Collision-resolved pressure sensing

While a continuous Brownian description of noise from heat and pressure is adequate to model measurements with relatively long integration times, these forces are ultimately generated by quantized degrees of freedom like phonons and gas particles. Fundamentally, the ultimate limit of this sensing problem is to resolve all of the individual system-sensor collisions. Here we propose the use of nanomechanical devices operated with impulse readout sensitivity around the standard quantum limit to sense ultralow gas pressures by directly counting the individual collisions of gas particles on a sensor. We illustrate this in two paradigmatic model systems: an optically levitated nanobead and a tethered membrane system in a phononic band-gap shield.