Quantum cryptographic communication system, communication device, and control method thereof
AssigneeNEC Corporation
InventorHiroshi IMAI
Life of this patent
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Abstract
A quantum cryptographic communication system includes a transmitter (Alice) and a receiver (Bob) which are optically connected through an optical transmission line. The transmitter transmits signal light having a quantum state and reference light having no quantum state to the receiver through the optical transmission line. The receiver includes an optical amplifier that amplifies the reference light; a homodyne detector that generates a signal output based on amplified reference light and the received signal light; a level detector that detects a signal output level from the signal output; and an optical amplifier controller that controls a gain of the optical amplifier based on at least the signal output level.
Claims14
A quantum cryptographic communication system comprising a transmitter and a receiver which are connected via a communication network,
- wherein the transmitter and the receiver are optically connected through an optical transmission line,
- the transmitter comprises
- an optical transmission section configured to transmit signal light having a quantum state and reference light having no quantum state to the receiver through the optical transmission line, wherein the signal light and the reference light are generated from coherent light and
- the receiver comprises:
- an optical reception section configured to receive receiving-side signal light and receiving-side reference light arriving through the optical transmission line;
- an optical amplifier that amplifies the receiving-side reference light while maintaining wavelength and phase of the receiving-side reference light;
- a homodyne detector that generates a signal output based on the receiving-side reference light amplified by the optical amplifier and the receiving-side signal light;
- a level detector that detects a signal output level from the signal output;
- and
- an optical amplifier controller that controls a gain of the optical amplifier based on at least the signal output level.
A receiving-side communication device that detects a signal output by homodyne detection from signal light and reference light transmitted by a transmitting-side communication device through an optical transmission line in a quantum cryptographic communication system, wherein the signal light and the reference light are generated from coherent light, wherein the signal light is weak-intensity light having a quantum state and the reference light is light having no quantum state, the receiving-side communication device comprising:
- an optical reception section configured to receive receiving-side signal light and receiving-side reference light from the transmitting-side communication device through the optical transmission line;
- an optical amplifier that amplifies the receiving-side reference light received by the optical reception section while maintaining wavelength and phase of the receiving-side reference light;
- a homodyne detector that generates the signal output based on the receiving-side reference light amplified by the optical amplifier and the receiving-side signal light;
- a level detector that detects a signal output level from the signal output;
- and
- an optical amplifier controller that controls a gain of the optical amplifier based on at least the signal output level.
A control method in a receiving-side communication device that detects a signal output by homodyne detection from signal light and reference light transmitted by a transmitting-side communication device through an optical transmission line in a quantum cryptographic communication system, wherein the signal light and the reference light are generated from coherent light, wherein the signal light is weak-intensity light having a quantum state and the reference light is light having no quantum state, the control method comprising:
- by an optical reception section, receiving receiving-side signal light and receiving-side reference light from the transmitting-side communication device through the optical transmission line;
- by an optical amplifier, amplifying the receiving-side reference light received by the optical reception section while maintaining wavelength and phase of the receiving-side reference light;
- by a homodyne detector, generating the signal output based on receiving-side reference light and the receiving-side signal light;
- by a level detector, detecting a signal output level from the signal output;
- and
- by an optical amplifier controller, controlling a gain of the optical amplifier based on at least the signal output level.
Dependencies are inferred from the claim text.