Entangled photons have enabled experimental verification of foundations that underlie quantum theory. More recently they have become a resource for applications beyond the laboratory – specifically for quantum key distribution (QKD).
QKD uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random secret key, which can be used to encrypt and decrypt messages.
Free-space entangled photon experiments have taken place over more than a 100 kilometers and satellite relay is anticipated within a few years.
Air Force researchers have moved a step closer to quantum communication with the development of an optical system that can function to route or exchange entangled photon states and properties. Using a co-linear entangled source, the system selectively manifests frequency entangled or polarization entangled photons suited for secure QKD applications with shared keys and provable security.
It also enables a complete entangled state to be routed to either user by selecting the input frequencies to be both congruent, or incongruent. Unique features are selectable entanglement and routing, compact size, and integrated construction for telescopic compatibility.
- The technology utilizes birefringent filter stacks to preserve polarization correlations by recovering useful entanglement between photons exiting the hyperspectral filter stage and spatially direct it for further quantum information processing operations
- By controlling the frequency or the birefringence of the birefringent filter stack the hyperspectral filter stage acts as a routing switch
- The hyperspectral stage allows for routing intact an entangled pair in different directions, while maintaining the quantum entanglement between them
- US patent 9,664,566 available for license
- Potential for collaboration with Air Force researchers