National Institute of Information and Communications Technology, Incorporated

National Institute of Information and Communications Technology, Incorporated Administrative Agency

Nec Corporation

Hokkaido University

The University of Tokyo

Communications Research Laboratory, Independent Administrative Institution

National Institutes of Natural Sciences

Mikio Fujiwara

Masahide Sasaki

Makoto Akiba

Akihisa Tomita

Ken-ichiro Yoshino

Morio Toyoshima

Masahiro Takeoka

Hiroshi Matsuo

Yoshihiro Nambu

Hiroo Kunimori

Hirohisa Nagata

Masato Koashi

Masao Nagasaki

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.

Photon detection device, reception device, quantum key distribution system, and method for detecting quantum signal

A personal information protection management system for genomic data includes data storage, role storage, a filter, and a data output part. The data storage is configured to store genomic data. The role storage is configured to store an identifier of a data output destination and a role in association with each other, the role including a detail of filtering for removing from genomic data a part that is not to be outputted. The filter is configured to filter the stored genomic data based on the stored role. The data output part is configured to output the filtered genomic data to the data output destination. The filter is configured to obtain a data request signal transmitted from the data output destination and, based on the role that is associated with the identifier included in the obtained data request signal, filter the genomic data.

Personal information protection management system for genomic data

An encryption key generating device includes a shared key separator separating a shared key into a first key and a second key and storing the first key in a non-volatile memory and storing the second key in a volatile memory; a key extender extending the second key to the same key length as that of the first key and storing the second key extended as a third key in the volatile memory; a key calculator calculating an encryption key by an exclusive-OR of the first key and the third key and storing it in the volatile memory.

Encryption key generating device, encryption key generating program, and encryption key generating/erasing method

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.

Transmitting device, receiving device, quantum key distribution method, and quantum key distribution program for quantum key distribution system

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.

Communication system

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.

Time-bin polarization format exchange technique for entangled optical source

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.

Apparatus and method for quantum cryptography communication

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.

Method for reducing low frequency noise of transistor

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.

Method for manufacturing photodetector for weak light

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.

Low-level light detector and low-level light imaging apparatus

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.

Photodetector for weak light with UV transparent substrates

This invention provides a photodetector for weak light and a weak light detection system including the photodetector for weak light the photodetector for weak light is comprised of a substrate on which an integrating read circuit including a PIN photodiode or an APD and an FET is mounted, wherein the entire assembly is mounted while separating the substrate from a ground potential without grounding the substrate, such a photodetector for weak light can reduce noise and ensure a high enough sensitivity enough to be able to discriminate the number of photons.

Photo detector for weak light

The present invention provides a photodetector for weak light that can release charge from the circuit without increasing capacity; the present invention being characterized by a photodetector for weak light that has a charge release means which permits the photodetector for weak light of the present invention to avoid increasing its capacity because it does not require a reset transistor integrated with the photodector, rather the charge reset means of the present invention lowers mounting capacity by removing itself from the circuit after it releases the charge.

Photodetector for weak light having charge reset means

The present invention relates to a method for reducing low-frequency noise in a cooled circuit wherein low-frequency noise in a cryogenic semiconductor device is reduced by carrying out thermal cure. The semiconductor device is turned on at a first temperature, and the temperature of the semiconductor device is temporarily raised, while flowing current in the semiconductor device, to a second temperature that is higher than the first temperature, and then cooling the temperature of the semiconductor device from the second temperature to a cryogenic temperature, at which the semiconductor device can operate.

Growing community of inventors

Koganei, Japan

Mikio Fujiwara