Abstract: An object is to prevent eavesdropping in quantum key distribution. A decoding unit decodes a quantum signal incident thereinto. A plurality of detect photons of the decoded quantum signal output from the decoding unit. A signal processing unit detects bits of the decoded quantum signal based on photon detection results of the plurality of detectors. A control unit perform switching processing by switching destinations to which two decoded quantum signals corresponding to one encoding basis are output between the plurality of detectors, and switching the bits detected by the signal processing unit based on the respective photon detection results of the plurality of detectors.

Abstract: An object is to prevent eavesdropping in quantum key distribution. A photon detector outputs an output current indicating a result of detecting a quantum signal. A current-voltage conversion unit converts the output current into an output voltage signal. An analog-to-digital converter outputs an output voltage signal obtained by analog-digital conversion of the output voltage signal. A signal processing unit performs predetermined signal processing on the output voltage signal, and outputs a photon detection signal indicating a result of detecting the quantum signal. When a time difference between a timing at which the quantum signal is incident into the photon detector and a reference timing determined based on a clock signal is not within a determination range, the photon detection signal is not output from the signal processing unit.

Abstract: A quantum key distribution device is provided with an encoding unit which encodes an optical pulse train; an intensity modulating unit which subjects the encoded optical pulse train to N (where N is an integer at least equal to 3) types of intensity modulation having mutually different intensities, with different timings; and a first key distillation processing unit which generates an encryption key on the basis of a data sequence obtained by removing data obtained from an optical pulse having a specific modulation pattern from a data sequence used by the encoding unit and the intensity modulating unit.

Abstract: A secret sharing storage system includes at least one user terminal, n units (n: an integer of 2 or more) of storage devices, and a main controller that is communicably connected to a random number generator. The main controller acquires a random number generated by the random number generator in a case of receiving original data sent from the user terminal, executes distributed processing on the original data by using the random number to generate n pieces of distributed data, and stores the n pieces of distributed data respectively in the corresponding n units of storage devices.

Abstract: A quantum key distribution device is provided with an encoding unit which encodes an optical pulse train; an intensity modulating unit which subjects the encoded optical pulse train to N (where N is an integer at least equal to 3) types of intensity modulation having mutually different intensities, with different timings; and a first key distillation processing unit which generates an encryption key on the basis of a data sequence obtained by removing data obtained from an optical pulse having a specific modulation pattern from a data sequence used by the encoding unit and the intensity modulating unit.

Abstract: Provided is a communication system in which a terminal communicates with a server via a portable communication network used for communication between smartphones. The smart phone includes first pre-shared key and encryption keys, the terminal includes a second pre-shared key, the server includes the encryption keys same as the encryption keys included in the smartphone, authentication between the terminal and the smartphone is performed by using the first pre-shared key and the second pre-shared key, and the terminal and the server perform communication via the smartphone by performing key synchronization of the encryption keys while setting a hash value of the encryption keys as an ID.

Abstract: Provided is a communication system in which a terminal communicates with a server via a portable communication network used for communication between smartphones. The smart phone includes first pre-shared key and encryption keys, the terminal includes a second pre-shared key, the server includes the encryption keys same as the encryption keys included in the smartphone, authentication between the terminal and the smartphone is performed by using the first pre-shared key and the second pre-shared key, and the terminal and the server perform communication via the smartphone by performing key synchronization of the encryption keys while setting a hash value of the encryption keys as an ID.

Abstract: It is an object of the present invention to provide a network system for quantum key distribution (QKD) for free space and fiber networks. The system of the present invention generates a couple of photons which have different wavelength and inputs each of the photons into the asymmetric Mach-Zehnder interferometer to obtain time-bin entangled state. It provides polarization information with one part of the photons. Then it can obtain hybrid quantum entanglement. The system of the present invention may be used hybrid quantum key distribution system applied for both free space and fibers.

Abstract: A quantum cryptography communication apparatus performs quantum cryptography communication between a transmitter and a receiver. The quantum cryptography communication apparatus includes first communicating unit transmitting and receiving a communication signal including relatively strong pulse light between the transmitter and the receiver, and second communicating unit transmitting and receiving a relatively weak quantum cryptography signal between the transmitter and the receiver in a period in which the communication signal is off and the attitude axis for the receiver can be adjusted to that for the transmitter by the second communicating unit.

Abstract: A method for reducing low frequency noise of a transistor operable at cryogenic temperatures includes a first step in which the transistor is illuminated with a light in a state that the transistor is activated and flowed current by supplying a power at a predetermined temperature, and a second step in which the transistor is operated at the predetermined temperature after the illumination of the light.

