Abstract: A quantum-cryptographic communication system for quantum-cryptographic communication in an optical network, including a transmitter for transmitting a packet signal having a light pulse train representing an address and a single photon pulse train for quantum cryptography, and a router including a header analyzer for extracting the address information from the light pulse train of the packet signal and a gate switch for selecting one of the optical fibers. The router routes the packet signal by selecting an optical fiber used for the next transmission path according to the extracted address information by the header analyzer and by switching the path to the selected optical fiber by the gate switch.

Abstract: A system for and method of processing complex signals encoded into quantum states is presented. According to an embodiment of the invention, polarized components of a pump laser beam are separated and respectively modulated with first and second signals. The modulated polarized components are directed to adjacent non-linear crystals with optical axes aligned at right angles to each-other. Information regarding at least one of the first and second signals is then derived from measurements of coincidence events.

Abstract: Apparatus and method for a secure communication network using AlphaEta quantum encryption is provided. A polarization insensitive optical receiver based on a 90 degrees hybrid coupler is used for the detection and digitization of optically encrypted signals. Once digitized, such signals can be decrypted, stored, or re-transmitted over arbitrary media such as using RF wireless means. Alternatively, the signal can be generated directly for transmission over RF wireless nodes. The system may include nodes for retransmitting the signal without decrypting it, allowing for secure communication among specific users.

Abstract: Systems and methods for quantum secret splitting based on non-orthogonal multi-particle states are disclosed. The method includes preparing at a sender (“Charlie”) two qubits each of which can be in one of two non-orthogonal states and distributing the qubits to respective parties Alice and Bob. The method also includes measuring at Alice the state of the qubit she receives by a projective measurement so that the measurement result is either 0 or 1, and at Bob measuring the state of the qubit he receives such that the measurement result is either 0, 1 or f, wherein f represents a failure by Bob to properly measure the qubit state. The method also includes communicating between Alice, Bob and Charlie the outcome of their respective measurements so as to deduce the state of the qubits sent to Alice and Bob.

Abstract: A high data rate optical signal is inverse multiplexed into a multitude of lower-rate tributaries, each of which is coded by its unique OCDM code, and the combined coded tributaries are injected into a common phase scrambler. Coherent summation of these optically encoded tributaries pass through a shared phase or phase and frequency scrambler before exiting the secure location. The setting of the scrambler acts as the key. The authorized recipient with the correct key retrieves the ones and zeros of the several decoded signals.

Abstract: Embodiments of the invention relate to systems and methods for securing data transmission in networks. Embodiments of the invention further relate to encryption methods that dynamically adjust during the course of data transmission. Further, the encryption methods can adapt dynamically without user intervention. In one embodiment, an encryption scheme can be established, controlled, and monitored via out-of-band communication between transceiver modules.

Abstract: Substantially identical numerical sequences known only to stations A and B are generated in a manner not subject to duplication by an eavesdropper and not subject to cryptanalytic attack because they are not derived using a mathematical function (such, as for example, factoring). The sequences are independently derived utilizing a physical phenomena that can only be “measured” precisely the same at stations A and B. Signals are simultaneously transmitted from each station toward the other through a communication channel having a characteristic physical property capable of modifying the signals in a non-deterministic way, such as causing a phase shift. Each signal is “reflected” by the opposite station back toward its station of origin. The effect of the communication channel is “measured” by comparing original and reflected signals. Measured differences are quantized and expressed as numbers.

Abstract: In a method for the production of a single photon source with a given operational performance, the given operational performance for the individual photon source may be fixed by a directed setting of the fine structure gap of the excitonic energy level for at least one quantum dot. The at least one quantum dot is produced with a quantum dot size corresponding to the fine structure gap for setting.

Abstract: A system and method is provided for identifying fraudulent data in an optical data transmission. The system and method includes scrambling an encoded data signal using dynamically changing scramble code; transmitting the scrambled encoded data signal over a network; descrambling the scrambled encoded data signal using a descramble code corresponding to a compliment of the dynamically changing scramble code; analyzing the descrambled encoded data signal to search for a region of low error between descrambled data and noise; notifying of a possible spoofing attempt when a region of low error is not found; and decoding the descrambled encoded data signal using a compliment of phase codes originally used for encoding the encoded data signal in order to generate a decoded signal to retrieve a desired data signal when a region of low error is found.

