Space-to-Ground Quantum Key Distribution Using a Small-Sized Payload on Tiangong-2 Space Lab

Abstract

Quantum technology establishes a foundation for secure communication via quantum key distribution (QKD). In the last two decades, the rapid development of QKD makes a global quantum communication network feasible. In order to construct this network, it is economical to consider small-sized and low-cost QKD payloads, which can be assembled on satellites with different sizes, such as space stations. Here we report an experimental demonstration of space-to-ground QKD using a small-sized payload, from Tiangong-2 space lab to Nanshan ground station. The 57.9-kg payload integrates a tracking system, a QKD transmitter along with modules for synchronization, and a laser communication transmitter. In the space lab, a 50 MHz vacuum + weak decoy-state optical source is sent through a reflective telescope with an aperture of 200 mm. On the ground station, a telescope with an aperture of 1200 mm collects the signal photons. A stable and high-transmittance communication channel is set up with a high-precision bidirectional tracking system, a polarization compensation module, and a synchronization system. When the quantum link is successfully established, we obtain a key rate over 100 bps with a communication distance up to 719 km. Together with our recent development of QKD in daylight, the present demonstration paves the way towards a practical satellite-constellation-based global quantum secure network with small-sized QKD payloads.

Satellite-mediated quantum atmospheric links

“…The recent success in practical realization of quantum state transfer between satellites and ground stations [1][2][3][4][5][6][7][8][9][10][11] has established the cornerstone of future global quantum communication. This achievement is especially impressive in the view of how fast the quantum communication over free-space quantum links reached its maturity.…”

Quantum Key Distribution

“…Nevertheless, the results obtained from experiments in Los Alamos [17] and Munich in which a link between the ground and an aircraft flying at 290 km/h was established [18] demonstrated promise with satellite connections [17][18][19][20][21][22][23]. After performing a sequence of free space QKD experiments on the ground, China successfully launched the quantum satellite "Micius," which demonstrated a satellite-to-ground QKD over a distance of 645 to 1200 kilometers [24].…”

“…These efforts started by constructing testbed metropolitan QKD networks in Hefei, where a three-node network [115] and five-node network [71] were constructed in 2009 and 2010, respectively. Other efforts to construct fiber-based QKD networks have been reported in References [116][117][118][119], and a satellite-based QKD network is also being formed [24]. This section provides an overview of these developments by looking at some recently constructed fiber-based networks.…”

“…24-km link between the Otemachi and Hakusan nodes was provided by the Mitsubishi Electric Corporation and NTT Company. They implemented the BB84 protocol with a maximum key rate of 2 kbps and QBER of 4.5%.• A 45-km link between the Koganei and Otemachi nodes was provided by NEC, implementing the decoy state BB84 protocol with a NICT superconducting single photon detector (SSPD).…”

Analysis of atmospheric effects on satellite-based quantum communication: a comparative study

“…These laser pulses contain single photons by emitting pulses of low optical power, which results in only a single photon from the source. Decoy pulses must be deployed to avoid the side channel attack due to multi photons per pulse [36,44,50,52,63,64,[89][90][91][92].…”