Quantum sensors and memories based on soft-clamped phononic membrane resonators

Soft-clamped phononic membrane resonators achieve coherence times exceeding 100 ms and force sensitivity in the zepto-Newton range. With such devices, we measure force and displacement at and beyond the standard quantum limit, and control the motional quantum state, even at room temperature. As an application example, we image individual viruses and nanoparticles using the membrane as a force sensor. In a different set of experiments, we demonstrate mechanical storage and subsequent retrieval of optical pulses with an efficiency of 40%, suggesting applications as quantum memory for light.