Cooling by measurement
23. Aug 2013 — Observing a physical quantity without disturbing it is a key capability for the control of individual quantum systems. Such back-action-evading or quantum non-demolition measurements were first introduced in the 1970s for gravitational wave detection, and now such techniques are an indispensable tool throughout quantum science.
Copyright: University of Vienna
Researchers of the University of Vienna have now implemented a back-action-evading interaction for measuring the position of a micromechanical oscillator. Following a scheme that they had suggested two years ago [PNAS USA 108, 16182 (2011)] Michael Vanner and colleagues use pulses of light with a duration much shorter than a period of mechanical motion, which allows state preparation and full state tomography of the mechanical motional state. They have reconstructed mechanical states with a position uncertainty reduced to 19 pm, limited by the quantum fluctuations of the optical pulse, and they have performed ‘cooling-by-measurement’ to reduce the mechanical mode temperature from an initial 1,100 K to 16 K. Future improvements to this technique will allow for quantum squeezing of mechanical motion, even from room temperature, and reconstruction of non-classical states exhibiting negative phase-space quasi-probability.
M. R. Vanner, J. Hofer, G. D. Cole, M. Aspelmeyer
Nature Communications 4, 2295 (2013)