Quantum Optics Seminar by Michael R. Vanner – Niels Bohr Institute - University of Copenhagen

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Quantum Optics Seminar by Michael R. Vanner

“Quantum optomechanics” is one of the newest and most rapidly growing branches of continuous­variable quantum optics, offering significant potential to contribute to research areas such as quantum measurement and control, quantum decoherence, and non‐classical state preparation of macroscopic objects. The field utilises the radiation‐pressure interaction and our ability to prepare and measure the quantum properties of light to manipulate the motion of micro‐or nano‐fabricated mechanical resonators. A current major goal of the field is to be able to perform precise measurements of non‐linear degrees‐of‐freedom of mechanical motion, which provides a route for non‐Gaussian quantum state preparation by measurement. In this talk, I will describe an approach how to perform measurements of the mechanical position squared by exploiting the optical non­linearity of the radiation‐pressure interaction [1]. I will also describe the results of a recent experiment employing this approach that we performed in Brisbane [2] that made the first observations of mechanical displacement squared thermal motion, which we utilised for conditional non‐Guassian motional state preparation at a classical level. Our measurement strengths are orders of magnitude larger than the best predicted values with the “membrane‐in‐the‐middle” approach [3] that has a mechanical position squared Hamiltonian coupling. Future improvements to our displacement squared measurement sensitivity and operation at cryogenic temperatures will allow the preparation of mechanical Schrödinger‐cat states of motion.

[1]   M. R. Vanner, “Selective Linear or Quadratic Optomechanical Coupling via Measurement” Phys. Rev. X 1, 021011 (2011).

[2]   G. A. Brawley, M. R. Vanner, etal., manuscript in preparation (2013).

[3]  J. C. Sankey, etal., “Strong and tunable nonlinear optomechanical coupling in a low‐loss system” Nature Physics, 6 707 (2010).