the recently proposed resource theory of coherence (or

superposition) [Baumgratz, Cramer & Plenio, Phys. Rev. Lett. 113:140401; Winter

& Yang, Phys. Rev. Lett. 116:120404] to the setting where not only the free

("incoherent") resources, but also the objects manipulated are quantum

operations, rather than states. In particular, we discuss an information

theoretic notion of coherence capacity of a quantum channel, and prove a

single-letter formula for it in the case of unitaries. Then we move to the