Quantum non-demolition stroboscopic observables and multipumping back-action evasion schemes

Roberto Onofrio

Shang Song, Carlton M. Caves, Bernard Yurke

健太郎 宗宮, Kentaro Somiya

Franco Bordoni, Roberto Onofrio

A technique is proposed to improve the squeezing of the mechanical noise in a back-action evasion measurement. The scheme is based on the use of a parametric multipump system and, in the limit of many pump components, approaches a stroboscopic measurement. A simple model of the back-action evasion effect for this scheme is developed. Experimental evidence of a significant increase in the squeezing with respect to the two-pump scheme and in accordance with the model is reported.

Franco Bordoni, Roberto Onofrio

A technique is proposed to improve the squeezing of the mechanical noise in a back-action evasion measurement. The scheme is based on the use of a parametric multipump system and, in the limit of many pump components, approaches a stroboscopic measurement. A simple model of the back-action evasion effect for this scheme is developed. Experimental evidence of a significant increase in the squeezing with respect to the two-pump scheme and in accordance with the model is reported.

Zhiyuan Dong, Weichao Liang, Guofeng Zhang

We establish a framework for realizing back-action-evading (BAE) measurements and quantum non-demolition (QND) variables in linear quantum systems. The key condition, a purely imaginary Hamiltonian with a real or imaginary coupling operator, enables BAE measurements of conjugate observables. Symmetric coupling further yields QND variables. For non-compliant systems, coherent feedback is designed to engineer BAE measurements. Crucially, the QND interaction condition simultaneously ensures BAE measurements and promotes the coupling operator to a QND observable.