Abstract: The invention provides an apparatus and method for time delaying different polarization components of a signal relative to one another, comprising a polarization signal splitter which splits first and second polarization components of an input signal into a first component signal and a second component signal such that said first component signal propagates along a first path and the second component signal propagates along a second path, wherein said first component signal reaches a location relative to when said second component reaches said location at times differing by a delayed time, and use of the apparatus in a communication system. The apparatus may be used for quantum cryptography, to convert a sender's polarization-qubit signal into a signal appropriate for channels and receivers based on phase-encoded schemes.

Abstract: Systems and methods for forming a time-averaged line image having a relatively high amount of intensity uniformity along its length is disclosed. The method includes forming at an image plane a line image having a first amount of intensity non-uniformity in a long-axis direction and forming a secondary image that at least partially overlaps the primary image. The method also includes scanning the secondary image over at least a portion of the primary image and in the long-axis direction according to a scan profile to form a time-average modified line image having a second amount of intensity non-uniformity in the long-axis direction that is less than the first amount. For laser annealing a semiconductor wafer, the amount of line-image overlap for adjacent scans of a wafer scan path is substantially reduced, thereby increasing wafer throughput.

Abstract: A robust, quickly tunable narrow-linewidth entangled photon source system based on Spontaneous Parametric Down Conversion (SPDC) of the pump light in periodically polled LiNbO3 (PPLN) waveguides. The photon source provides narrow-linewidth, entangled output photons having a wavelength in the telecom C-Band wavelength. To tailor the output spectrum of the output photons, the PPLN waveguide is arranged between two end waveguides having LiNbO3-embedded Bragg gratings, thereby forming a tunable Fabry-Perot cavity. The resulting narrow output linewidth of the output photons makes the system desirable for use in a long-distance quantum key distribution (QKD) system.

Abstract: A quantum key distribution (QKD) cascaded network with loop-back capability is disclosed. The QKD system network includes a plurality of cascaded QKD relays each having two QKD stations Alice and Bob. Each QKD relay also includes an optical switch optically coupled to each QKD station in the relay, as well as to input ports of the relay. In a first position, the optical switch allows for communication between adjacent relays and in a second position allows for pass-through communication between the QKD relays that are adjacent the relay whose switch is in the first position.

Abstract: Systems and methods for quantum secret splitting based on non-orthogonal multi-particle states are disclosed. The method includes preparing at a sender (“Charlie”) two qubits each of which can be in one of two non-orthogonal states and distributing the qubits to respective parties Alice and Bob. The method also includes measuring at Alice the state of the qubit she receives by a projective measurement so that the measurement result is either 0 or 1, and at Bob measuring the state of the qubit he receives such that the measurement result is either 0, 1 or f, wherein f represents a failure by Bob to properly measure the qubit state. The method also includes communicating between Alice, Bob and Charlie the outcome of their respective measurements so as to deduce the state of the qubits sent to Alice and Bob.

Abstract: The invention is a sensitive measuring instrument, which is principally applied to quantum computation, especially to measurement of quantum bits consisting of superconducting micro and nano-structures. The state of a quantum bit is expressed as the voltage-time integral over a circuit component. Phase measurement is performed by measuring the capacitance of a single-electron transistor between the gate and ground.

Abstract: The invention includes systems for and methods of performing quantum computation. The method of quantum computation includes preparing a set of one or more qubits capable of storing quantum information in 2n possible states, wherein the number of qubits n?1. The qubit set is subject to a decoherence mechanism that could cause a loss of quantum information stored in some but not all of the qubit states. The method also includes determining, via a quantum measurement of the qubit system or just by analyzing the decoherence of the qubit states, which of the 2n states or their superposition is/are not susceptible to decoherence. The method further includes encoding and processing quantum information in one or more of the decoherence-free states by controlling qubit-qubit interactions or via an electromagnetic interaction with the set of qubits.

Abstract: An in-line night-day boresight with an adjustable wedge-prism assembly is disclosed. The adjustable wedge-prism assembly includes two opposing wedge prisms that are axially rotatable relative to each other. The assembly is arranged in the optical path between the night optics and the day optics. The adjustable wedge-prism assembly allows for compensation of image shift errors introduced by the night optics due to manufacturing errors in the night optics. This in turn allows for a cost-effective and easily aligned in-line night-day boresight.

Abstract: Systems and methods for compensating a QKD system for variations in temperature are disclosed. One of the methods includes identifying an optimum detector gating signal timing as a function of temperature for a single-photon detector (SPD) control board in one of the QKD stations. The detector gating signal timing versus temperature information is stored in a look-up table in a memory unit. The QKD system's temperature is monitored during operation and the timing of the detector gating signal is adjusted based on the operating temperature and the corresponding timing value adjustment in the look-up table. The result is a compensated detector gating timing signal provided to the SPD that yields an optimum number of photon counts even as the temperature of the QKD station varies.