Abstract: A fiber ring resonator having a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface.

Abstract: A fiber ring resonator having a relatively long loop of standard single-mode fiber with a short nanofiber segment. The evanescent mode of the nanofiber segment allows the cavity-enhanced field to interact with atoms in close proximity to the nanofiber surface.

Abstract: Quantum key distribution QKD systems and methods are provided that allow for QKD over distances not previously achievable. In one embodiment, the QKD system and method utilizes state discrimination techniques. In another embodiment, the QKD system and method utilizes amplifiers and unitary transformations to extend the range over which QKD can be achieved. The QKD systems and methods of the present invention can be used to implement secure quantum communications systems.

Abstract: Techniques are provided for placing atoms inside an appropriate nanocavity for enhancing two-photon absorption and quantum information processing based on the Zeno effect. Techniques for fabricating suitable nanocavities include: 1) a short length of optical fiber polished on the ends with the ends coated to form suitable mirrors; 2) a continuous length of fiber with the equivalent of mirrors being formed within the fiber using Bragg gratings; 3) a single filament of glass (such as fused silica) being suspended between two mirrors (without any cladding) and surrounded by an atomic vapor, solid, or liquid; 4) a small glass sphere (such as fused silica) that has been melted on the end of an optical fiber; and 5) a small toroid (ring) of glass bent in a circle surrounded by suitable atoms.

Abstract: An optical switch and optical storage loop are used as the basis of a single-photon source and a quantum memory for photonic qubits. To operate as a single-photon source, the techniques include a source of a pair of photons, such as a parametric down-conversion crystal, which is known to emit photons in pairs. The detection of one member of the pair activates the switch, which re-routes the other member into the storage loop. The stored photon is then known to be circulating in the loop, and can be switched out of the loop at a later time chosen by the user, providing a single photon for potential use in a variety of quantum information processing applications. To operate as a quantum memory for photonic qubits, a single-photon in an arbitrary initial polarization state is coherently stored in the loop, and coherently switched out of the loop when needed.

Abstract: Techniques are provided that use the quantum Zeno effect to implement practical devices that use single photons as the qubits for quantum information processing. In the quantum Zeno effect, a randomly-occurring event is suppressed by frequent measurements to determine whether the event has occurred. The same results can be obtained by using atoms or molecules or ions to react to the occurrence of the event. Techniques include directing one or more input qubits onto a device and applying a quantum Zeno effect in the device. The quantum Zeno effect is applied by consuming one or more photons in the device under conditions in which photons, that would otherwise be output by the device, do not represent a result of a particular quantum information processing operation. Devices implemented using the quantum Zeno effect can operate with low error rates without the need for high efficiency detectors and large number of ancilla.