Abstract: A method of scheduling encryption key delivery communication sessions in a satellite quantum key distribution system comprising a constellation of one or more satellites and a plurality of user ground stations comprises producing a list of user ground stations requiring encryption keys. For each satellite of the constellation of satellites, determining a region of the earths surface within which the satellite can carry out encryption key delivery communication sessions to user ground stations using a quantum optical communications link during a scheduling period. Obtaining a cloud cover map. Comparing the locations of the listed user ground stations, the determined regions of the earths surface for the constellation of satellites, and the cloud cover map, to identify listed user ground stations to which encryption key delivery can be carried out by the constellation of satellites during the scheduling period.

Abstract: A system and method including at a transmitter emitting N single-wavelength quantum beams from N faint photon sources; multiplexing the N single-wavelength quantum beams using a first wavelength division multiplexer (WDM) to produce a combined multi-wavelength quantum beam, wherein the combined multi-wavelength quantum beam comprises a series of interleaved single-photon events having different wavelengths, and has a repetition rate N times that of individual single-wavelength quantum beams; transmitting the combined multi-wavelength quantum beam to a receiver; and at the receiver: de-multiplexing the combined multi-wavelength quantum beam according to the wavelength using a second WDM to recover the N single-wavelength quantum beams; at N single photon detection units, receiving a respective quantum beam of the N quantum beams and detecting single photon events from the respective quantum beam, such that each single photon detection unit corresponds to a respective quantum beam and as such the respective wav

Abstract: A method for performing a key exchange between a first device, a second device, and an intermediary device, wherein the intermediary device: transmits to the first device a first secret symbol string over a first quantum channel and a first basis set over a first channel, transmits to the second device a second secret symbol string over a second quantum channel and a second basis set over a second channel, and generates a third symbol string by combining the first and second secret symbol strings and transmits data representative of the third symbol string to the second device, whereby the first and second devices perform a quantum key exchange and sifting based on the first and second secret symbol strings and first and second basis sets, and a fourth set of symbols is generated by the second device by combining the second secret symbols with the third symbol string.

Abstract: Method(s), system(s), apparatus are provided for storing one or more data item(s) in a quantum-safe (QS) network. The QS network comprising one or more QS server(s) and a repository for storing and accessing said data item(s). Each QS server comprising a hardware security module (HSM) for storing an identical set of quantum distributed (QD) keys. The identical set of QD keys having been distributed to each of said QS server(s) in a quantum-safe manner. The QS server(s) are configured to communicate securely with each other and the repository using one or more available QD keys from the identical set of QD keys. A QS server performs generating a quantum reference (QREF) locator based on input data associated with a data item for storage and an available QD key selected from the set of QD keys, and sending the QREF locator along with the data item encrypted with the available QD key to the repository for storage.

Abstract: Methods, apparatus, and systems are provided for performing a quantum key distribution (QKD) protocol between a first device, a second device, and an intermediary device. The intermediary device transmitting: a first secret symbol string over a first quantum channel to the first device; a first basis set over a first communication channel to the first device. The intermediary device; a second secret symbol string over a second quantum channel to the second device; a second basis set over a second communication channel to the second device. The intermediary device generating a third symbol string based on combining the first and second secret symbol strings and transmitting to the second device, via the second communication channel, data representative of the third symbol string.

Abstract: A method of operating a quantum key distribution (QKD) system including using a quantum random number generator (QRNG) to generate a random number string (RNS), and storing the RNS; providing the RNS to a first cryptographically secure pseudo-random number generator (CSPRNG) which uses random numbers of the RNS as seeds to generate respective first strings of pseudo-random numbers; using the first strings of pseudo-random numbers to encode photons or pulses transmitted by a transmitter of the QKD system; after a predetermined delay, providing the stored RNS to a second CSPRNG which uses random numbers of the RNS as seeds to generate respective second strings of pseudo-random numbers, the second CSPRNG identically configured to the first CSPRNG; using the second strings of pseudo-random numbers, together with information regarding encoded photons or pulses received by a receiver of the QKD system, to agree secure keys between the transmitter and the receiver.

