The laboratory system produced this “raw” key at a rate of more than 4 million bits per second (4 million bps) over 1 kilometer (km) of optical fiber, twice the speed of NIST’s previous record, reported just last month.** The system also worked successfully, although more slowly, over 4 km of fiber.
The record speed was achieved with an error rate of only 3.6 percent, considered very low. The next step will be to process the raw key, using NIST-developed methods for correcting errors and increasing privacy, to generate "secret" key at about half the original speed, or about 2 million bps. The NIST quantum key distribution (QKD) system uses single photons, the smallest particles of light, in different orientations to produce a continuous binary code, or "key," for encrypting information. The rules of quantum mechanics ensure that anyone intercepting the key is detected, thus providing highly secure key exchange.