2159results about "Photonic quantum communication" patented technology

Methods and apparatus for use in quantum key distribution (QKD) are described. A quantum QKD signal is generated at a source and transmitted through a fibre optic network to an endpoint, a key being agreed with communication over a classical QKD channel. The classical QKD channel contains additional information relevant to a network over which keys are distributed, and may be processed at nodes intermediate between the source and the endpoint.

A source and / or method of generating quantum-correlated and / or entangled photon pairs using parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550 nm fiber-optic communication band and detected by a detection system including InGaAs / InP avalanche photodiodes operating in a gated Geiger mode. A generation rate>103 pairs / s is observed, a rate limited only by available detection electronics. The nonclassical nature of the photon correlations in the pairs is demonstrated. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks. The detection system also provides high rate of photon counting with negligible after pulsing and associated high quantum efficiency and also low dark count rate.

A system for communicating data comprising sender and receiver subsystems; at least one data input; at least one entangled photon source; first photons of the pairs of entangled photons outputted by the at least one photon source being processed by one of the sender or receiver subsystem; second photons of the pairs of entangled photons being processed by the other of the sender or receiver subsystem; a photonic element configured to receive the first photons of the pairs of entangled photons and enable interference therebetween; at least one absorber configured to absorb the first photons after passage through the beam splitter, the absorbance of the first photons operating to transfer the properties of the entanglement to the second photons of the pairs of entangled photons; and a Bell state measurement element operatively associated with the receiver subsystem configured to measure the second photons of the pairs of entangled photons.

An electro-optical system for exchanging quantum information between optical qubits and including a superconductive microwave cavity; an electro-optical material: a superconductive qubit circuit formed on the electro-optical material including a superconductive qubit; a dipole antenna, formed on the electro-optical material for directly coupling the superconductive qubit to the superconductive microwave cavity; an optical input for receiving input optical photons; a microwave input for receiving input microwave photons; and an optical output for outputting modulated optical photons, wherein a frequency and a phase of the optical photon is modulated with a state of the superconducting qubit by the dipole antenna.

QKD system networks (50, 200, 300) and methods of communicating between end-users (P1, P2) over same are disclosed. An example QKD system network (50) includes a first QKD station (A1) and a second QKD station (A2) with a relay station (58) in between. The relay station includes a single third QKD station (B) and an optical switch (55). The optical switch allows the third QKD station to alternately communicate with the first and second QKD stations so as to establish a common key between the first and second QKD stations. The end-users are coupled to respective QKD stations A1 and A2. A secret key (S) is shared between P1 and P2 by QKD station B being able to independently form keys with A1 and A2. This basic system, represented as P1-A1-B-A2-P2, can be expanded into more complex linear networks, such as P1-A1-B1-A2-B2-P2 with B1 and A2 making up the relays. The basic QKD system network can also be expanded into multi-dimensions.

A communication system uses quantum cryptography for the secure distribution of a key. A single-photon signal is phase-modulated and transmitted over a pair of time-multiplexed transmission paths. With each original single-photon signal in a given one of the transmission paths, a duplicate signal is transmitted. The duplicate is identically modulated and orthogonally polarized. At the receiver, the outputs of the two paths are combined interferometrically. A single polarization-insensitive measurement is derived from the combined contributions of the orthogonally polarized signals.

Methods and systems for a photonic interposer are disclosed and may include receiving one or more continuous wave (CW) optical signals in a silicon photonic interposer from an external optical source, either from an optical source assembly or from optical fibers coupled to the silicon photonic interposer. The received CW optical signals may be processed based on electrical signals received from the electronics die. The modulated optical signals may be received in the silicon photonic interposer from optical fibers coupled to the silicon photonic interposer. Electrical signals may be generated in the silicon photonic interposer based on the received modulated optical signals, and may then be communicated to the electronics die via copper pillars. Optical signals may be communicated into and / or out of the silicon photonic interposer utilizing grating couplers. The electronics die may comprise one or more of: a processor core, a switch core, or router.

An entangled links mechanism to establish and maintain bipartite temporal intimacy between pairs of computers, using an idempotent, reversible token method which presents no observable external “change” until a communication of information needs to occur between the computers, and which maintains the potential for “bounded (or unbounded) reversibility” in case the intended information dispatched by a source computational entity is not captured or properly accepted by a destination computational entity. The mechanism enables distributed computers in a network to remain continuously aware of each other's presence; to communicate on a logically nearest neighbor basis in a secure and reliable manner in which packets passed over these links do not conflict with normal traffic or cause the available resources of the link to be exceeded; and that atomicity, consistency, isolation, and “reversible durability” may be maintained for transactions when perturbations occur.

A system includes an optical network unit and a head-end or central office connected to a multi-drop optical network. The optical network unit transmits dim optical pulses via the multi-drop optical network using quantum cryptographic mechanisms to distribute encryption key symbols, where the dim optical pulses include one of single-photon optical pulses or weak attenuated optical pulses. The head-end or central office detects the dim optical pulses from the optical network unit, derives the encryption key symbols from the detected dim optical pulses, and encrypts data transmitted to the optical network unit using the encryption key symbols.

