Quantum engineering of squeezed states for quantum communication and metrology

We report the experimental realization of squeezed quantum states of light, tailored for new applications in quantum communication and metrology. Squeezed states in a broad Fourier frequency band down to 1 Hz has been observed for the first time. Nonclassical properties of light in such a low frequency band is required for high efficiency quantum information storage in electromagnetically induced transparency (EIT) media. The states observed also cover the frequency band of ultra-high precision laser interferometers for gravitational wave detection and can be used to reach the regime of quantum non-demolition interferometry. And furthermore, they cover the frequencies of motions of heavily macroscopic objects and might therefore support the attempts to observe entanglement in our macroscopic world.Comment: 12 pages, 3 figure

Beating quantum limits in interferometers with quantum locking of mirrors

The sensitivity in interferometric measurements such as gravitational-wave detectors is ultimately limited by quantum noise of light. We discuss the use of feedback mechanisms to reduce the quantum effects of radiation pressure. Recent experiments have shown that it is possible to reduce the thermal motion of a mirror by cold damping. The mirror motion is measured with an optomechanical sensor based on a high-finesse cavity, and reduced by a feedback loop. We show that this technique can be extended to lock the mirror at the quantum level. In gravitational-waves interferometers with Fabry-Perot cavities in each arms, it is even possible to use a single feedback mechanism to lock one cavity mirror on the other. This quantum locking greatly improves the sensitivity of the interferometric measurement. It is furthermore insensitive to imperfections such as losses in the interferometer

Optomechanical characterization of acoustic modes in a mirror

We present an experimental study of the internal mechanical vibration modes of a mirror. We determine the frequency repartition of acoustic resonances via a spectral analysis of the Brownian motion of the mirror, and the spatial profile of the acoustic modes by monitoring their mechanical response to a resonant radiation pressure force swept across the mirror surface. We have applied this technique to mirrors with cylindrical and plano-convex geometries, and compared the experimental results to theoretical predictions. We have in particular observed the gaussian modes predicted for plano-convex mirrors.Comment: 8 pages, 8 figures, RevTe

Sensitivity of a cavityless optomechanical system

We study the possibility of revealing a weak coherent force by using a pendular mirror as a probe, and coupling this to a radiation field, which acts as the meter, in a cavityless configuration. We determine the sensitivity of such a scheme and show that the use of an entangled meter state greatly improves the ultimate detection limit. We also compare this scheme with that involving an optical cavity.Comment: 4 pages, RevTex file, 2 eps figures, provisionally accepted by Phys. Rev.

Divergent selection for humoral immune responsiveness in chickens: distribution and effects of major histocompatibility complex types

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Can optical squeezing be generated via polarization self-rotation in a thermal vapour cell?

The traversal of an elliptically polarized optical field through a thermal vapour cell can give rise to a rotation of its polarization axis. This process, known as polarization self-rotation (PSR), has been suggested as a mechanism for producing squeezed light at atomic transition wavelengths. In this paper, we show results of the characterization of PSR in isotopically enhanced Rubidium-87 cells, performed in two independent laboratories. We observed that, contrary to earlier work, the presence of atomic noise in the thermal vapour overwhelms the observation of squeezing. We present a theory that contains atomic noise terms and show that a null result in squeezing is consistent with this theory.Comment: 10 pages, 11 figures, submitted to PRA. Please email author for a PDF file if the article does not appear properl

Noise reduction in gravitational wave interferometers using feedback

We show that the quantum locking scheme recently proposed by Courty {\it et al.} [Phys. Rev. Lett. {\bf 90}, 083601 (2003)] for the reduction of back action noise is able to significantly improve the sensitivity of the next generation of gravitational wave interferometers.Comment: 12 pages, 2 figures, in print in the Special Issue of J. Opt. B on Fluctuations and Noise in Photonics and Quantum Optic

Optomechanical circuits for nanomechanical continuous variable quantum state processing

We propose and analyze a nanomechanical architecture where light is used to perform linear quantum operations on a set of many vibrational modes. Suitable amplitude modulation of a single laser beam is shown to generate squeezing, entanglement, and state-transfer between modes that are selected according to their mechanical oscillation frequency. Current optomechanical devices based on photonic crystals may provide a platform for realizing this scheme.Comment: 11 pages, 5 figure

Radiation-pressure self-cooling of a micromirror in a cryogenic environment

We demonstrate radiation-pressure cavity-cooling of a mechanical mode of a micromirror starting from cryogenic temperatures. To achieve that, a high-finesse Fabry-Perot cavity (F\approx 2200) was actively stabilized inside a continuous-flow 4He cryostat. We observed optical cooling of the fundamental mode of a 50mu x 50 mu x 5.4 mu singly-clamped micromirror at \omega_m=3.5 MHz from 35 K to approx. 290 mK. This corresponds to a thermal occupation factor of \approx 1x10^4. The cooling performance is only limited by the mechanical quality and by the optical finesse of the system. Heating effects, e.g. due to absorption of photons in the micromirror, could not be observed. These results represent a next step towards cavity-cooling a mechanical oscillator into its quantum ground state

Quantum-limited force measurement with an optomechanical device

We study the detection of weak coherent forces by means of an optomechanical device formed by a highly reflecting isolated mirror shined by an intense and highly monochromatic laser field. Radiation pressure excites a vibrational mode of the mirror, inducing sidebands of the incident field, which are then measured by heterodyne detection. We determine the sensitivity of such a scheme and show that the use of an entangled input state of the two sideband modes improves the detection, even in the presence of damping and noise acting on the mechanical mode.Comment: 8 pages, 4 figure