Joshua Bienfang

In a significant scientific breakthrough, National Institute for Standards and Technology (NIST) Physicist Joshua Bienfang has created a new way to send and receive encrypted messages that are 100 percent secure and transmitted at record speeds using existing high-speed telecommunications technology.

The cutting-edge achievement, relying on quantum physics, has potential implications for national security, the military, medical records privacy and commerce.

“What Josh has done is create a system that is absolutely secure—where you can be sure based on the most well understood laws of physics that no one has intercepted the message,” said William Phillips, a NIST Fellow and 1997 Nobel Prize recipient for physics.

“It’s a new way of thinking for how to secure communications. There’s a real practical application for his work,” added Charles Clark, chief of NIST’s electron and optical physics division.

Quantum cryptography relies on the transmission of single particles of light – photons – between sender and recipient. The quantum nature of the photons allows the users to detect eavesdropping because measurement of their properties changes their state. Thus quantum physics prohibits eavesdroppers from reading a photon and passing it on without detection.

Quantum cryptography was first demonstrated in the laboratory in the 1980s and had largely been viewed as an experimental field due to a variety of practical difficulties. Subsequent efforts around the world had been pursued and demonstrated practical implementation of quantum cryptography. Bienfang was the first to apply modern telecommunications architecture to demonstrate quantum cryptography with extremely high transmission rates.

To support high-speed operation he employed a method known as free-space optical (FSO) communication, in which the single-photon signals are sent through the open air between transmitters and receivers using telescopes. Although deployed as a commercial technology for Internet service provision and enterprise local area networks, quantum cryptography at such rates had never been demonstrated over a FSO channel.

Bienfang’s adaptation of FSO to high-speed quantum communications confronted a range of challenges not previously addressed: the development of sources and single-photon detectors that could support gigahertz frequencies (a billion times per second); the synchronization to within 50 trillionths of a second of the transmitter and receiver apparatus that were separated by about a mile; design and construction of the custom-built high-speed electronics needed to control the operation of the system; and development of high-speed real-time algorithms to perform essential cryptographic functions such as key distillation and privacy amplification.

The system he and his colleagues developed has set several world speed records for transmission of a secure quantum cryptographic key—showing, for example, that it is possible to perform full quantum encryption of streaming video in applications such as YouTube. This high-speed approach has been adopted by many other scientists in the field.

“When he started, this technology didn’t exist,” said Phillips. “The ideas existed, but he reduced it to practice so that it would actually be useful.”

Phillips noted that currently there are many good ways of encrypting information, but he pointed out that developments in computers will make today’s standard forms of encryption useless. He said the system developed by Bienfang is unique because it uses “the weirdness of quantum mechanics” to do something useful that could stand the test of time.

Bienfang said that the work, funded in part by the Defense Advanced Research Projects Agency, lies at the intersection of quantum physics and information technology.

“The merger of those two fields will yield unique technological capabilities,” Bienfang said. “As a scientist, I was just excited to get involved in something that I thought would be relevant and important and certainly at the forefront of modern technology”.

Like many scientific developments in the past, he said, “one doesn’t know what the final application of a new tool or technology will be.”

Clark said Bienfang’s quantum physics work also could be applied to biological microscopy, very sensitive images of stellar objects, and secure high-speed data processing. Clark also said there have been public disclosures that the military is “working on using quantum communication to send cryptographic keys to satellites.”

“He does work that is really inspirational in its scope,” Clark said. “Many people have this image of federal work as mundane or overly bureaucratic, and here is this guy who is doing this cutting-edge, exciting work and is very enthusiastic about it. He’s a great face for the federal workforce.”