PCT No. PCT / GB94 / 02067 Sec. 371 Date Apr. 10, 1996 Sec. 102(e) Date Apr. 10, 1996 PCT Filed Sep. 23, 1994 PCT Pub. No. WO95 / 10907 PCT Pub. Date Apr. 20, 1995A cryptographic receiver (10) includes photon detectors (52, 54, 56, 58) arranged to detect photons arriving from filters (22) and (24). A fiber coupler (14) randomly distributes each received photon (16) from an optical fiber toone of two photon channels (18, 20). The filters (22, 24) are each unbalanced Mach-Zehner interferometers with a phase modulator (34, 44) in one arm (28, 38). The filters (22, 24) impose non-orthogonal measurement bases on photons within the respective channels (18, 20). A signal processor (60) derives a cryptographic key-code by analysis of signals received from the photon detectors (52, 54, 46, 58).

The present invention is directed to realize a stable and highly-efficient quantum communication without being influenced by the jitter of the heralding signal. In regard to the quantum encryption transmitting apparatus 200, the pulse-driven heralded single-photon source 201 generates a photon pair, outputs one photon of the photon pair, and outputs the other photon of the photon pair as a heralding signal. The timing adjuster 202 synchronizes the heralding signal with a clock signal for pulse driving the pulse-driven heralded single-photon source 201, and outputs as a trigger signal. The quantum communication modulating unit 203 implements the signal modulation to a quantum signal, in timing with the trigger signal, and transmits the quantum signal to the quantum encryption receiving apparatus 300 via the quantum communication path 101. The heralding signal transmitting unit 205 transmits the heralding signal to the quantum encryption receiving apparatus 300 via the heralding signal communication path 102. The clock signal transmitting unit 206 transmits the clock signal to the quantum encryption receiving apparatus 300 via the clock communication path 103.

A method of data compression and transmission include splitting a wave function representative of an input data set into an arbitrarily oriented elliptical polarization state and a comparator wave function state, the comparator wave function state being transmitted to a detector. A quantum Fourier transform is performed on the arbitrarily oriented elliptical polarization state to yield a quantum computational product. A quantum Hadamard transform is performed on the quantum computational product to yield one of two possible quantum particle outputs. The input data set is reconstructed based upon the coincident arrival of the comparator wave function state and one of the two quantum particle outputs. A method is performed on either a quantum computer or a digital computer. An optical bench with appropriate electronics is particularly well suited to function as a quantum computer for the compression and transmission of data corresponding to sound.

Systems and methods for orbital angular momentum (OAM)-based multidimensional wireless communication. The OAM-based multidimensional wireless communication is preformed with a transmitter for generating an RF modulated signal carrying a data sequence. Further included is an OAM antenna array including OAM antenna elements, each of which includes an azimuthal phase shifter and an antenna element. The azimuthal phase shifter shifts an azimuthal phase term of a wavefront generated by the antenna element such that the OAM antenna element imposes the multidimensional modulated signal on a pre-determined OAM mode of a carrier signal corresponding to the azimuthal phase term.

A system and a method for quantum key distribution between a transmitter and a receiver over wavelength division multiplexing (WDM) link are disclosed. The method includes providing one or more quantum channels and one or more conventional channels over the WDM link; assigning a different wavelength to each of the one or more quantum channels and each of the one or more conventional channels; transmitting single photon signals on each of the one or more quantum channels; and transmitting data on each of the one or more conventional channels. The data comprises either conventional data or trigger signals for synchronizing the transmission of the single photon signals on the quantum channels. All channels have wavelengths around 1550 nm. The WDM link can be a 3-channel WDM link comprising two quantum channels for transmitting single photon signals and one conventional channel for transmitting conventional data or triggering signals.

A QKD system having QKD link redundancy between two sites, with the system having only one QKD station at each site, and with two or more QKD links operably coupled to the QKD stations. The QKD stations have respective optical switches that are optically coupled to both QKD links and that are controlled by respective controllers in each of the QKD stations. If one of the QKD links fails or has trouble transmitting optical signals, the QKD switches are switched so that the optical path between the QKD stations uses the remaining QKD link. This arrangement requires only two QKD stations rather than the four QKD stations as presently taught in the prior art.

A qubit generating unit 40 generates a qubit having a predetermined quantum state. A qubit encoding unit 70 performs quantum encoding of the generated qubit. A first pseudo-random number generating unit 60 generates a first pseudo-random number from secretly shared information 3 which has been secretly shared with the quantum receiving device 200 in advance. A quantum modulator 80 performs quantum modulation of the qubit on which quantum encoding has been performed based on the first pseudo-random number and sends the modulated qubit to the quantum receiving device 200. A second pseudo-random number generating unit 220 generates a second pseudo-random number from secretly shared information 21 which has been secretly shared with the above quantum sending device 100 in advance synchronously with generation of the above first pseudo-random number. A qubit demodulator 230 performs quantum demodulation of the qubit which has been received from the quantum demodulator 80 based on the second pseudo-random number.

