Fast optical source for quantum key distribution based on semiconductor optical amplifiers

Fast optical source for quantum key distribution based on semiconductor optical amplifiers

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Preview: M.Jofre 1,∗,A.Gardelein 1,W.Amaya 2,J.Capmany 2,R.Ursin 3,4 ,L. Peñate 5, D.Lopez 5, J.L.SanJuan 6, J.A.Carrasco 7, F.Garcia 7, J. Torcal 8, L.M.Sanchez-Brea 8, E.Bernabeu, J.M.Perdigues, T. Jennewein, G.Anzolin 1, J.P.Torres 1,11, M.W.Mitchell 1,V. Pruneri 1,12 1, ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels (Barcelona), Spain 2 Institute of Telecommunications and Multimedia Applications (ITEAM), Universidad Politécnica de Valencia, Spain 3 Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Austria 4 Faculty of Physics, University of Vienna, Austria 5 ALTER Technology Group, Spain 6LIDAX, 28850 Torrejón de Ardoz, Spain 7 EMXYS, 03206 Elche, Spain 8 Departamento de Optica, Universidad Complutense de Madrid, 18040 Madrid, Spain 9 European Space Agency, Noordwijk, The Netherlands 10Institute for Quantum Computing, University of Waterloo, Canada 11 Department of Signal Theory and Communications, Universitat Politécnica de Catalunya, Spain 12 ICREA-Instituci´o Catalana de Recerca i Estudis Avanc¸ats, 08010 Barcelona, Spain marc.jofre@icfo.es

Schematic of the QKD source a semiconductor optical amplifier

Fig.1 Schematic of the QKDsource.[LD] denotes a laser diode,[C] a single-mode in-fiber 1×2 coupler, [SOA] a semiconductor optical amplifier, [P] a free-space thin-film polarizer and [BF] a single-mode bare fiber.

Abstract: A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level indistiguishability in time and spectrum of the pulses with the four different polarizations and three different levels of intensity.

The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state protocol. A lower bound secure key rate of the order of 1.82 Mbps and a quantum bit error ratio as low as 1.14×10−2 and 93 bps for an equivalent attenuation of 35 dB were achieved.

To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.