8,307 research outputs found
Transparency and amplification in a hybrid system of mechanical resonator and circuit QED
We theoretically study the transparency and amplification of a weak probe
field applied to the cavity in hy- brid systems formed by a driven
superconducting circuit QED system and a mechanical resonator, or a driven
optomechanical system and a superconducting qubit. We find that both the
mechanical resonator and the su- perconducting qubit can result in the
transparency to a weak probe field in such hybrid systems when a strong driving
field is applied to the cavity. We also find that the weak probe field can be
amplified in some parameter regimes. We further study the statistical
properties of the output field via the degrees of second-order coherence. We
find that the nonclassicality of the output field strongly depends on the
system parameters. Our studies show that one can control single-photon
transmission in the optomechanical system via a tunable artificial atom or in
the circuit QED system via a mechanical resonator.Comment: 9 pages, 9 figure
Engineering of nonclassical motional states in optomechanical systems
We propose to synthesize arbitrary nonclassical motional states in
optomechanical systems by using sideband excitations and photon blockade. We
first demonstrate that the Hamiltonian of the optomechanical systems can be
reduced, in the strong single-photon optomechanical coupling regime when the
photon blockade occurs, to one describing the interaction between a driven
two-level trapped ion and the vibrating modes, and then show a method to
generate target states by using a series of classical pulses with desired
frequencies, phases, and durations. We further analyze the effect of the photon
leakage, due to small anharmonicity, on the fidelity of the expected motional
state, and study environment induced decoherence. Moreover, we also discuss the
experimental feasibility and provide operational parameters using the possible
experimental data.Comment: 11 pages, 4 figure
All-optical transistor based on Rydberg atom-assisted opto-mechanical system
We study the optical response of double optomechanical cavity system assisted
by Rydberg atomic ensembles. And atomic ensembles are only coupled with one
side cavity by a single cavity mode. It has been realized that a long-range
manipulation for optical properties of hybrid system, by controlling the
Rydberg atomic ensembles decoupled with the optomechanical cavity. Switching on
the coupling between atoms and cavity mode, the original time reversal symmetry
of double cavity structure has been broken. Based on the controlled optical
non-reciprocity, we put forward the theoretical schemes of all-optical
controlled diode, rectifier and transistor
Active User Detection of Uplink Grant-Free SCMA in Frequency Selective Channel
Massive machine type communication (mMTC) is one of the three fifth
generation mobile networking (5G) key usage scenarios, which is characterized
by a very large number of connected devices typically transmitting a relatively
low volume of non-delay sensitive data. To support the mMTC communication, an
uplink (UL) grant-free sparse code multiple access (SCMA) system has been
proposed. In this system, the knowledge of user equipments' (UEs') status
should be obtained before decoding the data by a message passing algorithm
(MPA). An existing solution is to use the compressive sensing (CS) theory to
detect active UEs under the assumed condition of flat fading channel. But the
assumed condition is not suitable for the frequency selective channel and will
decrease the accuracy of active UEs detection. This paper proposes a new simple
module named refined active UE detector (RAUD), which is based on frequency
selective channel gain analyzing. By making full use of the channel gain and
analyzing the difference between characteristic values of the two status of
UEs, RAUD module can enhance the active UEs detection accuracy. Meanwhile, the
addition of the proposed module has a negligible effect on the complexity of UL
grant-free SCMA receiver
Fermion-fermion interaction driven instability and criticality of quadratic band crossing systems with the breaking of time-reversal symmetry
We carefully study how the fermion-fermion interactions affect the low-energy
states of a two-dimensional spin- fermionic system on the kagom\'{e}
lattice with a quadratic band crossing point. With the help of the
renormalization group approach, we can treat all kinds of fermionic
interactions on the the same footing and then establish the coupled
energy-dependent flows of fermionic interaction parameters via collecting
one-loop corrections, from which a number of interesting results are extracted
in the low-energy regime. At first, various sorts of fermion-fermion
interactions furiously compete with each other and are inevitably attracted by
certain fixed point in the parameter space, which clusters into three
qualitatively distinct regions relying heavily upon the structure parameters of
materials. In addition, we notice that an instability accompanied by some
symmetry breaking is triggered around different sorts of fixed points.
