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Satellite-to-ground quantum-limited communication using a 50-kg-class microsatellite


The recent rapid growth of satellite-constellation programmes for remote sensing and communications, enabled by the availability of small-sized and low-cost satellites, has provided impetus for the development of high-capacity laser communication (lasercom) in space. Quantum-limited communication can enhance the performance of lasercom and is also a prerequisite for the intrinsically hack-proof secure communication known as quantum key distribution. Here, we report a quantum-limited communication experiment between a microsatellite (48 kg, 50 cm cube) in low Earth orbit and a ground station. Non-orthogonal polarization states were transmitted from the satellite at a 10 MHz repetition rate. On the ground, by post-processing the received quantum states with 0.146 photons per pulse, clock data recovery and polarization reference-frame synchronization were successfully achieved, even under remarkable Doppler shifts. The quantum states were discriminated by a receiver with four photon counters, with a quantum bit error rate below 5%, validating the applicability of our technology to satellite-to-ground lasercom and quantum key distribution.

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Figure 1: Transmitter and receiver systems.
Figure 2: Doppler shifts and frequency drifts in the optical link campaign on 5 August 2016.
Figure 3: Experimental results for bit pattern synchronization.
Figure 4: Experimental results on polarization angle variations and received power measured for Tx2 and Tx3 sequences.
Figure 5: Variation of the QBER in the emulated B92 protocol for a 1 min duration of 22:59:00–23:00:00 on 5 August 2016.


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The authors thank M. Akioka, T. Kubooka and H. Endo for their technical support on SOCRATES operation and data analysis. This work was supported in part by the ImPACT (Impulsing PAradigm change through disruptive Technologies) Program of the Cabinet Office of Japan.

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M.T., H.T., M.F. and M.S. conceived and designed the experiments. H.T., M.K. and M.F. performed the experiments. H.T., A.C.-C., M.K. and M.F. analysed the data. M.S. and A.C.-C. wrote the paper with discussions and input from all authors. M.T. and M.S. supervised the experiments.

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Correspondence to Masahide Sasaki.

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The authors declare no competing financial interests.

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Takenaka, H., Carrasco-Casado, A., Fujiwara, M. et al. Satellite-to-ground quantum-limited communication using a 50-kg-class microsatellite. Nature Photon 11, 502–508 (2017).

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