Abstract: A method of aligning a quantum laser beam with a receiver, the method including: generating a quantum laser beam and a first classical, non-quantum, laser beam at a transmitter, the quantum laser beam and the first classical laser beam being substantially aligned in direction; transmitting the quantum laser beam and the first classical laser beam; and directing the quantum laser beam and first classical laser beam to a receiver; measuring the photon reception rate through the quantum laser beam at the receiver, and reporting the photon reception rate to the transmitter; at the transmitter, making a series of adjustments to the direction of the transmitted quantum laser beam and the first classical laser beam, and monitoring the reported photon reception rate; wherein, each of the series of adjustments is based, at least in part, on the effect of the preceding adjustment on the reported photon detection rate.

Abstract: A method for time synchronisation in a satellite based quantum key distribution system, by at a transmitter, emitting a first series of laser pulses (LP) encoded to form a quantum beam, emitting a second series of LP having a predetermined repeating pattern; at a receiver, receiving the first and second series of LP and determining reception times of pulses of the first and second series of LP; comparing the second series of LP to the predetermined pattern and determining the point at which the received second series of LP is most correlated to the predetermined pattern; determining a relationship fitting reception times of a plurality of the received pulses to emission times of corresponding ones of the second series of LP; and using the determined relationship to convert between reception times of the first series of LP and emission times of corresponding ones of the first series of LP.

Abstract: A method for performing a key exchange using a quantum key distribution protocol between a first device (D1), a second device (D2), and an intermediary device (ID), wherein: ID receives first symbol set (SS1) over first quantum channel (QC1) transmitted from D1 and sends first receiving basis information (RBI1) to D1 which withholds from ID first transmitting basis information (TBI1); ID transmits second symbol set (SS2) over second quantum channel (QC2) and second transmitting basis information (TBI2) to D2 which withholds from ID second receiving basis information (RBI2); ID generates first (IS1) and second intermediate symbol (IS2) sets based on valid SS1 and SS2; wherein ID generates third intermediate symbol (IS3) set by combining IS1 and IS2 and sends IS3 set to D1 and/or D2; wherein D1 and D2 exchange TBI1 and RBI2 and/or RBI1 and TBI2 to determine a final shared key based on SS1, SS2, and IS3 sets.

Abstract: A system for performing a key exchange using a quantum key distribution protocol between first, second, and intermediary devices, wherein the intermediary device: receives first symbol set over a first quantum channel transmitted from first device and sends first receiving basis information to first device, receives second symbol set over a second quantum channel transmitted from second device and sends second receiving basis information to second device, generates first and second intermediate sets of symbols based on received first and second sets of symbols, generates third intermediate symbol set by combining first and second intermediate sets and sends third intermediate set to first and/or second device, whereby first and second devices perform the key exchange by exchanging with themselves first and second transmitting basis information and/or first and second receiving basis information to determine a final shared key based on first, second, and third intermediate symbol sets.

Abstract: Method(s), system(s), apparatus are provided for storing one or more data item(s) in a quantum-safe (QS) network. The QS network comprising one or more QS server(s) and a repository for storing and accessing said data item(s). Each QS server comprising a hardware security module (HSM) for storing an identical set of quantum distributed (QD) keys. The identical set of QD keys having been distributed to each of said QS server(s) in a quantum-safe manner. The QS server(s) are configured to communicate securely with each other and the repository using one or more available QD keys from the identical set of QD keys. A QS server performs generating a quantum reference (QREF) locator based on input data associated with a data item for storage and an available QD key selected from the set of QD keys, and sending the QREF locator along with the data item encrypted with the available QD key to the repository for storage.

Abstract: Methods, apparatus, and systems are provided for performing a quantum key distribution (QKD) protocol between a first device, a second device, and an intermediary device. The intermediary device transmitting: a first secret symbol string over a first quantum channel to the first device; a first basis set over a first communication channel to the first device. The intermediary device; a second secret symbol string over a second quantum channel to the second device; a second basis set over a second communication channel to the second device. The intermediary device generating a third symbol string based on combining the first and second secret symbol strings and transmitting to the second device, via the second communication channel, data representative of the third symbol string.

Abstract: A method of scheduling and managing key data in a satellite quantum key distribution system comprising a constellation of one or more satellites and a plurality of user ground stations.