Quiness

The Department of Defense requires secure communications, but the broad availability of advanced communications technology possessed by adversaries makes it increasingly difficult to ensure the integrity and confidentiality of DoD information. The science of quantum communications—in which single photons from entangled photon pairs are transmitted over a distance—offers the possibility of unconditionally secure communication because the act of measuring a quantum object changes it. For quantum communications to be practical, however, several technological barriers must be overcome.

Quantum communications have traditionally operated at low data rates because they relied on the transmission of fragile single-photon states which are extremely sensitive to loss and noise, and for which no high sensitivity, high efficiency, high data rate single photon detectors exist. As a result, contemporary quantum communications are limited to short distances and low data rates. In contrast, classical telecommunications are capable of extremely high data rates (measured in gigabits per second) and long distances (more than 1000 kilometers). DARPA created the Quiness program to investigate novel technologies capable of high-rate, long-distance quantum communications.

Quiness is exploring a variety of approaches to improving quantum communications, including:

• coupling single-photon states or few-photon states to bright optical states for long-distance transmission;
• theoretical constructs and protocols which can extend the reach and rate of more traditional quantum approaches;
• new types of quantum repeaters; and
• novel encodings which allow photonic states to transfer additional quantum information.

Success in this effort would enable secure, point-to-point DoD communications and could support development of a quantum network in which secure information could be shared between one point and many.