APPROFONDIMENTO

Entanglement-based QKD over 1,120 km

Entanglement-based QKD over 1,120 km
 

Quantum Key Distribution (QKD) is secure way of sharing cryptographic keys between remote users, leveraging on the quantum principles. The potential applications of QKD include not only securing communications networks but also critical infrastructures (for instance, the Smart Grid), transactions of financial institutions and national defense.
QKD has a TRL 7-9: there are some pieces of equipment already commercially available even if as today the distances covered over optical fibres are still relatively limited (about 50 to 80 km) owing to the channel loss that occurs when using optical fibres (or terrestrial free space) that exponentially reduces the photon transmission rate.
Long-distance entanglement distribution can be realized using quantum repeaters: on the other hand, the technology is still immature for practical implementations but there are intensive innovation activities. For example, innovation activities demonstrated the feasibility of QKD over a coiled optical fibre of about 500 km.
In satellite communications, longer distances have been achieved, owing to the negligible photon loss and decoherence experienced in empty space. Therefore, tj satellite-based QKD has the potential to help to establish a global-scale quantum network: for example, a 1,200 km point-to-point QKD has been already demonstrated from a satellite to a ground station, even if with limited efficiency.
Recently [1] entanglement-based QKD has been demonstrated between two ground stations over 1,120 km at a finite secret-key rate of 0.12 bits per second, without the need for trusted relays. In particular, entangled photon pairs were distributed via two bidirectional downlinks from the Micius satellite to two ground observatories in Delingha and Nanshan in China.

 

Torna all'articolo