With all the hype around China’s quantum teleportation breakthrough, the world scarcely noticed that around the same time, Japan achieved a similar feat with a microsatellite.
Japan’s National Institute of Information and Communications Technology (NICT) announced on 11 July 2017 that it has successfully demonstrated the first quantum-communication experiment from space, by sending information from a microsatellite to a ground station using a single photon regime.
The single photon regime was transmitted from Japan’s microsatellite Socrates, which weighs 48kg and was launched from Tanegashima in 2014. An experimental satellite, Socrates’ main payload is SOTA (Small Optical TrAnsponder), which is the world’s smallest and lightest quantum-communication transmitter weighing only 6kg.
SOTA is programmed to transmit a laser signal to the ground at a rate of 10 million bits per second, from an altitude of 600 km and a speed of 7 km/s. This single was detected at the NICT optical ground station in Tokyo’s Koganei city, using a 1-m telescope, although NICT admitted that the signal is very weak.
There are several differences between Japan’s experiment and China’s quantum teleportation one, aside from the size of the satellites. Although both use telescopes to receive the photons, Japan’s photons are transmitted from the satellite to the ground, whereas China’s are ground-to-satellite. Also, the NICT experiment does not involve quantum entanglement, and therefore cannot be said to “teleport” the photons, but instead opens up the possibility of using low-cost satellites to achieve secure quantum networks.
Japan and China are currently the only countries in the world able to accurately time-stamp the signals, so that they are clearly recognized in the quantum receiver. This means that the receiver can be certain that the signal is from the satellite and vice versa, rather than random ones from unknown sources, and is crucial to communication.
Similar experiments have been conducted by Singapore and Germany, with the European Space Agency (ESA) and NASA soon to join what is termed the “Quantum Space Race”.