Abstract: A photon emitter including a photon generator configured to generate photons having a first polarization state or a second polarization state, the first polarization state being orthogonal to the second polarization state; and a time delay device which delays photons having the second polarization state with respect to those having the first polarization state.

Abstract: An integrated circuit and method are provided for preventing reverse engineering by monitoring light emissions emitted from transistors and such electrically active devices in the integrated circuit. The method prevents, in an integrated circuit, a pattern of light emitted from at least one active device in the integrated circuit from being detected external to the integrated circuit by randomizing a pattern of light emitted from the at least one active device in an integrated circuit and that is emitted external to the integrated circuit. The pattern of light emitted from the at least one active device in the integrated circuit and that is emitted external to the integrated circuit can be randomized by randomizing a clock signal applied to a clocked circuit comprising the at least one active device in the integrated circuit.

Abstract: In one embodiment, messages are encrypted with encrypted transformations that commute with one another. In another embodiment, a message is divided into message segments, and with each encrypted message segment one or more encrypted keys are sent. The encrypted keys may be used to decrypt a message segment that is sent at another time, such as the next message segment to be sent. In another embodiment, a sender encrypts a message with a first encryption, which may be unknown to the receiver. Then a receiver encrypts the message with a second encryption. Next the sender removes the first encryption, thereby allowing the receiver to reconstitute the original message by removing the second encryption. In another embodiment, a sender encrypts a message with a first encryption and a signature. Then a receiver encrypts the message with a second encryption.

Abstract: Differential phase shift (DPS) quantum key distribution (QKD) is provided, where the average number of photons per transmitted pulse is predetermined such that the secure key generation rate is maximal or nearly maximal, given other system parameters. These parameters include detector quantum efficiency, channel transmittance and pulse spacing (or clock rate). Additional system parameters that can optionally be included in the optimization include baseline error rate, sifted key error rate, detector dead time, detector dark count rate, and error correction algorithm performance factor. The security analysis leading to these results is based on consideration of a hybrid beam splitter and intercept-resend attack.

Abstract: 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.

Abstract: Apparatus and methods for establishing a secret key to encrypt and share data using quantum signals represented by an equiangular spherical code and using classical signals in authenticating the key.

Abstract: The invention is directed toward a variable spectral phase encoder. The variable spectral phase encoder includes a plurality of switches and at least one encoder. The encoder is coupled between a first switch and second switch among the plurality of switches. The first switch selectively routes an optical signal to some combination of fixed encoders such that their collective product applies one of the Hadamard sequences to the optical signal.

Abstract: A data encryption-decryption method includes the steps of receiving a data byte N and performing a triple-churning operation on byte N to obtain an encrypted byte N. Preferably, the triple-churning operation includes performing a first churning operation to obtain a first churned output, bit-wise XORing the first churned output with two values to obtain a first XOR result, performing a second churning operation on the first XOR result to obtain a second churned output, bit-wise XORing the second churned output with two values to obtain a second XOR result, and performing a third churning operation on the second XOR result to obtain encrypted byte N.

Abstract: Provided are an apparatus for receiving a quantum cryptographic key and an apparatus for transmitting and receiving a quantum cryptographic key at high speed without polarization drift of an optical pulse signal and phase drift of an interferometer. The apparatus for receiving a quantum key includes: a polarization-insensitive optical phase modulator parts for receiving an optical pulse signal, and modulating and outputting a phase of the optical pulse signal without being affected by the polarization state of the optical pulse signal; an asymmetric Mach-Zehnder interferometer for causing interference in and outputting the optical pulse signal received from the polarization-insensitive optical phase modulator parts; and a photon detectors for detecting the optical pulse signal received from the asymmetric Mach-Zehnder interferometer.

Abstract: Encoding digital data intended for transmission by a particle flow of single particles, includes: encoding digital data on a parameter x of said particle flow, wherein the parameter x has a conjugated parameter y of said particle flow; and ensuring that said parameter x and said conjugated parameter y are in a minimum state (?x. ?y=1).

