Communication control techniques in quantum cryptographic communication system
AssigneeNEC Corporation
InventorHiroshi Imai
Life of this patent
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Abstract
A communication device can achieve SN ratio and stability of signal output an optical transmission line having the propagation characteristics susceptible to environmental changes. The communication device includes: an optical reception section configured to receive weak signal light and reference light arriving through the optical transmission line; an optical amplifier that amplifies received reference light; a probe light receiver that receives probe light arriving from the transmitting-side communication device through the optical transmission line; and a controller configured to calculate a transmission line state detected based on received probe light and control a gain of the optical amplifier according to the transmission line state.
Claims16
A communication device that detects a signal output by homodyne detection in a quantum cryptographic communication system, comprising:
- an optical reception section configured to receive signal light and reference light arriving from a transmitting-side communication device through an optical transmission line, wherein the optical transmission line has propagation characteristics of light varying due to changes of environment, wherein the signal light is weak light having quantum states and the reference light is light having no quantum states;
- an optical amplifier that amplifies received reference light;
- a homodyne detector configured to generate the signal output based on received signal light and the received reference light amplified by the optical amplifier;
- a probe light receiver that receives probe light arriving from the transmitting-side communication device through the optical transmission line;
- and
- a controller configured to:
- calculate a transmission line state detected based on received probe light;
- and control a gain of the optical amplifier according to the transmission line state.
A communication control method of a receiver in a quantum cryptographic communication system including a transmitter and the receiver which are optically connected to the transmitter through an optical transmission line having propagation characteristics of light varying due to changes of environment,
- the method comprising:
- by an optical reception section, receiving signal light, reference light and probe light arriving from the transmitter through the optical transmission line, wherein the signal light is weak light having quantum states and the reference light is light having no quantum states;
- by a controller, calculating a transmission line state detected based on received probe light and controlling an amplification factor of received reference light according to the transmission line state;
- and
- by a detector, detecting a signal output by homodyne detection based on the received signal light and the received reference light amplified at the amplification factor.
A quantum cryptographic communication system comprising a transmitter and a receiver, wherein
- the transmitter and the receiver are optically connected to each other through an optical transmission line having propagation characteristics of light varying due to changes of environment,
- the transmitter includes:
- an optical transmission section configured to generate signal light and reference light from coherent light, and transmit the signal light and the reference light to the optical transmission line, wherein the signal light is weak light having quantum states and the reference light is light having no quantum states;
- and
- a probe light transmitter configured to transmit probe light of a predetermined intensity to the optical transmission line,
- the receiver includes:
- an optical reception section configured to receive received signal light and received reference light arriving from the transmitter through the optical transmission line;
- an optical amplifier that amplifies the received reference light;
- a homodyne detector configured to generate a signal output based on the received signal light and the received reference light amplified by the optical amplifier;
- a probe light receiver that receives probe light arriving through the optical transmission line;
- and
- a controller configured to:
- calculate a transmission line state detected based on received probe light;
- and control a gain of the optical amplifier according to the transmission line state.
Dependencies are inferred from the claim text.