Abstract: It is an object of the present invention to provide a network system for quantum key distribution (QKD) for free space and fiber networks. The system of the present invention generates a couple of photons which have different wavelength and inputs each of the photons into the asymmetric Mach-Zehnder interferometer to obtain time-bin entangled state. It provides polarization information with one part of the photons. Then it can obtain hybrid quantum entanglement. The system of the present invention may be used hybrid quantum key distribution system applied for both free space and fibers.

Abstract: A method for reducing low frequency noise of a transistor operable at cryogenic temperatures includes a first step in which the transistor is illuminated with a light in a state that the transistor is activated and flowed current by supplying a power at a predetermined temperature, and a second step in which the transistor is operated at the predetermined temperature after the illumination of the light.

Abstract: A terminal (100) is provided with a first case having an operation section (102) including a plurality of operation keys (102a-102c); a second case, which is provided with a display (106) and is turnably arranged to the first case; an angle detector (202) for detecting a turning angle of the second case to the first case; and a controller (207) for changing allocation of functions to each of the operation keys (102a-102c) of the operation section (102), corresponding to the turning angle detected by the angle detector (202).

Abstract: A quantum cryptography communication apparatus performs quantum cryptography communication between a transmitter and a receiver. The quantum cryptography communication apparatus includes first communicating unit transmitting and receiving a communication signal including relatively strong pulse light between the transmitter and the receiver, and second communicating unit transmitting and receiving a relatively weak quantum cryptography signal between the transmitter and the receiver in a period in which the communication signal is off and the attitude axis for the receiver can be adjusted to that for the transmitter by the second communicating unit.

Abstract: The video signal processor of the present invention comprises a CCD for storing an inputted image by converting it into an electric charge through photoelectrical conversion to be stored by each field and then outputting the stored electric charge by each field; a shutter pulse generator for supplying a shutter pulse which adjusts storage time of the electric charge in the CCD; and a variable controller for variably controlling adjusting amount of electric charge storage time by the shutter pulse by a field unit.

Abstract: Again controller gain controls digitalized video signals for each minimum video unit. A variation controller establishes video blocks each consisting of a plurality of minimum video units, and also establishes a gain control value of the gain controller for each of the minimum video units constituting the established video blocks. The gain controller sequentially divides the video signals into the video blocks and gain controls, based on the gain control values, the respective minimum video units constituting each of the divided digital video blocks. In this way, there can be obtained a visual effect equivalent to a conversion of video signals such as 24P video signals to video signals such as 60I video signals by use of a conversion format such as 2:3 pull down method. Moreover, such visual effect can be realized without necessity of any frame memories and without implementing any complex timing controls.

Abstract: A low-level light detector includes an avalanche photodiode (APD) to which is applied a bias voltage adjusted to produce a multiplication factor of not more than 30, and a capacitor for accumulating carriers produced by light in the APD and multiplied using the APD characteristics, the capacitor being connected to the avalanche photodiode. The detector detects the intensity of light impinging on the avalanche photodiode by periodically reading the capacitor voltage and obtaining time-based differences in the voltage, or by resetting the capacitor voltage to a predetermined voltage each time the capacitor voltage is read.

Abstract: This invention provides a method for manufacturing a circuit for photon number counting without destroying a FET within the circuit by manufacturing a photodetector for weak light, the photodetector for weak light comprising a circuit on a substrate, the circuit comprising light detection means and a field effect transistor (FET), the method comprising: a light detection means connection step; an FET electrode-to-substrate electrode connection step; an external electrode connection step, a light detection means-to-gate connection step.

Abstract: A low-level light detector includes an avalanche photodiode (APD) to which is applied a bias voltage adjusted to produce a multiplication factor of not more than 30, and a capacitor for accumulating carriers produced by light in the APD and multiplied using the APD characteristics, the capacitor being connected to the avalanche photodiode. The detector detects the intensity of light impinging on the avalanche photodiode by periodically reading the capacitor voltage and obtaining time-based differences in the voltage, or by resetting the capacitor voltage to a predetermined voltage each time the capacitor voltage is read.

Abstract: The present invention provides a photodetector for weak light that can prevent noise from impurities, prevent electrodes from disconnecting from the substrate, and can be easily cooled; the present invention further provides a photodetector for weak light that can count the number of photons; the present invention solves the above problems by using an ultraviolet light transparent substrate on the photodetector for weak light.