All

We investigate ground state properties of spin-1 bosonic system trapped in
optical lattice with extended standard basis operator (SBO) method. For both
ferromagnetic ($U_2<0$) and antiferromagnetic ($U_2>0$) systems, we
analytically figure out the symmetry properties in Mott-insulator and
superfluid phases, which would provide a deeper insight into the MI-SF phase
transition process. Then by applying self-consistent approach to the method, we
include the effect of quantum and thermal fluctuations and derive the MI-SF

Communication over a noisy channel is often conducted in a setting in which
different input symbols to the channel incur a certain cost. For example, for
the additive white Gaussian noise channel, the cost associated with a real
number input symbol is the square of its magnitude. In such a setting, it is
often useful to know the maximum amount of information that can be reliably
transmitted per cost incurred. This is known as the capacity per unit cost. In

With the Lipkin-Meshkov-Glick (LMG) model as an illustration, we construct a
thermodynamic cycle composed of two isothermal processes and two isomagnetic
field processes and study the thermodynamic performance of this cycle
accompanied by the quantum phase transition (QPT). We find that for a finite
particle system working below the critical temperature, the efficiency of the
cycle is capable of approaching the Carnot limit when the external magnetic
field \lambda_{1} corresponding to one of the isomagnetic processes reaches the

We demonstrate a synchronized readout (SR) technique for spectrally selective
detection of oscillating magnetic fields with sub-millihertz resolution, using
coherent manipulation of solid state spins. The SR technique is implemented in
a sensitive magnetometer (~50 picotesla/Hz^(1/2)) based on nitrogen vacancy
(NV) centers in diamond, and used to detect nuclear magnetic resonance (NMR)
signals from liquid-state samples. We obtain NMR spectral resolution ~3 Hz,

We study the unidirectional amplification of optical probe fields in a
three-mode optomechanical system, where the mechanical resonator interacts with
two linearly-coupled optical cavities and the cavities are driven by strong
optical pump fields. An optical probe field is injected into one of the cavity
modes, and at the same time, it is applied to the mechanical mode after being
down-converted by the optical pump frequency. We show that the transmission of

This paper presents a new measure of entanglement which can be employed for
multipartite entangled systems. The classification of multipartite entangled
systems based on this measure is considered. Two approaches to applying this
measure to mixed quantum states are discussed.

We propose a bosonic Josephson junction (BJJ) in two nonlinear mechanical
resonator coupled through two-phonon exchange interaction induced by quadratic
optomechanical couplings. The nonlinear dynamic equations and effective
Hamiltonian are derived to describe behaviors of the BJJ. We show that the BJJ
can work in two different dynamical regimes: Josephson oscillation and
macroscopic self-trapping. The system can transfer from one regime to the other
one when the self-interaction and asymmetric parameters exceed their critical

In recent years, the study of heat to work conversion has been re-invigorated
by nanotechnology. Steady-state devices do this conversion without any
macroscopic moving parts, through steady-state flows of microscopic particles
such as electrons, photons, phonons, etc. This review aims to introduce some of
the theories used to describe these steady-state flows in a variety of
mesoscopic or nanoscale systems. These theories are introduced in the context
of idealized machines which convert heat into electrical power (heat-engines)

We consider two chains, each made of $N$ independent oscillators, immersed in
a common thermal bath and study the dynamics of their mutual quantum
correlations in the thermodynamic, large-$N$ limit. We show that dissipation
and noise due to the presence of the external environment are able to generate
collective quantum correlations between the two chains at the mesoscopic level.
The created collective quantum entanglement between the two many-body systems

We study the existence of the maximal quantum Fisher information matrix in
multi-parameter quantum estimation, which bounds the ultimate precision limit.
We show that when the maximal quantum Fisher information matrix exists, it can
be directly obtained from the underlying dynamics. Examples are then provided
to demonstrate the usefulness of the maximal quantum Fisher information matrix
by deriving various tradeoff relations in multi-parameter quantum estimation
and obtaining the bounds for the scalings of the precision limit.