Emma Tien Hwai Medlock

This poster presentation demonstrates the quantum random number generation (QRNG) from a shotnoise-limited homodyne detector. The detector is part of the continuous variable quantum key distribution (CVQKD) payload developed for the Satellite Platform for Optical Quantum Communications (SPOQC) mission. We also show how the onboard homodyne detector works as a CVQKD receiver on the satellite.

Continuous variable quantum key distribution (CV-QKD) uses modulation of amplitude and phase of electromagnetic fields to encode information and shot noise limited detectors for decoding. The shot noise limited detection shows superior tolerance to noise and therefore a promising candidate for space-to-ground quantum communications, especially in daylight conditions. The parameters that affect the secure key generation rate of CV-QKD systems are the channel parameters- transmittance and uncalibrated noise (excess noise). On a typical static channel, such as an optical fibre link, the channel transmittance stays constant over a long period of signal transmission. On a dynamic channel, such as a Low Earth Orbit (LEO) based satellite to ground optical link, the transmittance of the channel varies concerning the zenith angle of the satellite.

We consider passive eavesdropping in continuous-variable quantum key distribution (CV-QKD) over atmospheric turbulence channels. We study the effect of turbulence in creating independent channels from Alice to Bob and Eve, and examine the performance of transmitted local oscillator (TLO) and local local oscillator (LLO) based CV-QKD system.