The field of optomechanics provides us with several examples of quantum
photon-phonon interface. In this paper, we theoretically investigate the
generation and manipulation of quantum correlations in a microfabricated
optomechanical array. We consider a system consisting of localized photonic and
phononic modes interacting locally via radiation pressure at each lattice site
with the possibility of hopping of photons and phonons between neighboring
sites. We show that such an interaction can correlate various modes of a driven

We present a new method to compute short-time expectation values in large
collective spin systems with generic Markovian decoherence. Our method is based
on a Taylor expansion of a formal solution to the equations of motion for
Heisenberg operators. This expansion can be truncated at finite order to obtain
virtually exact results at short times that are relevant for metrological
applications such as spin squeezing. In order to evaluate the expansion for
Heisenberg operators, we compute the relevant structure constants of a

In support of the growing interest in quantum computing experimentation,
programmers need new tools to write quantum algorithms as program code.
Compared to debugging classical programs, debugging quantum programs is
difficult because programmers have limited ability to probe the internal states
of quantum programs; those states are difficult to interpret even when
observations exist; and programmers do not yet have guidelines for what to
check for when building quantum programs. In this work, we present quantum

Optical levitation of nanoscale particles has emerged as a platform for
precision measurement. Extremely low damping, together with optical
interferometric position detection, makes possible exquisite force measurement
and promises low-energy tests of fundamental physics. Essential to such
measurement is an understanding of the confidence with which parameters can be
inferred from spectra estimated from the indirect measurement provided by
interferometry. We present an apparatus optimized for sensitivity along one

We theoretically investigate the spectral property of a biphoton state from
multiplexed thermal atomic ensembles. This biphoton state originates from the
cascade emissions, which can be generated by two weak pump fields under
four-wave mixing condition. Under this condition, a signal photon from the
upper transition, chosen in a telecommunication bandwidth, can be generated
along with a correlated idler photon from the lower infrared transition. We can
spectrally shape the biphoton state by multiplexing the atomic ensembles with

We notice that the general PT-symmetric Hamiltonian matrix(N=2) having 6-real
parameters fails to reproduce one parameter PT-symmetric matrix.

Any quantum communication task requires a common reference frame (i.e. phase,
coordinate system). In particular, Quantum Key Distribution requires different
bases for preparation and measurements of states which are obviously based on
the existence of a common frame of reference. Here we show how QKD can be
achieved in the absence of any common frame of reference. We study the
coordinate reference frame, where the two parties do not even share a single
direction, but the method can be generalized to other general frames of

We propose an unconventional scheme for quantum entangled state distribution
(QESD) and quantum state transfer~(QST) based on a fiber-cavity-atom system, in
which three atoms are confined, respectively, in three bimodal cavities
connected with each other by optical fibers. The key feature of the scheme is
the virtual excitation of photons, which yields QESD and QST between the two
atoms in the edge-cavities conditioned on one-step operation only on the atom

Alignment is a geometric relation between pairs of Weyl-Heisenberg SICs, one
in dimension $d$ and another in dimension $d(d-2)$, manifesting a well-founded
conjecture about a number-theoretical connection between the SICs. In this
paper, we prove that if $d$ is even, the SIC in dimension $d(d-2)$ of an
aligned pair can be partitioned into $(d-2)^2$ tight $d^2$-frames of rank
$d(d-1)/2$ and, alternatively, into $d^2$ tight $(d-2)^2$-frames of rank
$(d-1)(d-2)/2$. The corresponding result for odd $d$ is already known, but the

The relative entropy is a measure of the distinguishability of two quantum
states. A great deal of progress has been made in the study of the relative
entropy between an excited state and the vacuum state of a conformal field
theory (CFT) reduced to a spherical region. For example, when the excited state
is a small perturbation of the vacuum state, the relative entropy is known to
have a universal expression for \textit{all} CFT's
\cite{Faulk-GR-entanglement}. Specifically, the perturbative relative entropy