697 research outputs found
Cooling of a micro-mechanical oscillator using radiation pressure induced dynamical back-action
Cooling of a 58 MHz micro-mechanical resonator from room temperature to 11 K
is demonstrated using cavity enhanced radiation pressure. Detuned pumping of an
optical resonance allows enhancement of the blue shifted motional sideband
(caused by the oscillator's Brownian motion) with respect to the red-shifted
sideband leading to cooling of the mechanical oscillator mode. The reported
cooling mechanism is a manifestation of the effect of radiation pressure
induced dynamical backaction. These results constitute an important step
towards achieving ground state cooling of a mechanical oscillator.Comment: accepted for publication (Phys. Rev. Lett.
Persistent Rabi oscillations probed via low-frequency noise correlation
The qubit Rabi oscillations are known to be non-decaying (though with a
fluctuating phase) if the qubit is continuously monitored in the weak-coupling
regime. In this paper we propose an experiment to demonstrate these persistent
Rabi oscillations via low-frequency noise correlation. The idea is to measure a
qubit by two detectors, biased stroboscopically at the Rabi frequency. The
low-frequency noise depends on the relative phase between the two combs of
biasing pulses, with a strong increase of telegraph noise in both detectors for
the in-phase or anti-phase combs. This happens because of self-synchronization
between the persistent Rabi oscillations and measurement pulses. Almost perfect
correlation of the noise in the two detectors for the in-phase regime and
almost perfect anticorrelation for the anti-phase regime indicates a presence
of synchronized persistent Rabi oscillations. The experiment can be realized
with semiconductor or superconductor qubits.Comment: 5 page
Superconducting re-entrant cavity transducer for a resonant bar gravitational radiation antenna
Copyright @ American Institute of PhysicsA 10‐GHz superconducting niobium re‐entrant cavity parametric transducer was developed for use in a cryogenic 1.5‐tonne Nb resonant bar gravitational radiation antenna. The transducer has a very high electrical Q (6×105 at 4.2 K), and was operated at high cavity fields without degrading the Q. A very high electromechanical coupling between the antenna and the transducer was therefore achieved. The highest coupling attained, constrained by the available pump power, was 0.11. If the transducer were to be operated in conjunction with a wideband impedance matching element, an antenna bandwidth comparable to the frequency of the antenna would be attained. The temperature dependence of the Q of the transducer was in good agreement with theory. At temperatures above about 6 K the Q was degraded by the increase in the BCS surface resistance, while at lower temperatures the Q was limited by radiative losses
Entanglement of macroscopic test masses and the Standard Quantum Limit in laser interferometry
We show that the generation of entanglement of two heavily macroscopic
mirrors with masses of up to several kilograms are feasible with state of the
art techniques of high-precision laser interferometry. The basis of such a
demonstration would be a Michelson interferometer with suspended mirrors and
simultaneous homodyne detections at both interferometer output ports. We
present the connection between the generation of entanglement and the Standard
Quantum Limit (SQL) for a free mass. The SQL is a well-known reference limit in
operating interferometers for gravitational-wave detection and provides a
measure of when macroscopic entanglement can be observed in the presence of
realistic decoherence processes
New Photodetection Method Using Unbalanced Sidebands for Squeezed Quantum Noise in Gravitational Wave Interferometer
Homodyne detection is one of the ways to circumvent the standard quantum
limit for a gravitational wave detector. In this paper it will be shown that
the same quantum-non-demolition effect using homodyne detection can be realized
by heterodyne detection with unbalanced RF sidebands. Furthermore, a broadband
quantum-non-demolition readout scheme can also be realized by the unbalanced
sideband detection.Comment: 9 pages, 5 figure
Theory of ground state cooling of a mechanical oscillator using dynamical back-action
A quantum theory of cooling of a mechanical oscillator by radiation
pressure-induced dynamical back-action is developed, which is analogous to
sideband cooling of trapped ions. We find that final occupancies well below
unity can be attained when the mechanical oscillation frequency is larger than
the cavity linewidth. It is shown that the final average occupancy can be
retrieved directly from the optical output spectrum.Comment: 5 pages, 2 figure
Geometric factors in the Bohr--Rosenfeld analysis of the measurability of the electromagnetic field
The Geometric factors in the field commutators and spring constants of the
measurement devices in the famous analysis of the measurability of the
electromagnetic field by Bohr and Rosenfeld are calculated using a
Fourier--Bessel method for the evaluation of folding integrals, which enables
one to obtain the general geometric factors as a Fourier--Bessel series. When
the space region over which the factors are defined are spherical, the
Fourier--Bessel series terms are given by elementary functions, and using the
standard Fourier-integral method of calculating folding integrals, the
geometric factors can be evaluated in terms of manageable closed-form
expressions.Comment: 21 pages, REVTe
Properties of a monolithic sapphire parametric transducer: prospects of measuring the standard quantum limit
To measure the standard quantum limit (SQL) a high quality transducer must be
coupled to a high quality mechanical system. Due to its monolithic nature, the
monolithic sapphire transducer (MST) has high quality factors for both types of
resonances. Single loop suspension is shown to yield a mechanical quality
factor of 6.10^8 at 4 K. From standard analysis we show the MST has the
potential to measure noise fluctuations of the mechanical oscillator at the
SQL. also, we point out a new way to determine if the transducer back action is
quantum limited. We show that if the fluctuations are at the quantum limit,
then the amplitude of the oscillation will be amplified by the ratio of the
ringdown time to the measurement time, which is an inherently easier
measurement.Comment: One PD
Cavity spin optodynamics
The dynamics of a large quantum spin coupled parametrically to an optical
resonator is treated in analogy with the motion of a cantilever in cavity
optomechanics. New spin optodynamic phenonmena are predicted, such as
cavity-spin bistability, optodynamic spin-precession frequency shifts, coherent
amplification and damping of spin, and the spin optodynamic squeezing of light.Comment: 4 pages, 3 figure
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