Quantum Optics Colloquium by Rodrigo Thomas – University of Copenhagen

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Quantum Optics Colloquium by Rodrigo Thomas

Quantum back-action evasion and entanglement in a hybrid spin-mechanical system

The ultimate limits of sensitivity in a continuous measurement of canonically conjugate variables are set by the rules of Quantum Mechanics. This limit is due to the fundamental trade off between measurement imprecision and induced back-action on the system under investigation. However, as theoretically and experimentally previously shown in [1,2], if the measurement is performed in a negative mass reference frame, the back-action effect can be evaded.

In this talk, I will present the recent efforts towards establishing a hybrid quantum interface between an atomic spin ensemble and a nanomechanical resonator. Our demonstration of quantum back-action evasion [3] sets the stage for entanglement generation [4] and enhanced precision for gravitational wave detectors [5].


[1] K. Hammerer, et al, "Establishing Einstein-Poldosky-Rosen Channels between Nanomechanics and Atomic Ensembles", PRL 102, 020501 (2009).

[2] B. Julsgaard, et al, "Experimental long-lived entanglement of two macroscopic objects", Nature 413, 400–403 (2001).

[3] C.B. Møller*, R.A. Thomas*, et al, "Quantum back-action-evading measurement of motion in a negative mass reference frame", Nature 547, 191-195 (2017).

[4] X. Huang, et al, "Unconditional steady-state entanglement in macroscopic hybrid systems by coherent noise cancellation", arXiv:1801.02569 (2018).

[5] F. Khalili, et al, "Overcoming the standard quantum limit in gravitational wave detectors using spin systems with a negative effective mass", arXiv:1710.10405 (2017).