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We report nonclassical aspects of the collective behaviour of two atoms in a

cavity by investigating the photon statistics and photon distribution in a very

broad domain of parameters. Starting with the dynamics of two atoms radiating

in phase into the cavity, we study the photon statistics for arbitrary

interatomic phases as revealed by the second-order intensity correlation

function at zero time $g^{(2)}(0)$ and the Mandel $Q$ parameter. We find that

the light field can be tuned from antibunched to (super-)bunched as well as

Recent progress in integrated-optics technology has made photonics a

promising platform for quantum networks and quantum computation protocols.

Integrated optical circuits are characterized by small device footprints and

unrivalled intrinsic interferometric stability. Here, we take advantage of

femtosecond-laser-written waveguides' ability to process polarization-encoded

qubits and present the first implementation of a heralded controlled-NOT gate

on chip. We evaluate the gate performance in the computational basis and a

In the paper, a value assignment for projection operators relating to a

quantum system is equated with assignment of truth-values to the propositions

associated with these operators. In consequence, the Kochen-Specker theorem

(its localized variant, to be exact) can be treated as the statement that a

logic of those projection operators does not obey the principle of bivalence.

This implies that such a logic has a gappy (partial) semantics or many-valued

semantics.

Gauge-invariance is a fundamental concept in physics---known to provide the

mathematical justification for all four fundamental forces. In this paper, we

provide discrete counterparts to the main gauge theoretical concepts, directly

in terms of Cellular Automata. More precisely, we describe a step-by-step

gauging procedure to enforce local symmetries upon a given Cellular Automaton.

We apply it to a simple Reversible Cellular Automaton for concreteness. From a

Let V be a linear subspace of M_n(C) which contains the identity matrix and

is stable under Hermitian transpose. A "quantum k-clique" for V is a rank k

orthogonal projection P in M_n(C) for which dim(PVP) = k^2, and a "quantum

k-anticlique" is a rank k orthogonal projection for which dim(PVP) = 1. We give

upper and lower bounds both for the largest dimension of V which would ensure

the existence of a quantum k-anticlique, and for the smallest dimension of V

which would ensure the existence of a quantum k-clique.

We study a quantum Stirling cycle which extracts work using quantized energy

levels. The work and the efficiency of the engine depend on the length of the

potential well, and the Carnot efficiency is achieved in a low temperature

limiting case. We show that the lack of information about the position of the

particle inside the potential well can be converted into useful work without

resorting to any measurement. In the low temperature limit, we calculate the

Author(s): Thai M. Hoang, Rui Pan, Jonghoon Ahn, Jaehoon Bang, H. T. Quan, and Tongcang Li

Motion measurements of a nanosized bead—held aloft in an optical trap—confirm thermodynamic theories that describe fluctuations of microscopic objects.

[Phys. Rev. Lett. 120, 080602] Published Thu Feb 22, 2018

The dynamical relaxation and scaling properties of three different variants of the contact process

in two spatial dimensions are analysed. Dynamical contact processes capture a variety of contagious

processes such as the spreading of diseases or opinions. The universality of both local and global

two-time correlators of the particle-density and the associated linear responses are tested through

several scaling relations of the non-equilibrium exponents and the shape of the associated scaling

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Herein we continue the study of the representation theory of the algebra of permutation operators

acting on the ##IMG## [http://ej.iop.org/images/1751-8121/51/12/125202/aaaad15ieqn001.gif] {$n$}

-fold tensor product space, partially transposed on the last subsystem. We develop the concept of

partially reduced irreducible representations, which allows us to significantly simplify previously

Graph states have been used to construct quantum error correction codes for independent errors.

Hypergraph states generalize graph states, and symmetric hypergraph states have been shown to allow

for the correction of correlated errors. In this paper, it is shown that symmetric hypergraph states

are not useful for the correction of independent errors, at least for up to 30 qubits. Furthermore,

error correction for error models with protected qubits is explored. A class of known graph codes