All

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

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