CQuIC Seminars
Quantum mechanics in the negative mass reference frame
Presented by Eugene Polzik, University of Copenhagen
Quantum mechanics dictates that a continuous measurement of a position of an object imposes a random back action perturbation on its momentum. This randomness translates with time into position uncertainty, thus leading to the well-known uncertainty on the measurement of motion. As proposed in [1-3], a measurement of motion with precision beyond the vacuum state uncertainty in both position and momentum is possible if it is carried out in a quantum reference frame with an effective negative mass. In such a measurement, the quantum back action is evaded due to the destructive interference of the back action on the object and on the reference frame. Such a reference frame can be implemented with an oscillator which has its first excited state energy below the ground state energy, e.g., an atomic spin oscillator oriented along the magnetic field [4].
In the talk I will outline the basic steps towards back action free measurements, describe the experiment where a hybrid spin-mechanical system is probed by light, and present an experimental demonstration of quantum back action evasion [5]. The two macroscopic oscillators are a millimeter size dielectric membrane [6] and a long lived collective spin of an atomic ensemble [7] positioned at a meter distance. The negative mass reference frame physics opens the way towards generation of entanglement between mechanical and spin oscillators, leading to applications in fundamental physics of entangled macroscopic objects, and to force, gravitation and acceleration measurements beyond standard quantum limits.
[1] K. Hammerer, M. Aspelmeyer, E.S. Polzik, P. Zoller. Phys. Rev. Lett. 102, 020501 (2009).
[2] M. Tsang and C. Caves, Phys. Rev. Lett. 105(12), (2010).
[3] E. S. Polzik and K.Hammerer. Annalen der Physyk. 527, No. 1-2, A15-20 (2015).
[4] W. Wasilewski et al. Phys. Rev. Lett. 104, 133601 (2010).
[5] C. Muller, R. Thomas, G. Vasilakis, E. Zeuthen, Y. Tsaturyan, K. Jensen, A. Schliesser, K. Hammerer and E. S. Polzik. Submitted for publication.
[6] Y. Tsaturyan et al. Optics Express, Vol. 22, Issue 6, pp. 6810-6821 (2014).
[7] G. Vasilakis et al. Nature Physics, doi:10.1038/nphys3280 (2015).
4:00 pm, Wednesday, January 11, 2017
PAIS-2540, PAIS
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