3,061 research outputs found
Trigonometric protocols for shortcuts to adiabatic transport of cold atoms in anharmonic traps
Shortcuts to adiabaticity have been proposed to speed up the "slow" adiabatic
transport of an atom or a wave packet of atoms. However, the freedom of the
inverse engineering approach with appropriate boundary conditions provides
thousands of trap trajectories for different purposes, for example, time and
energy minimizations. In this paper, we propose trigonometric protocols for
fast and robust atomic transport, taking into account cubic or quartic
anharmonicities. The numerical results have illustrated that such trigonometric
protocols, particular cosine ansatz, is more robust and the corresponding final
energy excitation is smaller, as compared to sine trajectories implemented in
previous experiments.Comment: 5 pages, 5 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
Filtered-OFDM - Enabler for Flexible Waveform in The 5th Generation Cellular Networks
The underlying waveform has always been a shaping factor for each generation
of the cellular networks, such as orthogonal frequency division multiplexing
(OFDM) for the 4th generation cellular networks (4G). To meet the diversified
and pronounced expectations upon the upcoming 5G cellular networks, here we
present an enabler for flexible waveform configuration, named as filtered-OFDM
(f-OFDM). With the conventional OFDM, a unified numerology is applied across
the bandwidth provided, balancing among the channel characteristics and the
service requirements, and the spectrum efficiency is limited by the compromise
we made. In contrast, with f-OFDM, the assigned bandwidth is split up into
several subbands, and different types of services are accommodated in different
subbands with the most suitable waveform and numerology, leading to an improved
spectrum utilization. After outlining the general framework of f-OFDM, several
important design aspects are also discussed, including filter design and guard
tone arrangement. In addition, an extensive comparison among the existing 5G
waveform candidates is also included to illustrate the advantages of f-OFDM.
Our simulations indicate that, in a specific scenario with four distinct types
of services, f-OFDM provides up to 46% of throughput gains over the
conventional OFDM scheme.Comment: Accepted to IEEE Globecom, San Diego, CA, Dec. 201
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
Spinor wave equation of photon
In this paper, we give the spinor wave equations of free and unfree photon,
which are the differential equation of space-time one order. For the free
photon, the spinor wave equations are covariant, and the spinors are
corresponding to the the reducibility representations and
of the proper Lorentz group
Coherent-feedback-induced photon blockade and optical bistability by an optomechanical controller
It is well-known that some nonlinear phenomena such as strong photon blockade
are hard to be observed in optomechanical system with current experimental
technology. Here, we present a coherent feedback control strategy in which a
linear cavity is coherently controlled by an optomechanical controller in a
feedback manner. The coherent feedback loop transfers and enhances quantum
nonlinearity from the controller to the controlled cavity, which makes it
possible to observe strong nonlinear effects in either linear cavity or
optomechanical cavity. More interestingly, we find that the strong photon
blockade under single-photon optomechanical weak coupling condition could be
observed in the quantum regime. Additionally, the coherent feedback loop leads
to two-photon and multiphoton tunnelings for the controlled linear cavity,
which are also typical quantum nonlinear phenomenon. We hope that our work can
give new perspectives in engineering nonlinear quantum phenomena.Comment: 12 pages, 11 figure
Tunable Flux through a Synthetic Hall Tube of Neutral Fermions
Hall tube with a tunable flux is an important geometry for studying quantum
Hall physics, but its experimental realization in real space is still
challenging. Here, we propose to realize a synthetic Hall tube with tunable
flux in a one-dimensional optical lattice with the synthetic ring dimension
defined by atomic hyperfine states. We investigate the effects of the flux on
the system topology and study its quench dynamics. Utilizing the tunable flux,
we show how to realize topological charge pumping, where interesting charge
flow and transport are observed in rotated spin basis. Finally, we show that
the recently observed quench dynamics in a synthetic Hall tube can be explained
by the random flux existing in the experiment.Comment: 6 pages, 7 figure
Quantum feedback: theory, experiments, and applications
The control of individual quantum systems is now a reality in a variety of
physical settings. Feedback control is an important class of control methods
because of its ability to reduce the effects of noise. In this review we give
an introductory overview of the various ways in which feedback may be
implemented in quantum systems, the theoretical methods that are currently used
to treat it, the experiments in which it has been demonstrated to-date, and its
applications. In the last few years there has been rapid experimental progress
in the ability to realize quantum measurement and control of mesoscopic
systems. We expect that the next few years will see further rapid advances in
the precision and sophistication of feedback control protocols realized in the
laboratory.Comment: Updated version of a review paper about quantum feedbac
Entanglement distribution over quantum code-division-multiple-access networks
We present a method for quantum entanglement distribution over a so-called
code-division-multiple-access network, in which two pairs of users share the
same quantum channel to transmit information. The main idea of this method is
to use different broad-band chaotic phase shifts, generated by electro-optic
modulators (EOMs) and chaotic Colpitts circuits, to encode the
information-bearing quantum signals coming from different users, and then
recover the masked quantum signals at the receiver side by imposing opposite
chaotic phase shifts. The chaotic phase shifts given to different pairs of
users are almost uncorrelated due to the randomness of chaos and thus the
quantum signals from different pair of users can be distinguished even when
they are sent via the same quantum channel. It is shown that two
maximally-entangled states can be generated between two pairs of users by our
method mediated by bright coherent lights, which can be more easily implemented
in experiments compared with single-photon lights. Our method is robust under
the channel noises if only the decay rates of the information-bearing fields
induced by the channel noises are not quite high. Our study opens up new
perspectives for addressing and transmitting quantum information in future
quantum networks
Quantum Coherent Nonlinear Feedbacks with Applications to Quantum Optics on Chip
In the control of classical mechanical systems, the feedback has been
successfully applied to the production of the desired nonlinear dynamics.
However, how much this can be done is still an open problem in quantum
mechanical systems. This paper proposes a scheme of generating strong nonlinear
quantum effects via the recently developed coherent feedback techniques, which
can be shown to outperform the measurement-based quantum feedback scheme that
can only generate pseudo-nonlinear quantum effects. Such advancement is
demonstrated by two application examples in quantum optics on chip. In the
first example, we show that the nonlinear Kerr effect can be generated and
amplified to be comparable with the linear effect in a transmission line
resonator (TLR). In the second example, we show that by tuning the gains of the
quantum amplifiers in a TLR coherent feedback network, non-Gaussian "light"
(microwave field) can be generated and manipulated via the nonlinear effects
which exhibits fully quantum sub-Poisson photoncount statistics and photon
antibunching phenomenon. The scheme opens promising applications in
demonstrating strong nonlinear quantum optics on chip, which is extremely weak
and inflexible in traditional quantum optical devices.Comment: 12 pages, 9 figure
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