Abstract: An apparatus to implement role based access control which reduces administrative expenses associated with managing access in accordance with policies and roles. The apparatus includes a memory storing a first role based access control condition associated with an action and a subsystem executing an enforcement entity and a decision entity. In various forms, the two entities are independent entities. The enforcement entity receives a request for the action from a requestor with a role. Additionally, the enforcement entity communicates the role and the request to the decision entity for the decision entity's decision of whether the role satisfies the first condition. The decision entity then communicates the decision to the enforcement entity. Accordingly, the enforcement entity allows or denies the requester the action based on the decision made by the decision entity.

Abstract: 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.

Abstract: An optical network, having an optical communication link and first and second routers. The first router receives and classifies data, then forms a data burst based on destination. The first router sends an encrypted header and the data burst via the optical link. The second router, at least one hop from the first router, receives, decrypts and authenticates the header. Then, the second router extracts data burst information from the header and determines whether the address of the second router is the destination address for the data burst. If so, the second router receives the data burst and sends data to an appropriate line interface. If not, the second router selects and reserves a wavelength on a second optical link for the data burst. The second router selects an encryption key for the header, encrypts and sends the header, and then routes the data burst to the selected wavelength.

Abstract: QKD receiving apparatus is provided with an alignment-correction system for correcting misalignment of a quantum signal received at an optical port of the apparatus relative to a quantum-signal detector of the receiving apparatus. The alignment-correction system comprises a misalignment measuring subsystem for making multiple different misalignment measures, and a misalignment compensation subsystem for adjusting the relative alignment of the quantum signal and quantum-signal detector in dependence on the misalignment measures made. The misalignment measuring subsystem comprises an alignment-beam source, an alignment-beam detector arrangement, and optical components for guiding an alignment beam from the alignment-beam source to the optical port, and for guiding the alignment beam, after external retro-reflection at a cooperating QKD transmitting apparatus from the optical port to the alignment-beam detector arrangement.

Abstract: A quantum cryptographic key distribution (QKD) endpoint (405) includes a QKD receiver and a feedback system (1600). The QKD receiver receives symbols transmitted over a QKD path. The feedback system (1600) controls a length of the QKD path based on the received symbols.

Abstract: A method for enhancing the security of a quantum key distribution (QKD) system having QKD stations Alice and Bob. The method includes encrypting key bits generated by a true random number generator (TRNG) and sent to a polarization or phase modulator to encode weak optical pulses as qubits to be shared between Alice and Bob. Key bit encryption is achieved by using a shared password and a stream cipher. Bob obtains at least a subset of the original key bits used by Alice by utilizing the same stream cipher and the shared password.

Abstract: The invention relates to a node device (21) for a network (20) comprising quantum cryptographic connections (1) provided with quantum channels (4) and public channels (5), comprising quantum optics means (11) for connecting to the respective quantum channels, for generating secrets or keys by means of quantum cryptography, comprising means (13) for managing symmetrical secrets or keys, cryptography means (14) for generating cryptograms, and driver means (15) connected thereto for transmission via a public channel, wherein the means (15) for managing symmetrical secrets or keys and the cryptography and driver means (14; 15) are combined in a common node module (24) as central components (13, 14, 15) for a plurality of quantum channel connections, while the quantum optics means (11) are provided separately in decentral modules (23) for the plurality of quantum channel connections.

Abstract: A sender sends original random-number data to a receiver through a quantum channel. The receiver generates a raw key from information received through the quantum channel and notifies the received information to the sender. The sender performs received-bit comparison and basis reconciliation based on the received information and provisionally shares a sifted key with the receiver. The receiver sends part of its version of the sifted key to the sender, by which an error rate is calculated. The calculated error rate is compared with a predetermined threshold value for bit position synchronization determination. When the calculated error rate is larger, the sender notifies the receiver that bit position synchronization is not established. The receiver reassigns bit numbers to the sifted key, and received-bit comparison and basis reconciliation are performed again. This procedure is repeated until the calculated error rate becomes smaller than the threshold value.

