Coherent Feedback Cooling of a Nanomechanical Membrane with Atomic Spins

Coherent feedback stabilises a system towards target state without the need of measurement, thus avoiding quantum backaction inherent to measurements. Here, we employ optical coherent remotely cool nanomechanical membrane using atomic spins as controller. Direct manipulation atoms allows us tune from strong-coupling an overdamped regime. Making use full control offered by our system, perform spin-membrane swaps combined with stroboscopic spin pumping in room-temperature environment ${T}={216}\,\mathrm{mK}$ ($\bar{n}_{m} = 2.3\times 10^3$ phonons) ${200}\,\mathrm{{\mu}s}$. We furthermore observe and study effects delayed on cooling performance. Starting cryogenically pre-cooled membrane, this method would enable mechanical oscillator close its ground preparation nonclassical states.