115,723 research outputs found
High-Order Adiabatic Approximation for Non-Hermitian Quantum System and Complexization of Berry's Phase
In this paper the evolution of a quantum system drived by a non-Hermitian
Hamiltonian depending on slowly-changing parameters is studied by building an
universal high-order adiabatic approximation(HOAA) method with Berry's phase
,which is valid for either the Hermitian or the non-Hermitian cases. This
method can be regarded as a non-trivial generalization of the HOAA method for
closed quantum system presented by this author before. In a general situation,
the probabilities of adiabatic decay and non-adiabatic transitions are
explicitly obtained for the evolution of the non-Hermitian quantum system. It
is also shown that the non-Hermitian analog of the Berry's phase factor for the
non-Hermitian case just enjoys the holonomy structure of the dual linear bundle
over the parameter manifold. The non-Hermitian evolution of the generalized
forced harmonic oscillator is discussed as an illustrative examples.Comment: ITP.SB-93-22,17 page
Quantum-Classical Transition of Photon-Carnot Engine Induced by Quantum Decoherence
We study the physical implementation of the Photon Carnot engine (PCE) based
on the cavity QED system [M. Scully et al, Science, \textbf{299}, 862 (2003)].
Here, we analyze two decoherence mechanisms for the more practical systems of
PCE, the dissipation of photon field and the pure dephasing of the input atoms.
As a result we find that (I) the PCE can work well to some extent even in the
existence of the cavity loss (photon dissipation); and (II) the short-time
atomic dephasing, which can destroy the PCE, is a fatal problem to be overcome.Comment: 6 pages, 3 figure
Quantum Dynamical Model for Wave Function Reduction in Classical and Macroscopic Limits
In this papper, a quantum dynamical model describing the quantum measurement
process is presented as an extensive generalization of the Coleman-Hepp model.
In both the classical limit with very large quantum number and macroscopic
limit with very large particle number in measuring instrument, this model
generally realizes the wave packet collapse in quantum measurement as a
consequence of the Schrodinger time evolution in either the exactly-solvable
case or the non-(exactly-)solvable case.
For the latter, its quasi-adiabatic case is explicitly analysed by making use
of the high-order adiabatic approximation method and then manifests the wave
packet collapse as well as the exactly-solvable case. By highlighting these
analysis, it is finally found that an essence of the dynamical model of wave
packet collapse is the factorization of the Schrodinger evolution other than
the exact solvability. So many dynamical models including the well-known ones
before, which are exactly-solvable or not, can be shown only to be the concrete
realizations of this factorizabilityComment: ITP.SB-93-14,19 page
Cooling of Nanomechanical Resonator Based on Periodical Coupling to Cooper Pair Box
We propose and study an active cooling mechanism for the nanomechanical
resonator (NAMR) based on periodical coupling to a Cooper pair box (CPB), which
is implemented by a designed series of magnetic flux pluses threading through
the CPB. When the initial phonon number of the NAMR is not too large, this
cooling protocol is efficient in decreasing the phonon number by two to three
orders of magnitude. Our proposal is theoretically universal in cooling various
boson systems of single mode. It can be specifically generalized to prepare the
nonclassical state of the NAMR.Comment: 5pages,3figure
The overmassive black hole in NGC 1277: new constraints from molecular gas kinematics
We report the detection of CO(1-0) emission from NGC 1277, a lenticular
galaxy in the Perseus Cluster. NGC 1277 has previously been proposed to host an
overmassive black hole (BH) compared to the galaxy bulge luminosity (mass),
based on stellar-kinematic measurements. The CO(1-0) emission, observed with
the IRAM Plateau de Bure Interferometer (PdBI) using both, a more compact
(2.9-arcsec resolution) and a more extended (1-arcsec resolution)
configuration, is likely to originate from the dust lane encompassing the
galaxy nucleus at a distance of 0.9 arcsec (~320 pc). The double-horned CO(1-0)
profile found at 2.9-arcsec resolution traces of
molecular gas, likely orbiting in the dust lane at $\sim 550\ \mathrm{km\
s^{-1}}\sim 2\times 10^{10}\
M_\odot\sim
1.7\times 10^{10}\ M_\odotM/L_V=6.3\sim 5\times 10^{9}\ M_\odotM/L_V=10$. While the molecular gas reservoir
may be associated with a low level of star formation activity, the extended
2.6-mm continuum emission is likely to originate from a weak AGN, possibly
characterized by an inverted radio-to-millimetre spectral energy distribution.
Literature radio and X-ray data indicate that the BH in NGC 1277 is also
overmassive with respect to the Fundamental Plane of BH activity.Comment: 15 pages, 13 figures; accepted for publication in MNRAS on 20 January
2016; updated version including minor changes and note added in proo
Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSbTe
Substitution of Sb in FeSb by less than 0.5% of Te induces a transition
from a correlated semiconductor to an unconventional metal with large effective
charge carrier mass . Spanning the entire range of the semiconductor-metal
crossover, we observed an almost constant enhancement of the measured
thermopower compared to that estimated by the classical theory of electron
diffusion. Using the latter for a quantitative description one has to employ an
enhancement factor of 10-30. Our observations point to the importance of
electron-electron correlations in the thermal transport of FeSb, and
suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett.
(2011
An quantum approach of measurement based on the Zurek's triple model
In a close form without referring the time-dependent Hamiltonian to the total
system, a consistent approach for quantum measurement is proposed based on
Zurek's triple model of quantum decoherence [W.Zurek, Phys. Rev. D 24, 1516
(1981)]. An exactly-solvable model based on the intracavity system is dealt
with in details to demonstrate the central idea in our approach: by peeling off
one collective variable of the measuring apparatus from its many degrees of
freedom, as the pointer of the apparatus, the collective variable de-couples
with the internal environment formed by the effective internal variables, but
still interacts with the measured system to form a triple entanglement among
the measured system, the pointer and the internal environment. As another
mechanism to cause decoherence, the uncertainty of relative phase and its
many-particle amplification can be summed up to an ideal entanglement or an
Shmidt decomposition with respect to the preferred basis.Comment: 22pages,3figure
Disentanglement in a quantum critical environment
We study the dynamical process of disentanglement of two qubits and two
qutrits coupled to an Ising spin chain in a transverse field, which exhibits a
quantum phase transition. We use the concurrence and negativity to quantify
entanglement of two qubits and two qutrits, respectively. Explicit connections
between the concurrence (negativity) and the decoherence factors are given for
two initial states, the pure maximally entangled state and the mixed Werner
state. We find that the concurrence and negativity decay exponentially with
fourth power of time in the vicinity of critical point of the environmental
system.Comment: 8 pages, 6 figure
- …