PORTLAND, Ore. Government laboratories are claiming a new distance record for an emerging encryption scheme called quantum key distribution.
The National Institute of Standards and Technology (NIST), which performed the work in collaboration with Los Alamos National Laboratory and Albion College (Albion, Mich.), said it achieved a hack-proof distance of 184.6 kilometers between two fast Ethernet networks.
Quantum key distribution enables hack-proof communications, eliminating the possibility of eavesdropping. Rather than depending on encryption key length to scramble transmitted data, quantum cryptography creates uncrackable codes that employ the laws of physics to guarantee security.
Different quantum states encoded using photon polarization are used to represent ones and zeroes in such a way that intrusions can be detected. For instance, if a hacker viewed a polarized photon, the intrusion would switch that bit in the key, thereby alerting the recipient to an eavesdropping attempt.
Quantum key distribution requires single-photon emitters and receivers. NIST operates a Quantum Communication Testbed that can exchange quantum keys over a free-space link. NIST said the distance record, achieved in a laboratory in Bolder Colo., was made possible by a new type of detector that uses a tungsten film cooled to the superconducting transition temperature, exhibiting nearly resistance-free performance. In that state, a single photon striking the tungsten caused its electrical resistance to rise dramatically.
NIST also said the sensor could be used to determine how many photons were present in a light pulse by measuring temperature changes.
NIST claims its super-cooled tungsten sensor is more efficient, produces fewer false counts and recovers in just four microseconds, permitting quantum keys to be changed up to 250,000 times per second. NIST said commercial photon detectors have better timing resolutionless than 100 picoseconds compared to NIST's 100 nanosecondsbut it expects to improve system electronics to reduce jitter on future designs.
The research was funded by the Defense Advanced Research Projects Agency, the National Security Agency and through a CIA postdoctoral program.