Secure multiparty quantum communication over telecom fiber networks

The paper reports on the first fiber quantum secret sharing experiment in three, four, and five-party implementations in the plug & play and Sagnac interferometer setups using single photons with phase encoding. A plug & play setup a secure secret sharing transmission distance of 66:1 km has been achieved for three-party with quantum bit error rate (QBER) of 7.1%; 40:5 km for four-party with QBER of 6:6%; and 6:7 km with QBER of 2:7%, suitable for local area network (LAN) applications, for five-party. In Sagnac interferometric setup, our experimental data in the three-party implementation show stable (in regards to birefringence drift) quantum secret sharing transmissions at the total Sagnac transmission loop distances of 55-75 km with the quantum bit error rates (QBER) of 2.3-2.4% for the mean photon number mu = 0.1 and 1.7-2.1% for mu = 0.3. In the four-party case a quantum secret sharing transmissions at the total Sagnac transmission loop distances of 45-55 km has been achieved with the quantum bit error rates (QBER) of 3.0-3.7% for the mean photon number mu = 0.1 and 1.8- 3.0% for mu = 0.3. The stability of quantum transmission has been achieved due to the new concept for compensation of SMF birefringence effects in Sagnac, based on a polarization control system and a polarization insensitive phase modulator.