Quantum Optics Seminar by Nir Kampel – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Nir Kampel

We have developed an optomechanical system composed of a high-Q, high-stress silicon nitride membrane inside a high-finesse cavity as a tool for quantum measurement studies. We can access a limit in which membrane resonator position fluctuations are strongly driven by the quantum fluctuations of light, i.e. are dominated by the measurement  back-action necessitated by the Heisenberg uncertainty relation. The correlation between the quantum fluctuations of the coherent light probe and the easurement backaction gives rise to a variety of quantum effects. 

 Here I’ll present our recent results on three different experiments.  In the first experiment, we show squeezing of 1.7dB (32%) below shot noise of the light exiting the cavity using the above correlations

 [1]. In the second experiment, we measure a single quadrature that is unaffected by the back-action that appears in the orthogonal quadrature [2], and thus increase the sensitivity of a force or displacement measurement. We realize this measurement by using a combination of two optical probe tones to modulate the measurement strength at an appropriate frequency [3]. 

 In the third experiment we test a membrane surrounded by a phononic   crystal. The phononic crystal minimizes the acoustic coupling between the membrane and its supporting structure. We show that the membrane isolation is improved by about 30dB, due to the phononic bandgap [4]. 

 [1] T. P. Purdy, P.-L. Yu, R. W. Peterson, N. S. Kampel, and C. A.  Regal, PRX, 3, 031012 (2013).

 [2] V. B. Braginsky, Y. I. Vorontsov, K. S. Thorne, Science, 209, 547  (1980).

 [3] J. B. Hertzberg, T. Rocheleau, T. Ndukum, M. Savva, A. A. Clerk and K.

 C. Schwab, nature physics, 6, 213 (2010).

 [4] P.-L. Yu, K. Cicak, N. S. Kampel, Y. Tsaturyan, T. P. Purdy, R. W.

 Simmonds, APL, 104, 023510 (2014).