4,715 research outputs found
Physical Limits of Heat-Bath Algorithmic Cooling
Simultaneous near-certain preparation of qubits (quantum bits) in their ground states is a key hurdle in quantum computing proposals as varied as liquid-state NMR and ion traps. “Closed-system” cooling mechanisms are of limited applicability due to the need for a continual supply of ancillas for fault tolerance and to the high initial temperatures of some systems. “Open-system” mechanisms are therefore required. We describe a new, efficient initialization procedure for such open systems. With this procedure, an -qubit device that is originally maximally mixed, but is in contact with a heat bath of bias , can be almost perfectly initialized. This performance is optimal due to a newly discovered threshold effect: For bias no cooling procedure can, even in principle (running indefinitely without any decoherence), significantly initialize even a single qubit
Dynamical thermal behavior and thermal self-stability of microcavities
As stability and continuous operation are important for almost any use of a microcavity, we demonstrate here experimentally and theoretically a self-stable equilibrium solution for a pump-microcavity system. In this stable equilibrium, intensity- and wavelength-perturbations cause a small thermal resonant-drift that is enough to compensate for the perturbation (noises); consequently the cavity stays warm and loaded as perturbations are self compensated. We also compare here, our theoretical prediction for the thermal line broadening (and for the wavelength hysteretic response) to experimental results
Direct imaging of tunneling from a potential well
We experimentally map the wavefunction in the vicinity of a radial potential well. We photograph light intensity near the tunneling region as well as measure the spiraling phase structure via interference with a reference wave. This spiraling phase structure is required for conservation of angular momentum. The experimental image reveals the non-intuitive emission of light from a region in space that is empty of material and relatively far from the device
The orbital statistics of stellar inspiral and relaxation near a massive black hole: characterizing gravitational wave sources
We study the orbital parameters distribution of stars that are scattered into
nearly radial orbits and then spiral into a massive black hole (MBH) due to
dissipation, in particular by emission of gravitational waves (GW). This is
important for GW detection, e.g. by the Laser Interferometer Space Antenna
(LISA). Signal identification requires knowledge of the waveforms, which depend
on the orbital parameters. We use analytical and Monte Carlo methods to analyze
the interplay between GW dissipation and scattering in the presence of a mass
sink during the transition from the initial scattering-dominated phase to the
final dissipation-dominated phase of the inspiral. Our main results are (1)
Stars typically enter the GW-emitting phase with high eccentricities. (2) The
GW event rate per galaxy is a few per Gyr for typical central stellar cusps,
almost independently of the relaxation time or the MBH mass. (3) For
intermediate mass black holes (IBHs) of ~a thousand solar masses such as may
exist in dense stellar clusters, the orbits are very eccentric and the inspiral
is rapid, so the sources are very short-lived.Comment: ApJ Accepte
Chaotic Quivering of Micron-Scaled On-Chip Resonators Excited by Centrifugal Optical Pressure
Opto-mechanical chaotic oscillation of an on-chip resonator is excited by the radiation-pressure nonlinearity. Continuous optical input, with no external feedback or modulation, excites chaotic vibrations in very different geometries of the cavity (both tori and spheres) and shows that opto-mechanical chaotic oscillations are an intrinsic property of optical microcavities. Measured phenomena include period doubling, a spectral continuum, aperiodic oscillations, and complex trajectories. The rate of exponential divergence from a perturbed initial condition (Lyapunov exponent) is calculated. Continuous improvements in cavities mean that such chaotic oscillations can be expected in the future with many other platforms, geometries, and frequency spans
Opto-Mechanical Chaotic Behaviour of Micron-Scaled On-Chip Resonators
Opto-mechanical vibration of an on-chip oscillator is experimentally excited by radiation-pressure nonlinearity to a regime where oscillation is chaotic. Period-doubling and broad power spectra are measured in spherical and toroidal-resonators
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