A system and a method for quantum key distribution over a multi-user wavelength division multiplexing (WDM) network are disclosed. The system comprises a tunable or multi-wavelength transmitter; a plurality of receivers, each assigned a receiving-wavelength; and a multi-user WDM network linking the transmitter to the receivers. The transmitter can select a receiver among the receivers to be communicated therewith and transmit quantum signals to the selected receiver over the WDM network. The quantum signals are at a wavelength equal to a receiving-wavelength of the receiver. Therefore the WDM network allows quantum signals to be communicated between the transmitter and the receivers by wavelength routing.

Systems and methods are described in which both a quantum key distribution (QKD) transmitter and QKD receiver may keep both of their two-path interferometers stable, with regard to path length drift, relative to an internal reference laser are described. Systems and methods are also proposed whereby the transmitter interferometer may have only a single path (e.g., Sagnac interferometers). The systems and methods described herein may greatly improve the performance of quantum cryptographic transceivers that may make use of these systems and methods.

The invention provides a photon method and system for realizing microwave down-conversion and phase shift by using integrated devices, and belongs to the field of microwave photonics. Firstly, opticalcarriers generated by a laser are input to a double-parallel Mach-Zehnder modulator after passing through a polarization controller, a radio frequency signal is modulated by an upper arm sub-modulator, and carrier suppression double-sideband modulation is realized by DC bias; a local oscillator signal is modulated by a lower arm sub-modulator, and the carrier suppression double-sideband modulation is realized by the DC bias; the DC bias of a main intensity modulator is used for changing the phase difference between the radio frequency optical signal and the local oscillator optical signal. A-1 order optical sideband is filtered from an output carrier suppression double-sideband modulation optical signal by an optical bandpass filter, a +1 order optical sideband is retained, and the useless optical sideband is suppressed below the noise floor. Then, power amplification is performed on the optical signal to compensate the insertion loss of modulator and the filter. At last, a down-conversion signal subjected to phase shift is obtained by performing beat frequency by using a photodetector. A very pure frequency spectrum signal is output, and the performance of an integrated functionlink of down-conversion and phase shift is improved.

A quantum cryptographic protocol is proposed, which uses two-mode coherent states and an M-ary modulation format determined in part by an expanded secret key. The encrypted signal is optically amplifiable, resulting in a polarization independent system that is compatible with the existing WDM communications infrastructure.

One embodiment provide a system and method for detecting eavesdropping while establishing secure communication between a local node and a remote node. During operation, the local node generates a random key and a regular optical signal based on the random key. The local node also generates a quantum optical signal based on a control sequence and a set of quantum state bases, and multiplexes the regular optical signal and the quantum optical signal to produce a hybrid optical signal. The local node transmits the hybrid optical signal to the remote node, sends information associated with the control sequence and information associated with the set of quantum state bases to the remote node, and receives an eavesdropping-detection result from the remote node based on measurement of the quantum optical signal, the information associated with the control sequence, and the information associated with the set of quantum state bases.

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.

A system comprises a source of entangled photon pairs. The source is to place a signal photon and an idler photon in individual unknown quantum states but in a known entangled quantum state. One or more transmission channels are connected to the source. Each of the one or more transmission channels transmits one of the signal photon or the idler photon. Each of the one or more transmission channels is to substantially balance an instantaneous transmission loss with an instantaneous transmission gain distributed over a transmission distance. Analysis interferometers are configured to receive a corresponding one of the signal photon or the idler photon. Each of the one or more analysis interferometers is to perform a basis measurement on one of the signal photon or the idler photon. Single-photon detectors detect one of the signal photon or the idler photon.

The invention discloses a quantum communication ATP (array transform processor) precise tracking system with an optical axis self-calibrating function and a calibrating method thereof, aiming at overcoming the problem that the center of the quantum light emitting optical axis and the visual field center of the precise tracking camera are inconsistent owning to emitting vibration, on-track weight loss, thermal gradient and the like. The precise tracking system consisting of a pyramidal prism, a quick directing mirror, a CMOS (complementary metal-oxide-semiconductor) camera, a quantum emitting module, a color-separating piece and the like is adopted, and a path of strong light of other wavelength is introduced in the quantum emitting module by an optical fiber combiner and is used as a self-calibrating light. Before the instrument works, the self-calibrating light is introduced in the camera to form images by a track selector; the position of the mass center of light spot is calculated and is used as the visual axis center during tracking external target. The established inter-satellite or satellite-ground optical link can lead the ATP system to capture and precisely track the target at the receiving end and to exactly send the quantum signal to the receiving end along the optical link simultaneously, thus ensuring to successfully realize the spatial scale quantum communication.