179 research outputs found
Spin-orbit-induced bound state and molecular signature of the degenerate Fermi gas in a narrow Feshbach resonance
In this paper we explore the spin-orbit-induced bound state and molecular
signature of the degenerate Fermi gas in a narrow Feshbach resonance based on a
generalized two-channel model. Without the atom-atom interactions, only one
bound state can be found even if spin-orbit coupling exists. Moreover, the
corresponding bound-state energy depends strongly on the strength of spin-orbit
coupling, but is influenced slightly by its type. In addition, we find that
when increasing the strength of spin-orbit coupling, the critical point at
which the molecular fraction vanishes shifts from zero to the negative
detuning. In the weak spin-orbit coupling, this shifting is proportional to the
square of its strength. Finally, we also show that the molecular fraction can
be well controlled by spin-orbit coupling.Comment: Major modificatio
The Peregrine rogue waves induced by interaction between the continuous wave and soliton
Based on the soliton solution on a continuous wave background for an
integrable Hirota equation, the reduction mechanism and the characteristics of
the Peregrine rogue wave in the propagation of femtosecond pulses of optical
fiber are discussed. The results show that there exist two processes of the
formation of the Peregrine rogue wave: one is the localized process of the
continuous wave background, and the other is the reduction process of the
periodization of the bright soliton. The characteristics of the Peregrine rogue
wave are exhibited by strong temporal and spatial localization. Also, various
initial excitations of the Peregrine rogue wave are performed and the results
show that the Peregrine rogue wave can be excited by a small localized (single
peak) perturbation pulse of the continuous wave background, even for the
nonintegrable case. The numerical simulations show that the Peregrine rogue
wave is unstable. Finally, through a realistic example, the influence of the
self-frequency shift to the dynamics of the Peregrine rogue wave is discussed.
The results show that in the absence of the self-frequency shift, the Peregrine
rogue wave can split into several subpuslses; however, when the self-frequency
shift is considered, the Peregrine rogue wave no longer splits and exhibits
mainly a peak changing and an increasing evolution property of the field
amplitude.Comment: The paper has been accepted by Phys. Rev.
Topological quantum walks in cavity-based quantum networks
We present a protocol to implement discrete-time quantum walks and simulate
topological insulator phases in cavity-based quantum networks, where the single
photon is the quantum walker and the cavity input-output process is employed to
realize the state-dependent translation operation. Different topological phases
can be simulated through tuning the single-photon polarization rotation angles.
We show that both the topological boundary states and topological phase
transitions can be directly observed via measuring the final photonic density
distribution. Moreover, we also demonstrate that these topological signatures
are quite robust to practical imperfections. Our work opens a new prospect
using cavity-based quantum networks as quantum simulators to study
discrete-time quantum walks and mimic condensed matter physics.Comment: 9 pages, 5 figure
Quantum resonant effect of the strongly-driven spin-boson model
In this paper we discuss both analytically and numerically the rich quantum
dynamics of the spin-boson model driven by a time-independent field of photon.
Interestingly, we predict a new Rabi oscillation, whose period is inversely
proportional to the driving amplitude. More surprisingly, some nonzero resonant
peaks are found for some special values of the \emph{strong} driving regime.
Moreover, for the different resonant positions, the peaks have different
values. Thus, an important application of this resonance effect is to realize
the precision measurement of the relative parameters in experiment. We also
illustrate that this resonant effect arises from the interference of the
nontrivial periodic phase factors induced by the evolution of the coherent
states in two different subspaces. Our predictions may be, in principle,
observed in the solid-state cavity quantum electrodynamics with the ultrastrong
coupling if the driving magnitude of the photon field is sufficiently large.Comment: 4 figures; Submitted for publication in Marc
Control of high power pulse extracted from the maximally compressed pulse in a nonlinear optical fiber
We address the possibility to control high power pulses extracted from the
maximally compressed pulse in a nonlinear optical fiber by adjusting the
initial excitation parameters. The numerical results show that the power,
location and splitting order number of the maximally compressed pulse and the
transmission features of high power pulses extracted from the maximally
compressed pulse can be manipulated through adjusting the modulation amplitude,
width, and phase of the initial Gaussian-type perturbation pulse on a
continuous wave background.Comment: 12 pages, 7 figures, The paper has been accepted by Rom. Rep. Phy
Analytical solutions for the Rabi model
The Rabi model that describes the fundamental interaction between a two-level
system with a quantized harmonic oscillator is one of the simplest and most
ubiquitous models in modern physics. However, this model has not been solved
exactly because it is hard to find a second conserved quantity besides the
energy. Here we present a unitary transformation to map this unsolvable Rabi
model into a solvable Jaynes-Cummings-like model by choosing a proper variation
parameter. As a result, the analytical energy spectrums and wavefunctions
including both the ground and the excited states can be obtained easily.
