Abstract: The present disclosure provides an information processing apparatus capable of improving the accuracy of solving a problem when an annealing algorithm is executed. An information processing apparatus 1 includes a calculation unit 2 and an arithmetic unit 4. The calculation unit 2 calculates at least one eigenvector of a coupling coefficient matrix including a coupling coefficient indicating a strength of interaction between each of a plurality of binary variables that indicate states of a plurality of respective spins in an Ising model, the coupling coefficient matrix being given in advance in accordance with a problem to be solved by an annealing algorithm. The arithmetic unit 4 executes the annealing algorithm from an initial state set based on the at least one eigenvector.

Abstract: The present disclosure provides an information processing apparatus capable of improving the accuracy of solving a problem when an annealing algorithm is executed. An information processing apparatus 1 includes a calculation unit 2 and an arithmetic unit 4. The calculation unit 2 calculates at least one eigenvector of a coupling coefficient matrix including a coupling coefficient indicating a strength of interaction between each of a plurality of binary variables that indicate states of a plurality of respective spins in an Ising model, the coupling coefficient matrix being given in advance in accordance with a problem to be solved by an annealing algorithm. The arithmetic unit 4 executes the annealing algorithm from an initial state set based on the at least one eigenvector.

Abstract: In order to provide an optical sensor that is capable of obtaining both an optical trap effect and a moth eye effect with a single texture structure, a semiconductor optical sensor according to the present invention includes a light absorption medium that has a refractive index n and a thickness sufficiently less than a light transmission length, wherein the center wavelength to be observed is defined as ?. The semiconductor optical sensor is characterized by: having, in a light incident surface, a texture structure having a random surface direction and a typical structure scale d defined as in (?/n).

Abstract: In order to provide an optical sensor that is capable of obtaining both an optical trap effect and a moth eye effect with a single texture structure, a semiconductor optical sensor according to the present invention includes a light absorption medium that has a refractive index n and a thickness sufficiently less than a light transmission length, wherein the center wavelength to be observed is defined as ?. The semiconductor optical sensor is characterized by: having, in a light incident surface, a texture structure having a random surface direction and a typical structure scale d defined as in (?/n).

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: 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: In a quantum cryptography key distribution system for sharing a secret key between a transmitter and a receiver site, an unbalanced interferometer system in the transmitter site has a Mach-Zehnder interferometer switch with a phase modulator while the receiver site records photon arrival time slots. The system utilizes a whole of arrival photons in the receiver site and dispenses with any phase modulator in the receiver site. This system serves to improve a photon utilization efficiency.

Abstract: A quantum cryptography transmission system according to the present invention comprises a transmission device (10A), a reception device (20A), and a transmission path (30) configured to connect between the devices. The transmission device includes a light emitting unit (11) configured to emit photons serving as quantum bit information carriers, and a transmission-side optical circuit (12A). The reception device includes a light receiving unit (21) configured to detect photons serving as quantum bit information carriers, and a reception-side optical circuit (22A). Each of the transmission-side optical circuit (12A) and reception-side optical circuit (22A) is an optical circuit which is configured of an unbalanced Mach-Zehnder interferometer (123; 223) including an optical delay circuit (123-1; 223-1) in one arm thereof, and two transmission-side 3-dB couplers (126; 226) and (127; 227) to be connected to the two arms of the unbalanced Mach-Zehnder interferometer (123; 223), respectively.

Abstract: A quantum encryption device comprises a faint laser light source for generating a photon serving as a qubit information carrier, three or more asymmetric Mach-Zehnder interference systems each formed by a photonic lightwave circuit, an optical transmission path for transmitting the photon, a photo detector, a device for recording sending data of a sender and observational data of a receiver, and a classic communication path for performing classic communication with a regular user.

Abstract: At a sender site of a secure communication network, a first coherent light pulse sequence is phase modulated with a random bit sequence by a phase modulator, and a second coherent light pulse sequence synchronised to the first coherent light pulse sequence is transformed by an optical transducer to a superposition of coherent states. The outputs of the modulator and the transducer are multiplexed and transmitted over an optical communication link. At a receiver site, a homodyne detector receives the transmitted light pulse sequence and detects a random bit sequence and a superposition of quantum states.

Abstract: A method for testing the reliability of a quantum key distribution apparatus is provided. The method includes the steps of: producing a set of quanta by the sender, the set of quanta comprising first, second, and third quantum, the first, second, and third quantum having a quantum correlation; measuring the first and second quantum at a sender using one of two prearranged bases; transmitting the third quantum to the receiver over the quantum channel; measuring the third quantum at a receiver using one of the two prearranged bases; and exchanging information regarding the measured bases between the sender and receiver over a public channel to check for a known behavior of the quantum apparatus based upon the quantum correlation, wherein if the quantum apparatus behaves as is known or within a tolerable limit the reliability of the quantum apparatus is confirmed. A similar method for quantum key distribution is also disclosed.

Abstract: In a quantum cryptography key distribution system for sharing a secret key between a transmitter and a receiver site, an unbalanced interferometer system in the transmitter site has a Mach-Zehnder interferometer switch with a phase modulator while the receiver site records photon arrival time slots. The system utilizes a whole of arrival photons in the receiver site and dispenses with any phase modulator in the receiver site. This system serves to improve a photon utilization efficiency.

Abstract: A quantum cryptography multi-node communication system includes a quantum communication channel and a plurality of nodes including a transmission node and a reception node and connected with the quantum communication channel. The transmission node transmits a light signal as a time series of photons to the reception node through the quantum communication channel, a quantum state of the photons is modulated, and transmits a quantum state sequence to the reception node. The reception node predetermines a quantum state sequence, receives the light signal transmitted from the transmission node, measures quantum states of the received light signal, and determines presence or absence of interception based on the predetermined quantum state sequence, the transmitted quantum state sequence and the measured quantum states.

Abstract: A mode-locked semiconductor laser includes a gain region formed from a semiconductor gain material of two or three dimensional carrier confinement structure having a size on the order of a thermal de-Broglie wavelength, the size of the semiconductor of the carrier confinement structure being controlled such that the gain spectrum has discrete peaks at a frequency period which is an integer power of the reciprocal of the round-trip time of light in the optical resonator.