A method of correcting gravity-induced error in quantum cryptography system, which is capable of improving accuracy when an optical cable is not installed and photons are transmitted through an artificial satellite, is disclosed. The method performed by an electronic device, comprises receiving a distance (r) to a satellite that receives polarized photon from a sender and transmits the polarized photon to a receiver, receiving an angular momentum per unit mass of the satellite (l.sub.obs), and calculating a rotation amount of the polarized photon, which is induced by a warp of space due to gravity by using the distance to the satellite and the angular momentum per unit mass of the satellite (l.sub.obs). The rotation 2Θ of the polarized photon is calculated by the following equation, $\sin \Theta \left(r\right)\cong -\frac{l_{\mathrm{obs}}}{\sqrt{{\mathrm{rr}}_s}}\sqrt{1-\frac{r_s}{r}},$
wherein ‘r.sub.s’ is the Schwarzschild radius of the Earth.

A system includes a switch of an electric power distribution system, the switch being configured to receive data and to transmit data, and the system includes a controller configured to communicatively couple to the switch. The controller is configured to create a software defined network by instructing the switch to transmit data to a location, and the controller is configured to generate a set of keys and to provide the set of keys to the switch to enable the switch to communicate data via a Media Access Security (MACsec) communication link, a MACsec key agreement (MKA) connectivity association, or both.

A device and method for quantum key distribution (QKD). The QKD center includes an authentication key sharing unit for sharing authentication keys with QKD client devices; a quantum key generation unit for generating a sifted key for each of the QKD client devices using a quantum slate; an error correction unit for generating output bit strings by correcting errors of the sifted keys; and a bit string operation unit for calculating an encryption bit string by performing a cryptographic operation on the authentication keys, the distribution output bit strings and output bit strings received from the QKD client devices. The present invention improves security by preventing the QKD center from being aware of keys shared among users.

Methods and apparatus for distribution of keys are disclosed. An optical signal for carrying encoded information in accordance with a quantum key distribution scheme is generated. The generated optical signal has a wavelength which is changed to another wavelength prior to transmission of the optical signal. The optical signal carrying the encoded information and having the changed wavelength is received, where after decoding of the information takes place by means of detector apparatus operating in the changed wavelength.

A method for compressing a quantum state vector includes: aggregating a group of several neighboring states of the vector into a cluster of states of the vector, a parameter representative of the probability of this cluster being associated with it and corresponding to the sum of the probabilities of the aggregated neighboring states in this cluster, the probability of each aggregated neighboring state being below a given aggregation threshold, and/or the sum of the probabilities of the aggregated neighboring states in a cluster being below another given aggregation threshold; and preserving a state of the vector not aggregated in a cluster, the parameter representative of its probability remaining unchanged. The method includes several steps of aggregating several distinct groups of several neighboring states of the vector, respectively into several clusters of states of the vector, and/or an aggregation step and a preservation step.

A passive continuous-variable quantum key distribution scheme, where Alice splits the output of a thermal source into two spatial modes, measures one locally and transmits the other mode to Bob after applying attenuation. A secure key can be established based on measurements of the two modes without the use of a random number generator or an optical modulator.

A large-scale tunable-coupling ring array includes an input waveguide coupled to multiple ring resonators, each of which has a distinct resonant wavelength. The collective effect of these multiple ring resonators is to impart a distinct time delay to a distinct wavelength component (or frequency component) in an input signal, thereby carrying out quantum scrambling of the input signal. The scrambled signal is received by a receiver also using a large-scale tunable-coupling ring array. This receiver-end ring resonator array recovers the input signal by imparting a compensatory time delay to each wavelength component. Each ring resonator can be coupled to the input waveguide via a corresponding Mach Zehnder interferometer (MZI). The MZI includes a phase shifter on at least one of its arms to increase the tunability of the ring array.

Instantaneous key invalidation in response to a detected eavesdropper. A quantum computing system that includes a plurality of qubits and a quantum channel uses a quantum key distribution protocol to generate a key. The quantum computing system determines that an eavesdropper has eavesdropped on the quantum channel. In response to determining that the eavesdropper has eavesdropped on the quantum channel, the quantum computing system sends a key-revocation message to a designated destination.

Systems, apparatuses, methods, and computer program products are disclosed for quantum entanglement random number generation (QERNG). An example method for QERNG includes, among other operations, generating a quantum entanglement random number based on a subset of a first set of entangled quantum particles associated with a first computing device. Each entangled quantum particle in the first set of entangled quantum particles may be entangled with a respective entangled quantum particle in a second set of entangled quantum particles associated with a second computing device. In some instances, the example method may further include generating a cryptographic key based on the quantum entanglement random number, encrypting an electronic communication based on the cryptographic key, and transmitting the encrypted electronic communication to the second computing device.

The present application relates to a method for securely transmitting a sequence of quantum states between a first participant C.sub.i and a second participant C.sub.j among a plurality of N participants, and to a device implementing said secure transmission method.