Stable, low-error, and calibration-free polarization encoder for free-space quantum communication
Marco Avesani, Costantino Agnesi, Andrea Stanco, Giuseppe Vallone, Paolo Villoresi · Optics Letters · 2020
Polarization-encoded free-space quantum communication requires a quantum state source featuring fast modulation, long-term stability, and a low intrinsic error rate. Here we present a polarization encoder that, contrary to previous solutions, generates predetermined polarization states with a fixed reference frame in free-space. The proposed device does not require calibration either at the transmitter or at the receiver and achieves long-term stability. A proof-of-concept experiment is also reported, demonstrating a quantum bit error rate lower than 0.2% for several hours without any active recalibration.