Abstract: In a system where a quantum channel and a classical channel are multiplexed on a single optical transmission line and information is transmitted from a transmitter to a receiver through the quantum channel, the classical channel is inhibited from affecting the quantum channel. To this end, the transmission characteristics of a transmitter-side wavelength multiplexer/demultiplexer for the classical channel, the transmission characteristics of a receiver-side wavelength multiplexer/demultiplexer for the quantum channel, and the optical power of a light source for the classical channel are designed so that crosstalk light due to spontaneous emission light and crosstalk light due to nonlinear optical effects can be suppressed, and the classical channel does not affect the quantum channel.

Abstract: In order to create a highly-secured common key while a data error on a transmission path is corrected by an error correction code having remarkably high characteristics, in a quantum key distribution method of the invention, at first a communication apparatus on a reception side corrects the data error of reception data by a deterministic, stable-characteristics parity check matrix for a “Irregular-LDPC code.” The communication apparatus on the reception side and a communication apparatus on a transmission side discard a part of pieces of the common information according to public error correction information.

Abstract: One embodiment provides a system for decrypting data frames in an Ethernet passive optical network (EPON). During operation, the system maintains a local cipher counter at a local node, and receives from a remote node a data frame which is encrypted based on a remote input block and a session key. The remote input block is constructed based on the remote cipher counter and a remote block counter. The system updates the local cipher counter based on a received field located in a preamble of the data frame, truncates the local cipher counter by discarding a number of least significant bits, and constructs for the received data frame a local input block based on the truncated local cipher counter, the received field, and a local block counter. The system then decrypts the data frame based on the local input block and the session key.

Abstract: A two-way actively stabilized QKD system that utilizes control signals and quantum signals is disclosed. Because the quantum signals do not traverse the same optical path through the system, signal collisions in the phase modulator are avoided. This allows the system to have a higher transmission rate than a two-way system in which the quantum signals traverse the same optical path. Also, the active stabilization process, which is based on maintaining a fixed relationship between an intensity ratio of interfered control signals, is greatly simplified by having the interferometer loops located all in one QKD station.

Abstract: An apparatus and method for implementing a quantum cryptography system that requires fewer random bits. The emitter divides the key in blocks of bits. Instead of changing the basis for each bit of key sent by the emitter, the same basis is used for all the bits within a block. By doing this, the rate of random bits of information necessary for the implementation of a secure quantum cryptography link is reduced.

Abstract: In a cryptographic key distribution system by the phase modulation using a single photon state or a faint LD light, there is required an interferometer independent on polarization and stabilized against thermal fluctuations in order to make a transmission distance longer. Cryptographic key distribution systems are generally low in cryptographic-key-generating efficiency, and an improvement in the efficiency is demanded. In the present invention, two interferometers are disposed within the receiver so as to require no phase modulator within the receiver, thereby achieving a polarization-independent receiver. The pulses are paired, and the signal is transmitted with the relative phase, and the interval of the paired pulses is sufficiently reduced to set the optical path within the interferometer in the receiver to be smaller, thereby achieving the interferometer stabilized against thermal fluctuations.

Abstract: Methods and systems for detecting counterfeit optical communications products are described. An exemplary system includes a host device and a fiber optic component, such as an optical transceiver. The optical transceiver may include a TOSA, a ROSA, a controller circuit, and a memory module. The controller circuit may be operably connected to the TOSA, the ROSA, and the memory module. The host device may send a set of challenge data to the optical transceiver. The optical transceiver may respond with a data set encrypted by the controller circuit using a secret key stored in the memory module. The encrypted response data set may be evaluated to determine whether the optical transceiver is authenticate.

Abstract: A method and device for controlling security of a communication channel between an OLT and an ONU in a secure channel control system of EPON formed of the OLT and the ONU having a cryptographic module, a key management module and a transmitter/receiver for transmitting/receiving frames, the method comprising the steps of: a) distributing a key between the OLT and the ONU; b) transferring the distributed key to the encryption modules of the OLT and ONU; c) activating a corresponding encryption module using the distributed key at one of the OLT and the ONU which starts a security function activation; d) transmitting an encryption module information message including activation state information of the corresponding encryption module from the side (transmitting side) having the activated encryption module to an opponent side (receiving side); and e) activating an encryption module by checking activation state information of the encryption module at the receiving side.

