Single-laser feedback cooling of optomechanical resonators

Measurement-based control has emerged as an important technique to prepare mechanical resonators in pure quantum states for applications in quantum information processing and quantum sensing. Conventionally this has required two separate channels, one for probing the motion and another one acting back on the resonator. In this work, we analyze and experimentally demonstrate a technique of single-laser feedback cooling, where one laser is used for both probing and controlling the mechanical motion. We show using an analytical model and experiments that feedback cooling is feasible in this mode as long as certain stability requirements are fulfilled. Our results demonstrate that, in addition to being more experimentally feasible construction, the interference effects of the single-laser feedback can actually be used to enhance cooling at some parameter regimes.