Tomography of a Mode-Tunable Coherent Single-Photon Subtractor

Understand

Single-photon subtraction plays important roles in optical quantum information processing as it provides a non-Gaussian characteristic in continuous-variable quantum information.

• While the conventional way of implementing single-photon subtraction based on a low-reflectance beam splitter works properly for a single-mode quantum state, it is unsuitable for a multimode quantum state because a single photon is subtracted from all multiple modes without maintaining their mode coherence.
• Here we experimentally implement and characterize a mode-tunable coherent single-photon subtractor based on sum frequency generation.
• It can subtract a single photon exclusively from one desired time-frequency mode of light or from a coherent superposition of multiple time-frequency modes.