Abstract: The quantum key distribution (QKD) systems (200, 300, 400) of the invention includes first and second QKD stations (Alice and Bob) according to the present invention, wherein either one or both QKD stations include fast optical switches (120, 220, 310, 320). Each fast optical switch is respectively optically coupled to two different round-trip optical paths (OP1 and OP2 at Alice, OP3 and OP4 at Bob) of different length that define respective optical path differences OPDA and OPDB, wherein OPDA=OPDB. By switching the fast optical switches using timed switching signals (S1-S3 at Alice, S4-S6 at Bob) from their corresponding controllers (CA at Alice, CB at Bob), the quantum signals—which can be single-photon or weak-coherent pulses—can be generated from a single optical pulse (112), randomly selectively encoded while traversing the optical paths in Alice and Bob, and then interfered and measured (detected) at Bob.

Abstract: In a method and apparatus for synchronizing the receiver and the emitter in an autocompensating quantum cryptography system it is allowed to one of the stations (for example the emitter) to define the timing of all its operations (for example the application of a signal onto the modulator used to encode the values of the bits) as a function of a time reference. This time reference can either be transmitted using a channel from the other station (for example the receiver). It can also consist of a time reference synchronized with that of the other station through using information transmitted along a channel and a synchronization unit. Preferably a time reference unit is provided at each station. One of these time reference units functions as a master, while the other one function as a slave. The slave is synchronized with the master using information transmitted over a communication channel by a synchronization unit.

Abstract: A space-based satellite device obtains one or more encryption key symbols. The satellite device transmits the one or more encryption key symbols to multiple nodes of a land-based network using quantum cryptographic mechanisms.

Abstract: A method (300) of performing photon detector autocalibration in quantum key distribution (QKD) system (200) is disclosed. The method (300) includes a first act (302) of performing a detector gate scan to establish the optimum arrival time of a detector gate pulse (S3) that corresponds with a maximum number of photon counts (NMAX) from a single-photon detector (216) in the QKD system (200). Once the optimal detector gate pulse arrival time is determined, then in an act (306), the detector gate scan is terminated and in an act (308) a detector gate dither process is initiated. The detector gate dither act (308) involves varying the arrival time (T) of the detector gate pulse (S3) around the optimal value of the arrival time established during the detector gate scan process. The detector gate dither provides minor adjustments to the arrival time to ensure that the detector (216) produces maximum number of photon counts (NMAX).

Abstract: Methods and systems for suppressing the electromagnetic interference (EMI) signature generated by a QKD station are disclosed. One of the methods includes generating two or more modulator drive signals corresponding to two or more of the n possible modulator states of the particular QKD protocol. The modulator drive signals are sent to a random number generation (RNG) unit, which randomly selects one of the two or more modulator drive signals and passes it to the modulator. Another method involves generating two modulator drive signals, wherein the voltage sum is constant. One signal is sent to the modulator while the other is sent to a circuit-terminating element, which can be a second modulator. The method suppresses the EMI signature associated with individual modulation states. This prevents an eavesdropper from gaining information about the modulator states via the EMI signature, which information could otherwise yield information about the exchanged key.

Abstract: A timing and synchronisation apparatus and method for a quantum cryptography system is disclosed. A gating pulse is generated by a clock and synchronised to the receipt of transmitted photons at the detector. The apparatus is arranged to only accept photon detection events occurring during the gating period.

Abstract: Systems and methods for transmitting quantum and classical signals over an optical network are disclosed, wherein the quantum signal wavelength either falls within the classical signal wavelength band, or is very close to one of the classical signal wavelengths. The system includes a deep-notch optical filter with a blocking bandwidth that includes the quantum signal wavelength but not any of the classical signal wavelengths. The deep-notch optical filtering is applied to the classical signals prior to their being multiplexed with the quantum signals to prevent noise generated by the classical signals from adversely affecting transmission of quantum signals in the transmission optical fiber. Narrow-band filtering is also applied to the quantum signals prior to their detection in order to substantially exclude spurious non-quantum-signal wavelengths that arise from non-linear effects in the optical fiber.

