Observation of self-healing for single-photon space-time wave packets

Self-healing is a characteristic of structured optical fields in which the field structure is recovered rapidly after traversing an opaque obstruction. This feature has also been confirmed for a family of spatiotemporally structured light know as space-time wave packets (STWPs) synthesize from classical pulsed beams. Here we show that single-photon STWPs also demonstrate self-healing after traversing an opaque obstruction. We start with entangled photon pairs produced via spontaneous parametric downconversion. We detect the idler photon to herald the arrival of the signal photon, which traverses a spatiotemporal spectral modulator that yields a single-photon STWP. The propagation of the STWP is obstructed by an opaque slit, and the propagation of the single-photon field is monitored. We observe single-photon self-healing whose rate is enhanced by increasing the spatial bandwidth of the STWP.