All

We provide a study of various quantum phase transitions occurring in the XY
Heisenberg chain in a transverse magnetic field using the Meyer-Wallach (MW)
measure of (global) entanglement. Such a measure, while being readily
evaluated, is a multipartite measure of entanglement as opposed to more
commonly used bipartite measures. Consequently, we obtain analytic expression
of the measure for finite-size systems and show that it can be used to obtain
critical exponents via finite-size scaling with great accuracy for the Ising

Hereunder we continue the study of the representation theory of the algebra
of permutation operators acting on the $n$-fold tensor product space, partially
transposed on the last subsystem. We develop the concept of partially reduced
irreducible representations, which allows to simplify significantly previously
proved theorems and what is the most important derive new results for
irreducible representations of the mentioned algebra. In our analysis we are

Collinear antiferromagnets (AFs) support two degenerate magnon excitations
carrying opposite spin polarizations, by which magnons can function as
electrons in spin transport. We explore the interlayer coupling mediated by
antiferromagnetic magnons in an insulating ferromagnet (F)/AF/F trilayer
structure. The internal energy of the AF depends on the orientations of the two
Fs, which manifests as effective interlayer interactions JS1.S2 and K(S1.S2)^2.
Both J and K are functions of temperature and the AF thickness. Interestingly,

We demonstrate a Bayesian quantum game on an ion trap quantum computer with
five qubits. The players share an entangled pair of qubits and perform
rotations on their qubit as the strategy choice. Two five-qubit circuits are
sufficient to run all 16 possible strategy choice sets in a game with four
possible strategies. The data are then parsed into player types randomly in
order to combine them classically into a Bayesian framework. We exhaustively
compute the possible strategies of the game so that the experimental data can

An extension of the input-output relation for a conventional Michelson
interferometric gravitational-wave detector is carried out to treat an
arbitrary coherent state for the injected optical beam. This extension is one
of necessary researches toward the clarification of the relation between
conventional gravitational-wave detectors and a simple model of a
gravitational-wave detector inspired by weak-measurements in [A.~Nishizawa,
Phys. Rev. A {\bf 92} (2015), 032123.]. The derived input-output relation

We study the "anti-Unruh effect" for an entangled quantum state in reference
to the counterintuitive cooling previously pointed out for an accelerated
detector coupled to the vacuum. We show that quantum entanglement for an
initially entangled (spacelike separated) bipartite state can be increased when
either a detector attached to one particle is accelerated or both detectors
attached to the two particles are in simultaneous accelerations. However, if

Bloch oscillations in a single Josephson junction in the phase-slip regime
relate current to frequency. They can be measured by applying a periodic drive
to a DC-biased, small Josephson junction. Phase-locking between the periodic
drive and the Bloch oscillations then gives rise to steps at constant current
in the I-V curves, also known as dual Shapiro steps. Unlike conventional
Shapiro steps, a measurement of these dual Shapiro steps is impeded by the
presence of a parasitic capacitance. This capacitance shunts the junction

We explore ways to use the ability to measure the populations of individual
magnetic sublevels to improve the sensitivity of magnetic field measurements
and measurements of atomic electric dipole moments (EDMs). When atoms are
initialized in the $m=0$ magnetic sublevel, the shot-noise-limited uncertainty
of these measurements is $1/\sqrt{2F(F+1)}$ smaller than that of a Larmor
precession measurement. When the populations in the even (or odd) magnetic
sublevels are combined, we show that these measurements are independent of the

We propose a simple architecture for a scalable quantum network, in which the
quantum nodes consist of qubit systems confined in cavities. The nodes are
deterministically coupled by transmission and reflection of photons, which are
disentangled from the qubits at the end of each operation. A single photon can
generate an entangling controlled phase (C-PHASE) gate between any selected
number of qubits in the network and forms the basis for universal quantum

A double-slit experiment with entangled photons is theoretically analyzed. It
is shown that, under suitable conditions, two entangled photons of wavelength
$\lambda$ can behave like a \emph{biphoton} of wavelength $\lambda/2$. The
interference of these biphotons, passing through a double-slit can be obtained
by detecting both photons of the pair at the same position. This is in
agreement with the results of an earlier experiment. More interestingly, we