1,261 research outputs found
Transport and bistable kinetics of a Brownian particle in a nonequilibrium environment
A system reservoir model, where the associated reservoir is modulated by an
external colored random force, is proposed to study the transport of an
overdamped Brownian particle in a periodic potential. We then derive the
analytical expression for the average velocity, mobility, and diffusion rate.
The bistable kinetics and escape rate from a metastable state in the overdamped
region are studied consequently. By numerical simulation we then demonstrate
that our analytical escape rate is in good agreement with that of numerical
result.Comment: 10 pages, 2 figures, RevTex4, minor correction
Excitability in semiconductor microring lasers: Experimental and theoretical pulse characterization
We characterize the operation of semiconductor microring lasers in an
excitable regime. Our experiments reveal a statistical distribution of the
characteristics of noise-triggered optical pulses that is not observed in other
excitable systems. In particular, an inverse correlation exists between the
pulse amplitude and duration. Numerical simulations and an interpretation in an
asymptotic phase space confirm and explain these experimentally observed pulse
characteristics.Comment: 9 pages, 10 figure
Dissipative solitons in pattern-forming nonlinear optical systems : cavity solitons and feedback solitons
Many dissipative optical systems support patterns. Dissipative solitons are generally found where a pattern coexists with a stable unpatterned state. We consider such phenomena in driven optical cavities containing a nonlinear medium (cavity solitons) and rather similar phenomena (feedback solitons) where a driven nonlinear optical medium is in front of a single feedback mirror. The history, theory, experimental status, and potential application of such solitons is reviewed
Remnants of semiclassical bistability in the few-photon regime of cavity QED
Broadband homodyne detection of the light transmitted by a Fabry-Perot cavity
containing a strongly-coupled Cs atom is used to probe the dynamic
optical response in a regime where semiclassical theory predicts bistability
but strong quantum corrections should apply. While quantum fluctuations
destabilize true equilibrium bistability, our observations confirm the
existence of metastable states with finite lifetimes and a hysteretic response
is apparent when the optical drive is modulated on comparable timescales. Our
experiment elucidates remnant semiclassical behavior in the attojoule (
photon) regime of single-atom cavity QED, of potential significance for
ultra-low power photonic signal processing.Comment: 14 pages, 7 figure
Engineering Gaussian states of light from a planar microcavity
Quantum fluids of light in a nonlinear planar microcavity can exhibit
antibunched photon statistics at short distances due to repulsive polariton
interactions. We show that, despite the weakness of the nonlinearity, the
antibunching signal can be amplified orders of magnitude with an appropriate
free-space optics scheme to select and interfere output modes. Our results are
understood from the unconventional photon blockade perspective by analyzing the
approximate Gaussian output state of the microcavity. In a second part, we
illustrate how the temporal and spatial profile of the density-density
correlation function of a fluid of light can be reconstructed with free-space
optics. Also here the nontrivial (anti)bunching signal can be amplified
significantly by shaping the light emitted by the microcavity
Nonlinear relaxation phenomena in metastable condensed matter systems
Nonlinear relaxation phenomena in three different systems of condensed matter are investigated. (i) First, the phase dynamics in Josephson junctions is analyzed. Specifically, a superconductor-graphene-superconductor (SGS) system exhibits quantum metastable states, and the average escape time from these metastable states in the presence of Gaussian and correlated fluctuations is calculated, accounting for variations in the the noise source intensity and the bias frequency. Moreover, the transient dynamics of a long-overlap Josephson junction (JJ) subject to thermal fluctuations and non-Gaussian noise sources is investigated. Noise induced phenomena are observed, such as the noise enhanced stability and the stochastic resonant activation. (ii) Second, the electron spin relaxation process in a n-type GaAs bulk driven by a fluctuating electric field is investigated. In particular, by using a Monte Carlo approach, we study the influence of a random telegraph noise on the spin polarized transport. Our findings show the possibility to raise the spin relaxation length by increasing the amplitude of the external fluctuations. Moreover, we find that, crucially, depending on the value of the external field strength, the electron spin depolarization length versus the noise correlation time increases up to a plateau. (iii) Finally, the stabilization of quantum metastable states by dissipation is presented. Normally, quantum fluctuations enhance the escape from metastable states in the presence of dissipation. We show that dissipation can enhance the stability of a quantum metastable system, consisting of a particle moving in a strongly asymmetric double well potential, interacting with a thermal bath. We find that the escape time from the metastable region has a nonmonotonic behavior versus the system- bath coupling and the temperature, producing a stabilizing effect
Stochastic resonance in electrical circuits—II: Nonconventional stochastic resonance.
Stochastic resonance (SR), in which a periodic signal in a nonlinear system can be amplified by added noise, is discussed. The application of circuit modeling techniques to the conventional form of SR, which occurs in static bistable potentials, was considered in a companion paper. Here, the investigation of nonconventional forms of SR in part using similar electronic techniques is described. In the small-signal limit, the results are well described in terms of linear response theory. Some other phenomena of topical interest, closely related to SR, are also treate
Spin-Cooling of the Motion of a Trapped Diamond
Observing and controlling macroscopic quantum systems has long been a driving
force in research on quantum physics. In this endeavor, strong coupling between
individual quantum systems and mechanical oscillators is being actively
pursued. While both read-out of mechanical motion using coherent control of
spin systems and single spin read-out using pristine oscillators have been
demonstrated, temperature control of the motion of a macroscopic object using
long-lived electronic spins has not been reported. Here, we observe both a
spin-dependent torque and spin-cooling of the motion of a trapped microdiamond.
Using a combination of microwave and laser excitation enables the spin of
nitrogen-vacancy centers to act on the diamond orientation and to cool the
diamond libration via a dynamical back-action. Further, driving the system in
the non-linear regime, we demonstrate bistability and self-sustained coherent
oscillations stimulated by the spin-mechanical coupling, which offers prospects
for spin-driven generation of non-classical states of motion. Such a levitating
diamond operated as a compass with controlled dissipation has implications in
high-precision torque sensing, emulation of the spin-boson problem and probing
of quantum phase transitions. In the single spin limit and employing ultra-pure
nano-diamonds, it will allow quantum non-demolition read-out of the spin of
nitrogen-vacancy centers under ambient conditions, deterministic entanglement
between distant individual spins and matter-wave interferometry.Comment: New version with a calibration of angular resolution and sensitivity.
Fig. 1 is also replaced to show an ODMR when the diamond is static to avoid
spin-torque induced distortion
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