Duration: 12 months
Optical frequency band is expected to play an increasingly important role in space communications. The benefit of substantially higher data rates is complemented by enhanced security. At the basic level, data-carrying optical beams experience much lower diffraction compared to the radio frequency band and hence can be detected only within much smaller spatial region. The physical layer security can be further improved using techniques of key distribution exploiting quantum noise and quantum mechanical uncertainty relations.
The background noise collected by the receiver limits the performance of optical communication systems operated at low signal powers, e.g. in the photon-starved regime typical to deep-space communication and quantum key distribution protocols with single photons. The conventional technique of narrowband spectral filtering of the received signal followed by temporal gating does not allow one to select in a lossless manner the signal mode (waveform) from the remaining background noise, see e.g. [1] M. G. Raymer and K. Banaszek, Opt. Express 28, 32819 (2020).
Genuine single-mode filtering can be achieved using the recently demonstrated quantum pulse gate (QPG) technique which relies on carefully engineered sum-frequency generation in a chi(2) nonlinear optical medium. With an appropriate choice of the medium phase matching function and the duration of the pump pulse, QPG upconverts only a single temporal mode from the signal beam, leaving the remaining noise at the input frequency. An additional advantage of QPG may be more convenient carrier frequency for single-photon detection.
The purpose of the proposed activity is to explore quantitatively the feasibility of the QPG technique for space optical communication systems. This will involve analysis of signal characteristics for which a QPG device can operate efficiently, comparison with space optical communication standards and system specification for a proof-of-concept validation of the idea.
