Stable polarization coded quantum communication through single mode optical fibers

We perform a transmission of polarization encoded quantum bits through 16 km of single mode optical fiber in the 1550 nm window. The polarization drift caused by the changing birefringence of the fiber is kept stable through the use of a polarization control system we developed. This system employs 2 classical reference signals with 0.8 nm spacing from the quantum channel. We also send through the same fiber an extra reference classical signal used to trigger the single-photon detector. To the best of our knowledge this is the first time a quantum channel is multiplexed with 3 classical signals in the same optical fiber. However it is still desirable to perform quantum communication employing polarization coding. Phase coding systems require very good stabilization of the interferometers used, making polarization coding simpler in principle. There are other cases where polarization coding will be needed such as hyperentanglement [8]. In this paper we perform a stable transmission of polarization coded qubits, over 16 km of optical fiber and show the results.