Polarization stabilization scheme for a fiber-based Quantum Key Distribution device

IGNACIO LÓPEZ GRANDE; MIGUEL A. LAROTONDA

Mar del Plata

Congreso; Quantum Optics VII; 2014

Latin American Committee for Quantum Optics

We present the characterization and performance of a polarization stabilization scheme for a fiber-based Quantum Key Distribution device. The setup is based on two commercial  electro-optic polarization controllers and a detection scheme prepared to work within a classical (intense light) or photon counting regime.We show how to control the state of polarization of light, in particular we demonstrate a method to generate the set of polarization states that defines two MUBs needed for a standard BB84 protocol. In practical fiber implementations of QKD, the sender (Alice) and  receiver (Bob) are typically separated by kilometer distances. Due to unavoidable external perturbations the rotation induced by the fiber connecting the parties varies randomly with time. Thereforea mismatch between the input and output states of polarization naturally arises. The channel is stabilized by maximizing the overlap between the emitted and detected states. The optimization process is implemented with Arduino microcontrollers and additional 12-bit Digital to Analog converters. The performance of the device is evaluated by forcing sudden changes of the polarization on the fiber spool that connects the sender and receiver stations.