Force sensing based on coherent quantum noise cancellation in a hybrid optomechanical cavity with squeezed-vacuum injection

Abstract

We propose and analyse a feasible experimental scheme for a quantum force sensor based on the elimination of backaction noise through coherent quantum noise cancellation (CQNC) in a hybrid atom-cavity optomechanical setup assisted with squeezed vacuum injection. The force detector, which allows for a continuous, broadband detection of weak forces well below the standard quantum limit (SQL), is formed by a single optical cavity simultaneously coupled to a mechanical oscillator and to an ensemble of ultracold atoms. The latter acts as a negative-mass oscillator so that atomic noise exactly cancels the backaction noise from the mechanical oscillator due to destructive quantum interference. Squeezed vacuum injection enforces this cancellation and allows sub-SQL sensitivity to be reached in a very wide frequency band, and at much lower input laser powers.A different approach for sub-SQL measurements has recently been introduced [2, 3], based on the CQNC of backaction noise via quantum interference. The idea is based on introducing an 'anti-noise' path in the dynamics of the optomechanical system via the addition of an ancillary oscillator which manifests an equal and opposite response to the light field, i.e, an oscillator with an effective negative mass. In the context of atomic spin measurements an analogous idea for coherent backaction cancellation was proposed independently [31,32], and has been applied for magnetometry below the SQL [33], demonstrating that Einstein-Podolski-Rosen (EPR)-like entanglement of atoms generated by a measurement enhances the sensitivity to pulsed magnetic fields. The original proposal [2] focused on the use of an ancillary cavity that is red-detuned from the optomechanical cavity. A quantum non-demolition coupling of the electromagnetic fields within the two cavities yields the necessary anti-noise path, so that the backaction noise is coherently cancelled.[34] considered in more detail the all-optical realization of the CQNC proposal put forwarded in [2,3], and found that the requirements for its experimental implementation appear to be very challenging, especially for the experimentally relevant case of low mechanical frequencies and high-quality mechanical oscillators (MO) such as gravitational wave detectors. Other setups, which provide effective negative masses of ancillary systems for CQNC, have been suggested based on employing Bose-Einstein condensates [35], or the combination of a twotone drive technique and positive-negative mass oscillators [36].In recent years, hybrid optomechanical systems assisted by the additional coupling of the cavity mode with an atomic gas have attracted considerable attention. It has been found that the additional atomic ensemble may lead to the improvement of optomechanical cooling [37-41], thereby providing the possibility of ground state cooling outside the resolved sideband regime [42,43]. Moreover, the coupling of the mechanical oscillator to an atomic ensemble can be used to generate a squeezed state of the mechanical mode [44], or robust EPR-...

Force sensing beyond standard quantum limit with optomechanical “soft” mode induced by nonlinear interaction

“…When Eq(8) is further simplified with the limiting conditions g q g l = 0 and T = 0, it yields [3,13,14] S FF (ω)…”

Weak-force sensing with squeezed optomechanics

“…Linearization or even semiclassical approximation are standard effective descriptions applied in case of strong optical drives, which are valid in both theory [26,40] and experiments [15,73,74]. Indeed, a strong quantumoptical drive can usually be treated as a semiclassical parameter.…”

Absolute rotation detection by Coriolis force measurement using optomechanics

“…When thermal noise is neglected, the main contribution to the noise comes from the shot noise and the radiation pressure noise. To understand the origin of shot noise and radiation pressure noise, we substitute equations (32) and (26) in equation (33). Then the relation between the noise at the signal in equation (35) and the input noise operators d E and E v is given as The shot noise and the radiation pressure noise in equation (43) can be adjusted by the squeeze parameters f and r. Minimizing equation (43) with respect to f gives the optimum phase squeeze parameter f o , which is given as In equation (45), the shot noise and the radiation pressure noise goes ase r 2 [57], while the mirror noise is not effected by the squeezing.…”

“…This changes the length of the cavity and thus the optical response of the cavity itself. Optomechanical cavities are found to be extremely useful as displacement sensors [22][23][24][25] and as weak force sensors [26][27][28][29][30][31][32]. Recently, optomechanical systems have become a focus for a broad range of research activities [20,21] and several interesting phenomena like phase conjugation [33], squeezing [34], super-radiance [35], laser cooling [36][37][38], optomechanically induced transparency [39][40][41][42][43], etc, have been predicted in optomechanics.…”