Abstract: The present invention provides a method for detecting a security module for link protection in an EPON, wherein an OLT and an ONU in the EPON can check whether or not an encryption module is present in each other and check the configuration of each other in order to avoid loss of a message when the message is encrypted for link protection between the OLT and the ONU in the EPON.

Abstract: An apparatus (1) and method for decoupling error correction from privacy amplification in a quantum key distribution (QKD 100) system includes two or more computer systems (102, 108) linked by quantum and classical channels (120, 122) where each computer system determines a generalized error syndrome associated with quantum communication between the systems, encrypts the generalized error syndrome using a sequence of values, and communicates the encrypted generalized error syndrome via a classical channel (128) to the other system, which uses the encrypted generalized error syndromes to compute error correction for the quantum transmission.

Abstract: A QKD arrangement with a photon source generating entangled idler and signal photons, with two measuring units, one of which receiving the idler photons and the other one receiving the signal photons, and each including an optical module with photon channels, wherein a photon passes a photon channel as a function of its polarization, and a device for detecting the photons in association to its respective photon channel, as well as a time control for timingly adjusting the detection devices; the photon source is adapted for pulsed emission of photon pairs, and an interrupting unit supplying the signal photons to the optical module in pulsed manner is arranged upstream of the other measuring unit, the photon channels in each optical module including delay units with different delay periods, and only one single-photon detector associates the photons to the photon channels on the basis of a time pattern.

Abstract: A system and method for securing communications between a plurality of users communicating over an optical network. The system utilizes a fixed or tunable source optical generator to generate entangled photon pairs, distribute the photons and establish a key exchange between users. The distribution of entangled photon pairs is implemented via at least one wavelength selective switch.

Abstract: The quantum key distribution (QKD) systems (200, 300, 400) of the invention includes first and second QKD stations (Alice and Bob) according to the present invention, wherein either one or both QKD stations include fast optical switches (120, 220, 310, 320). Each fast optical switch is respectively optically coupled to two different round-trip optical paths (OP1 and OP2 at Alice, OP3 and OP4 at Bob) of different length that define respective optical path differences OPDA and OPDB, wherein OPDA=OPDB. By switching the fast optical switches using timed switching signals (S1-S3 at Alice, S4-S6 at Bob) from their corresponding controllers (CA at Alice, CB at Bob), the quantum signals—which can be single-photon or weak-coherent pulses—can be generated from a single optical pulse (112), randomly selectively encoded while traversing the optical paths in Alice and Bob, and then interfered and measured (detected) at Bob.

Abstract: Key management and user authentication systems and methods for quantum cryptography networks that allow for users securely communicate over a traditional communication link (TC-link). The method includes securely linking a centralized quantum key certificate authority (QKCA) to each network user via respective secure quantum links or “Q-links” that encrypt and decrypt data based on quantum keys (“Q-keys”). When two users (Alice and Bob) wish to communicate, the QKCA sends a set of true random bits (R) to each user over the respective Q-links. They then use R as a key to encode and decode data they send to each other over the TC-link.

Abstract: Systems and methods for obtaining information on a key in the BB84 (Bennett-Brassard 1984) protocol of quantum key distribution are provided. A representative system comprises a quantum cryptographic entangling probe, comprising a single-photon source configured to produce a probe photon, a polarization filter configured to determine an initial probe photon polarization state for a set error rate induced by the quantum cryptographic entangling probe, a quantum controlled-NOT (CNOT) gate configured to provide entanglement of a signal with the probe photon polarization state and produce a gated probe photon so as to obtain information on a key, a Wollaston prism configured to separate the gated probe photon with polarization correlated to a signal measured by a receiver, and two single-photon photodetectors configured to measure the polarization state of the gated probe photon.

Abstract: A quantum key distribution method according to the present invention includes an error probability estimation step of estimating error probabilities of transmission data and the received data, an error correcting step of correcting errors in the received data based on error correcting information, a matching determination step of determining whether the transmission data and the received data after correcting errors match, and an information amount estimating step of estimating an amount of information leaked to an adversary through a quantum communication path, and further compresses data based on the amount of information made public in a process of processing via a public communication path and an estimated value of the amount of information leaked to the adversary through the quantum communication path to make the data after compression a cryptographic key shaped by devices.