Performing remote phase measurements with a sensitivity proportional to the intensity of light that never interacted with distant, and possibly delicate, samples. On the front cover of Advanced Quantum Technologies, December 2022.
We demonstrate remote phase estimation of a distant sample (the cell in the background of this pictorial representation) with a sensitivity that only depends on the intensity of light that never interacted with it. This is made possible by the extreme fragility of the entanglement produced between two laser pulses (in the foreground) via coherent addition of a single photon, which strongly depends on the relative phase between two single-photon-level pulses in the distant heralding station, where the sample is placed.
