Quantum keys managed to pass on 200 km

NIST quantum cryptographers have announced another record break. They were able to successfully transfer single photons (of which so-called “quantum keys” are being created) to a distance of 200 km over ordinary optical fiber. In the experiment, mainly standard equipment was used (the exception is a special detector created at the Moscow State Pedagogical University), and the transmission was carried out on a standard frequency. Thus, quantum cryptography is very 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 the new range record, the Stanford experiment was the first to generate and transmit photons 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 the photons, it is even theoretically impossible to intercept or “spy” them during the transfer process. 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 the key element in setting the record. A detector with superconducting niobium nitride (the one that captures photons) can process billions of particles very quickly and reliably. The Americans designed a cryogenic cooling system for the detector to -270 ° C in order to ensure a low level of interference and minimize the number of false alarms. The detector has been successfully connected to a fiber optic line.
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via NIST , Nature Photonics