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What we
do
Since the first squeezing experiment in 1985 by Slusher et al. [1] techniques of generating squeezed light has been improved considerably. Squeezed noise power variances of -7 dB has been demonstrated using optical parametric oscillators (OPO) or amplifiers (OPA). Increasing the squeezing strength is one of the major goals of this project and is tackled together with the Australian National University (P. K. Lam) and the Massachusetts Institute of Technology (N. Mavalvala). A second task is to demonstrate squeezing at lower sideband frequencies. Stable sources of squeezing at low frequencies are of special interest for the gravitational-wave community since it is known that squeezed states injected into a gravitational wave interferometer will increase its sensitivity - even below the standard quantum limit (SQL). Until recently almost all squeezing experiments have been performed in the MHz sideband spectrum. Contrary gravitational wave interferometers (the third generation) will require squeezing between 10 Hz and 10 kHz.
Our goal is the optimization of stable squeezed light generation for applications in gravitational wave astronomy and quantum information. The squeezed light sources investigated build on parametric oscillation, second harmonic generation and the Kerr effect. Our recent experiments demonstrated a new coherent control scheme for squeezed states at audio Fourier frequencies [2, 3]. The first squeezed states at such low frequencies were first demonstrated in [4] and are now available for stable operation in the detection band of gravitational wave detectors.
Our research is supported by the projects B15 and B16 of SFB407 of the Deutsche Forschungsgemeinschaft.
[1] R.E.Slusher, L. W. Hollberg, B. Yurke, J. C. Mertz, and J. F. Valley, Observation of Squeezed States Generated by Four-Wave Mixing in an Optical Cavity, Phys. Rev. Lett. 55, 2409 (1985)
[2] S H. Vahlbruch, S. Chelkowski, B. Hage, A. Franzen, K. Danzmann, and R. Schnabel:
Coherent control of vacuum squeezing in the gravitational-wave detection band,
Phys. Rev. Lett. 97, 011101 (2006)
[3] S. Chelkowski, H. Vahlbruch, K. Danzmann, and R. Schnabel, Coherent control of broadband vacuum squeezing, Phys. Rev. A 75, 043814 (2007)
[4] K. McKenzie, N. Grosse, W. P. Bowen, S. E.Whitcomb, M. B. Gray, D. E. McClelland, and P. K. Lam, Squeezing in the Audio Gravitational-Wave Detection Band, Phys. Rev. Lett 93, 161105 (2004)
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Henning Vahlbruch ( Ph.D.Student
)
Boris Hage ( Ph.D. Student )
Andre Thüring ( Ph.D. Student )
Moritz Mehmet ( Ph.D. Student )