Computing and comparing susceptibilities of twelve potential candidates
indicates that charge density wave always dominates over all other
instabilities. Incidently, there exist several subleading ones including the
-current, bond density, and chiral plus s-wave superconductors. Finally, we
realize that strong fluctuations nearby the leading instability prefer to
suppress density of states and specific heat as well compressibility of
quasiparticles in the lowest-energy limit.Comment: 22 pages, 12 figures; Nulcear Physics B 966, 115371 (2021
Statistical Methods and Computing for Big Data
Big data are data on a massive scale in terms of volume, intensity, and
complexity that exceed the capacity of standard software tools. They present
opportunities as well as challenges to statisticians. The role of computational
statisticians in scientific discovery from big data analyses has been
under-recognized even by peer statisticians. This article reviews recent
methodological and software developments in statistics that address the big
data challenges. Methodologies are grouped into three classes:
subsampling-based, divide and conquer, and sequential updating for stream data.
Software review focuses on the open source R and R packages, covering recent
tools that help break the barriers of computer memory and computing power. Some
of the tools are illustrated in a case study with a logistic regression for the
chance of airline delay
Volatility swaps valuation under stochastic volatility with jumps and stochastic intensity
In this paper, a pricing formula for volatility swaps is delivered when the
underlying asset follows the stochastic volatility model with jumps and
stochastic intensity. By using Feynman-Kac theorem, a partial integral
differential equation is obtained to derive the joint moment generating
function of the previous model.
Moreover, discrete and continuous sampled volatility swap pricing formulas
are given by employing transform techniques and the relationship between two
pricing formulas is discussed. Finally, some numerical simulations are reported
to support the results presented in this paper.Comment: 15PAGE
Ice-Flower Systems And Star-graphic Lattices
Lattice theory has been believed to resist classical computers and quantum
computers. Since there are connections between traditional lattices and graphic
lattices, it is meaningful to research graphic lattices. We define the
so-called ice-flower systems by our uncolored or colored leaf-splitting and
leaf-coinciding operations. These ice-flower systems enable us to construct
several star-graphic lattices. We use our star-graphic lattices to express some
well-known results of graph theory and compute the number of elements of a
particular star-graphic lattice. For more researching ice-flower systems and
star-graphic lattices we propose Decomposition Number String Problem, finding
strongly colored uniform ice-flower systems and connecting our star-graphic
lattices with traditional lattices
Phonon amplification in two coupled cavities containing one mechanical resonator
We study a general theory of phonon lasing [I. S. Grudinin et al., Phys. Rev.
Lett. 104, 083901 (2010)] in coupled optomechancial systems. We derive the
dynamical equation of the phonon lasing using supermodes formed by two cavity
modes. A general threshold condition for phonon lasing is obtained. We also
show the differences between phonon lasing and photon lasing, generated by
photonic supermodes and two-level atomic systems, respectively. We find that
the phonon lasing can be realized in certain parameter regime near the
threshold. The phase diagram and second-order correlation function of the
phonon lasing are also studied to show some interesting phenomena that cannot
be observed in the common photon lasing with the two-level systems.Comment: 11 pages, 8 figure
Creation of a new vector field and focusing engineering
Recently many methods have been proposed to create the vector fields, due to
the academic interest and a variety of attractive applications such as for
particle acceleration, optical trapping, particle manipulation, and
fluorescence imaging. For the most of the created vector fields, the spatial
distribution in states of polarization (SoPs) is dependent of azimuthal angle
only. It is very interesting and crucial that if we can introduce the radial
controlling freedom, which undoubtedly opens a new way to provide the
flexibility for creating the desired vector fields and for fulfilling the
requirement on a variety of applications. Here we present a new idea to create
a new kind of vector filed with the radial-variant SoPs. This idea also permits
to create flexibly vector fields with arbitrarily complex distribution of SoPs,
based on a combination of radial and azimuthal dependency. This realization in
both principle and experiment is paramount to be able to implement the focusing
engineering for applications in a variety of realms. Specially arranging the
SoPs of vector fields, purposefully and carefully, is anticipated to lead to
new effects and phenomena that can expand the functionality and enhance the
capability of optical systems, such as the optical trapping.Comment: 13 pages, 8 figure
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