Quantum keys managed to pass on 200 km

Quantum cryptographers from NIST have announced yet another record achievement. They managed to successfully transmit single photons (from them the so-called "quantum keys" are created) to a distance of 200 km via ordinary optical fiber. The experiment used mainly standard equipment (with the exception of a special detector created at Moscow State Pedagogical University), and the transmission was carried out at a standard frequency. Thus, quantum cryptography has come close to full-scale commercial use in Internet applications.

The results of the experiment are described in detail in a scientific article in the journal Nature Photonics (paid access).

In addition to a new range record, in the Stanford experiment, photons were generated and transmitted for the first time at such a high frequency of 10 GHz. These photons were used to produce quantum keys. Such keys have unsurpassed reliability, because, due to the nature of photons, it is even theoretically impossible to intercept or “spy” them during transmission. Thus, quantum keys have guaranteed reliability according to the laws of physics.

Scientists from Stanford admit that a unique photon detector created at Moscow State Pedagogical University has become a key element in setting a record. A detector with a superconducting nanowire of niobium nitride (it captures photons) is capable of very quickly and reliably process billions of particles. The Americans designed a cryogenic cooling system for the detector up to -270 ° C to ensure a low level of interference and minimize the number of false alarms. The detector has been successfully connected to the fiber optic line.

via NIST , Nature Photonics