Probing macroscopic quantum state with a sub-Heisenberg accuracy

Document #:

LIGO-P0900063-v1

Document type:

P - Publications

Abstract:

Significant achievements in the reduction of classical-noise floor will allow macroscopic systems to prepare nearly Heisenberg-Limited quantum states through a continuous measurement, i.e. conditioning. In order to probe the conditional quantum state and confirm quantum dynamics, we propose use of an optimal time-domain variational measurement, in which the homodyne detection phase varies in time. This protocol allows us to characterize the macroscopic quantum state below the Heisenberg Uncertainty -- i.e. Quantum Tomography -- and the only limitation comes from readout loss which enters in a similar manner as the frequency-domain variational scheme proposed by Kimble et al.. In the case of no readout loss, it is identical to the back-action-evading scheme invented by Vyatchanin et al. for detecting gravitational-wave (GW) signal with known arrival time. As a special example and to motivate Macroscopic Quantum Mechanics (MQM) experiments with future GW detectors, we mostly focus on the free-mass limit -- the characteristic measurement frequency is much higher than the oscillator frequency -- and further assume the classical noises are Markovian, which captures the main feature of a broadband GW detector. Besides, we consider verifications of Einstein-Podolsky-Rosen (EPR) type entanglements between macroscopic test masses in GW detectors, which enables to test one particular version of Gravity Decoherence conjectured by Diosi and Penrose.

Files in Document:

• P0900063_v1.pdf (1.0 MB)

Topics:

• Detector

Authors:

• Henning Rehbein
• Stefan Danilishin
• Kentaro Somiya
• Haixing Miao
• Helge Muller-Ebhardt
• Yanbei Chen

Publication Information:

http://arxiv.org/abs/0905.3729