Error filtration for quantum sensing via interferometry

Dephasing is a main noise mechanism that afflicts quantum information, it reduces visibility, and destroys coherence and entanglement. Therefore, it must be reduced, mitigated, and if possible corrected, to allow for demonstration of quantum advantage in any application of quantum technology, from computing to sensing and communications. Here we discuss a hardware scheme of error filtration to mitigate the effects of dephasing in optical quantum metrology. The scheme uses only passive linear optics and ancillary vacuum modes, without need of single-photon sources or entanglement. It exploits constructive and destructive interference to partially cancel the detrimental effects of statistically independent sources of dephasing. We apply this scheme to preserve coherent states and to phase-stabilize stellar interferometry, showing that a significant improvement can be obtained by using only a few ancillary modes.