Abstract: A system and method are provided for proactively buffering quantum key distribution (QKD) key material. The method includes monitoring key generation rates and surpluses at QKD devices at each node of a QKD link in a QKD network, retrieving surplus key material from the QKD devices at one or both nodes of the QKD link, and buffering the surplus key material in a local storage at one or both nodes in the QKD link. The surplus key material can be used to offset overhead introduced in securely relaying keys between non-adjacent demand pairs in the QKD network. The surplus key material can also be used to offset future transient decreases in key generation rates.

Abstract: A system and method are described for proactively performing key swaps among nodes in a quantum key distribution (QKD) network. The method includes determining a routing solution for nodes in the QKD network; making the routing solution available to the nodes in the QKD network; and initiating key swaps among the nodes in the QKD network according to the routing solution, prior to key requests being made within the QKD network. The method can also include continuously performing key swaps among the nodes in the QKD network according to the routing solution; detecting a change in capacity and/or a change in demand on one or more links within the QKD network; determining a new routing solution based on the detected change; and continuously preforming subsequent key swaps according to the new routing solution.

Abstract: A system and method are described for proactively performing key swaps among nodes in a quantum key distribution (QKD) network. The method includes determining a routing solution for nodes in the QKD network; making the routing solution available to the nodes in the QKD network; and initiating key swaps among the nodes in the QKD network according to the routing solution, prior to key requests being made within the QKD network. The method can also include continuously performing key swaps among the nodes in the QKD network according to the routing solution; detecting a change in capacity and/or a change in demand on one or more links within the QKD network; determining a new routing solution based on the detected change; and continuously preforming subsequent key swaps according to the new routing solution.

Abstract: A system and method are provided for proactively buffering quantum key distribution (QKD) key material. The method includes monitoring key generation rates and surpluses at QKD devices at each node of a QKD link in a QKD network, retrieving surplus key material from the QKD devices at one or both nodes of the QKD link, and buffering the surplus key material in a local storage at one or both nodes in the QKD link. The surplus key material can be used to offset overhead introduced in securely relaying keys between non-adjacent demand pairs in the QKD network. The surplus key material can also be used to offset future transient decreases in key generation rates.

Abstract: A method and system for quantum key distribution (QKD) between a first location and a second location through an intermediate location. The system and method include executing a quantum phase between each of the first and second locations and the intermediate location to determine a first location raw data string at the first location, a first-intermediate raw data string at the intermediate location, a second location raw data string at the second location, and a second-intermediate raw data string at the intermediate location, respectively; calculating, at the intermediate location, announcement data based on a function of the first and second-intermediate raw data strings; announcing, at the intermediary location, the announcement data over a classical channel; and deriving, at each of the first and second locations, a secret key based on the available data and on communications between the first and second locations via a classical channel.

Abstract: A method and system for quantum key distribution (QKD) between a first location and a second location through an intermediate location. The system and method include executing a quantum phase between each of the first and second locations and the intermediate location to determine a first location raw data string at the first location, a first-intermediate raw data string at the intermediate location, a second location raw data string at the second location, and a second-intermediate raw data string at the intermediate location, respectively; calculating, at the intermediate location, announcement data based on a function of the first and second-intermediate raw data strings; announcing, at the intermediary location, the announcement data over a classical channel; and deriving, at each of the first and second locations, a secret key based on the available data and on communications between the first and second locations via a classical channel.

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: Apparatus for and methods of random number generation are disclosed, wherein a detector receives a group of n light pulses having single-photon intensity levels. Each of the n light pulses has a probability of less than one to produce a successful detection event at its time of arrival at the detector, and the detector is adapted to detect only one of the n pulses in the group. This single detection per group is thus a discrete random event that occurs only during one of n fixed time slots. The random event occurring during one of n timeslots is converted into a corresponding random integer from 1 to n. A series of such random numbers is generated by using a plurality of groups of n light pulses.

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: In an apparatus and methods of random number generation, a detector (60) receives a plurality of groups of n light pulses (50), which an attenuator (40) typically dims to single-photon intensity levels. Each of the n light pulses has a probability less than one to produce a successful detection event at its time of arrival at the detector, but the detector detects only one of the n pulses per group. This single detection per group is thus a discrete random event. This detection even can occur only during one of n fixed timeslots during which a pulse may arrive at the detector. The method of the invention converts the random event at one of n timeslots into a random integer from 1 to n. The expected arrival time of the first pulse of the group becomes a timing reference with which to start a timer (90) and define the define the timeslots electronically.