Abstract: Methods and systems are provided to generate and use pairs of highly nondegenerate frequency-entangled photons for Hong-Ou-Mandel interferometric measurement of local or remote samples. The use of highly nondegenerate frequency-entangled photon pairs enables ultra-high spatial resolutions even in the presence of background noise, dispersive intermediate media and/or dispersive or multi-interface targets, and high probe photon losses. The use of highly nondegenerate, narrow-band, frequency-entangled photon pairs for interferometric measurement of distance also allows the interferometer to be calibrated more easily for the two (or more) discrete narrow bands of wavelengths represented by the photon pairs. The use of narrow-band nondegenerate frequency-entangled photon pairs also permits improved noise rejection and increased fidelity in coincidence detection.

Abstract: A system, and methods, for transmitting quantum states between a first node and a second node, or among more than two nodes. Each node is characterized by an instantaneous spatial position, and the instantaneous spatial position of the second node is repositionable within a frame of reference associated with the first node. A hovering drone is adapted either for running a quantum key transmission protocol in secure communication with the first node, and/or for running a quantum key reception protocol in secure communication with the second node. Either drone may serve as a relay of optical data between a base station and another drone. Secure communication among more than two nodes may be reconfigured.

Abstract: A system, and methods, for transmitting quantum states between a first node and a second node, or among more than two nodes. Each node is characterized by an instantaneous spatial position, and the instantaneous spatial position of the second node is repositionable within a frame of reference associated with the first node. A hovering drone is adapted either for running a quantum key transmission protocol in secure communication with the first node, and/or for running a quantum key reception protocol in secure communication with the second node. Either drone may serve as a relay of optical data between a base station and another drone. Secure communication among more than two nodes may be reconfigured.

Abstract: A system, and methods, for transmitting encrypted information as a quantum transmission between a first node and a second node, or among more than two nodes. Each node is characterized by an instantaneous spatial position, and the instantaneous spatial position of the second node is repositionable within a frame of reference associated with the first node. A hovering drone is adapted either for running a quantum key transmission protocol in secure communication with the first node, and/or for running a quantum key reception protocol in secure communication with the second node. Either drone may serve as a relay of optical data between a base station and another drone. Secure communication among more than two nodes may be reconfigured.

Abstract: A system, and methods, for transmitting encrypted information as a quantum transmission between a first node and a second node, or among more than two nodes. Each node is characterized by an instantaneous spatial position, and the instantaneous spatial position of the second node is repositionable within a frame of reference associated with the first node. A hovering drone is adapted either for running a quantum key transmission protocol in secure communication with the first node, and/or for running a quantum key reception protocol in secure communication with the second node. Either drone may serve as a relay of optical data between a base station and another drone. Secure communication among more than two nodes may be reconfigured.

Abstract: A method and apparatus for switching at least one wavelength component of an optical signal beam from a first state to a second state. The phase characterizing the optical signal component is incremented by interaction with one or more escort beams in a non-linear medium thereby switching the state of the optical signal component on the basis of its incremented phase. Multiple escort beams may also be employed to switch different wavelength components of the signal. The method may be employed to achieve high speed, and substantially transparent, switching of phase, intensity or polarization of a signal.

Abstract: A method and apparatus for switching at least one wavelength component of an optical signal beam from a first state to a second state. The phase characterizing the optical signal component is incremented by interaction with one or more escort beams in a non-linear medium thereby switching the state of the optical signal component on the basis of its incremented phase. Multiple escort beams may also be employed to switch different wavelength components of the signal. The method may be employed to achieve high speed, and substantially transparent, switching of phase, intensity or polarization of a signal.

Abstract: A quantum cryptography apparatus securely generates a key to be used for secure transmission between a sender and a receiver connected by an atmospheric transmission link. A first laser outputs a timing bright light pulse; other lasers output polarized optical data pulses after having been enabled by a random bit generator. Output optics transmit output light from the lasers that is received by receiving optics. A first beam splitter receives light from the receiving optics, where a received timing bright light pulse is directed to a delay circuit for establishing a timing window for receiving light from the lasers and where an optical data pulse from one of the lasers has a probability of being either transmitted by the beam splitter or reflected by the beam splitter. A first polarizer receives transmitted optical data pulses to output one data bit value and a second polarizer receives reflected optical data pulses to output a second data bit value.

Abstract: Utilizing the process of spontaneous parametric down-conversion in a novel crystal geometry, a source of polarization-entangled photon pairs has been provided that is more than ten times brighter, per unit of pump power, than previous sources, with another factor of 30 to 75 expected to be readily achievable. A high level of entanglement between photons emitted over a relatively large collection angle, and over a 10-nm bandwidth, is a characteristic of the invention. As a demonstration of the source capabilities, a 242-&sgr; violation of Bell's inequalities was attained in fewer than three minutes, and near-perfect photon correlations were achieved when the collection efficiency was reduced. In addition, both the degree of entanglement, and the purity of the state are readily tunable. The polarization entangled photon source can be utilized as a light source for the practice of quantum cryptography.

Abstract: Apparatus and method for secure communication between an earth station and spacecraft. A laser outputs single pulses that are split into preceding bright pulses and delayed attenuated pulses, and polarized. A Pockels cell changes the polarization of the polarized delayed attenuated pulses according to a string of random numbers, a first polarization representing a "1," and a second polarization representing a "0." At the receiving station, a beamsplitter randomly directs the preceding bright pulses and the polarized delayed attenuated pulses onto longer and shorter paths, both terminating in a beamsplitter which directs the preceding bright pulses and a first portion of the polarized delayed attenuated pulses to a first detector, and a second portion of the polarized delayed attenuated pulses to a second detector to generate a key for secure communication between the earth station and the spacecraft.