Moreover, these explicit results agree well with the direct numerical
simulations in a wide range of the experimental parameters. In addition, based
on our obtained energy spectrums, the recent experimental observation of
Bloch-Siegert in the circuit quantum electrodynamics with the ultrastrong
coupling can be explained perfectly. Our results have the potential application
in the solid-state quantum information processing.Comment: 5 pages, 4 figure
Enhanced transmission capacity for laser communication at the single-photon level using the multi-channel frequency coding scheme
The statistical properties of a radiation sources are commonly characterized
by second-order-correlation or Mandel parameter. Our research found that the
single photons modulation spectrum provides us another optional way which is
more sensitive to the high frequency information contained in the photon
sequence. In this paper, we present direct laser communication by using a
multi-channel frequency coding scheme based on the single photons modulation
spectrum in which the multi-frequency modulation makes the transmission
capacity efficiently enhanced. The modulation frequencies could be operated in
a wide band without frequency aliasing due to the inherent randomness of
photons arrival time of weak coherent light. The error rate less than 10-5 has
been achieved experimentally when the mean signal photon count is 80 kcps. The
modulated coherent light field shows nonlinear effects of single photons
modulation spectrum. The studies of statistical properties of the single
photons modulation spectrum, including the dependence of mean noise photon
count, integration time, channel spacing and the number of frequency component,
helped us to optimize the error rate and transmission capacity.Comment: There are 11 pages, 9 figures in the paper. In this paper, we
proposed a new MCFC coding scheme, which is specially designed for laser
communication when the received signal is at the single-photon leve
Topology-dependent quantum dynamics and entanglement-dependent topological pumping in superconducting qubit chains
We propose a protocol using a tunable Xmon qubit chain to construct
generalized Su-Schrieffer-Heeger (SSH) models that support various topological
phases. We study the time evolution of a single-excitation quantum state in a
SSH-type qubit chain and find that such dynamics is linked to topological
winding number. We also investigate the adiabatic transfer of a
single-excitation quantum state in a generalized SSH-type qubit chain and show
that this process can be connected with topological Chern number and be used to
generate a novel entanglement-dependent topological pumping. All results have
been demonstrated to be robust against qubit coupling imperfections and can be
observed in a short Xmon qubit chain. Our study provides a simple method to
directly measure topological invariants rooted in momentum space using quantum
dynamics in real space.Comment: 7 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1711.0775
Interaction-induced exotic vortex states in an optical lattice clock with spin-orbit coupling
Motivated by a recent experiment [L. F. Livi, et al., Phys. Rev. Lett. 117,
220401(2016)], we study the ground-state properties of interacting fermions in
a one-dimensional optical lattice clock with spin-orbit coupling. As the
electronic and the hyperfine-spin states in the clock-state manifolds can be
treated as effective sites along distinct synthetic dimensions, the system can
be considered as multiple two-leg ladders with uniform magnetic flux
penetrating the plaquettes of each ladder. As the inter-orbital spin-exchange
interactions in the clock-state manifolds couple individual ladders together,
we show that exotic interaction-induced vortex states emerge in the
coupled-ladder system, which compete with existing phases of decoupled ladders
and lead to a rich phase diagram. Adopting the density matrix renormalization
group approach, we map out the phase diagram, and investigate in detail the
currents and the density-density correlations of the various phases. Our
results reveal the impact of interactions on spin-orbit coupled systems, and
are particularly relevant to the on-going exploration of spin-orbit coupled
optical lattice clocks
Synthetic spin-orbit coupling and topological polaritons in Janeys-Cummings lattices
The interaction between a photon and a qubit in the Janeys-Cummings (JC)
model generates a kind of quasiparticle called polariton. While they are widely
used in quantum optics, difficulties in engineering controllable coupling of
them severely limit their applications to simulate spinful quantum systems.
Here we show that, in the superconducting quantum circuit context, polariton
states in the single-excitation manifold of a JC lattice can be used to
simulate a spin-1/2 system, based on which tunable synthetic spin-orbit
coupling and novel topological polaritons can be generated and explored. The
lattice is formed by a sequence of coupled transmission line resonators, each
of which is connected to a transmon qubit. Synthetic spin-orbit coupling and
effective Zeeman field of the polariton can both be tuned by modulating the
coupling strength between neighbouring resonators, allowing for the realization
of a large variety of polaritonic topological semimetal bands. Methods for
detecting the polaritonic topological edge states and topological invariants
are also proposed. Therefore, our work suggests that the JC lattice is a
versatile platform for exploring spinful topological states of matter, which
may inspire developments of topologically protected quantum optical and
information processing devices.Comment: V2: Extended rewritten version; V3: Accepted version; V4 published
version with correction
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