Note: Interference technique for minimally invasive, subnanometer, microsecond measurements of displacements

We present a novel high-resolution technique for single-molecule experiments, viz., differential traveling wave tracking. This is an interference-based scattering technique where we use gold nanoparticles for high scattering intensities and incorporate differential measurements along one in-plane direction to subtract mechanical noise and drift of the system. In addition, out-of-plane distances are measured via scattered light intensity in a total internal reflectance illumination field. In plane, we demonstrate a rms noise level of only 0.10 nm at 10 kHz and less than 0.5 nm at 600 kHz.