Enhanced entanglement of two different mechanical resonators via coherent feedback

Abstract

It was shown [New J. Phys. 17, 103037 (2015)] that large and robust entanglement between two different mechanical resonators could be achieved, either dynamically or in the steady state, in an optomechanical system in which the two mechanical resonators are coupled to a single cavity mode driven by a suitably chosen two-tone field. An important limitation of the scheme is that the cavity decay rate must be much smaller than the two mechanical frequencies and their difference. Here we show that the entanglement can be remarkably enhanced, and the validity of the scheme can be largely extended, by adding a coherent feedback loop that effectively reduces the cavity decay rate

Upper Bounds on Spontaneous Wave-Function Collapse Models Using Millikelvin-Cooled Nanocantilevers

“…Here, we demonstrate for the first time this method, by accurately measuring the mean energy of a nanocantilever in thermal equilibrium at millikelvin temperatures. We infer an experimental upper bound on λ, which is 2 orders of magnitude stronger than that set by matter-wave interferometry [20][21][22] for r C ¼ 10 −7 m, and the strongest one to date for r C > 10 −6 m. Theoretical model.-The detection of CSL-induced heating in realistic optomechanical systems has been extensively discussed in the recent literature [15][16][17][18][19]. Here we summarize the main steps.…”

“…11AE2 times larger at r C ¼ 10 −6 m. The direct effect of collapse models like CSL is to destroy quantum superpositions, resulting in a loss of coherence in interferometric tests with matter-wave [6][7][8] or mechanical resonators [9][10][11]. Recently, noninterferometric tests have been proposed, which promise to set stronger bounds on these models [12][13][14][15][16][17][18][19]. Among such tests, the measurement of heating effects in mechanical systems, a byproduct of the collapse process, seems particularly promising [15][16][17][18].…”

“…Recently, noninterferometric tests have been proposed, which promise to set stronger bounds on these models [12][13][14][15][16][17][18][19]. Among such tests, the measurement of heating effects in mechanical systems, a byproduct of the collapse process, seems particularly promising [15][16][17][18].…”

“…Macroscopic lowfrequency resonators such as gravitational wave detectors [39,40] are not effective as well, because of the very large size [16,17]. A more promising approach is given by resonators with much lower resonant frequency, such as torsion microbalances or micropendula [41] or by levitated microparticles [18,19,42].…”

Arbitrary multimode Gaussian operations on mechanical cluster states

“…In fact, various theoretical analyses of multiple resonators coupled to radiation pressure have been put forward [41][42][43][44][45][46][47][48][49][50][51][52]. In particular, a recent proposal showed that arbitrary graph states may be generated in an array of resonators immersed in a cavity field [53] using a generalisation of the reservoir engineering sometimes used for cooling [19,21,37,54].…”