Control device, quantum cryptographic communication system, control method, and computer program product

1 . A control device comprising:

one or more processors configured to:

acquire information indicating a state of quantum communication of a quantum communication path from a plurality of reception devices that receive photons via the quantum communication path, and determine resources to be allocated to a plurality of key distillation modules of a server device based on the information indicating the state of the quantum communication, wherein the information indicating the state of the quantum communication path includes at least one of a quantum bit error rate, a number of detected photons, or a number of detected decoy pulses, and wherein the one or more processors are further configured to perform at least one of a first step, a second step, a third step, a fourth step, or a fifth step,

the first step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first quantum communication path in which the QBER is a first value less than or equal to a predetermined value, the second key distillation module being configured to perform key distillation of photons received by a second quantum communication path in which the QBER is a second value larger than the first value and less than or equal to the predetermined value; and

determining not to allocate the resources to a third key distillation module, of the plurality of key distillation modules, configured to perform key distillation of photons received by a third quantum communication path in which the QBER exceeds the predetermined value;

the second step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons in which key length, calculated based on the number of detected photons and the QBER, is a first value, the second key distillation module being configured to perform key distillation of photons in which the key length is a second value longer than the first value;

the third step comprising:

loosening a degree of allocating the resources more, according to an increase in the QBER, than an allocation amount of the resources when the QBER increases from a first value to a second value in a case where an error correction algorithm is a cascade method and an allocation amount of the resources when the QBER increases from the first value to the second value in a case where the error correction algorithm is a low density parity check (LDPC);

the fourth step comprising:

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first reception device in which a difference between the number of detected decoy pulses and a predetermined value is a first value, the second key distillation module being configured to perform key distillation of photons received by a second reception device in which the difference is a second value larger than the first value;

the fifth step comprising:

acquiring, from a first reception device, first numerical information indicating performance of hardware of the first reception device;

further acquiring, from a second reception device, second numerical information indicating that performance of hardware is higher than that of the first numerical information; and

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

the sixth step comprising:

acquiring, from a first reception device, first operation information indicating an operation state of the first reception device, and further acquire, from a second reception device, second operation information indicating an operation state of the second reception device;

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device when a period, during which the second reception device is operating normally, indicated by the operating state of the second operating information is longer than a period, during which the first reception device is operating normally, indicated by the operating state of the first operating information, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

determining not to allocate the resources to the first key distillation module when the first operating information indicates that the first reception device is not operating; and

output circuitry configured to output resource information indicating the resources to be allocated to the plurality of key distillation modules of the server device.

2 . The device according to claim 1 , wherein

the resource information includes at least one of information indicating a ratio of using a processor of the server device, information indicating a ratio of using a main storage device of the server device, and information indicating a ratio of using an auxiliary storage device of the server device.

3 . A quantum cryptographic communication system comprising:

a control device comprising:

one or more processors configured to acquire information indicating a state of quantum communication of a quantum communication path from a plurality of reception devices that receive photons via the quantum communication path, and determine resources to be allocated to a plurality of key distillation modules of a server device based on the information indicating the state of the quantum communication, wherein the information indicating the state of the quantum communication path includes at least one of a quantum bit error rate, a number of detected photons, or a number of detected decoy pulses, and wherein the one or more processors are further configured to perform at least one of a first step, a second step, a third step, a fourth step, or a fifth step,

the first step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first quantum communication path in which the QBER is a first value less than or equal to a predetermined value, the second key distillation module being configured to perform key distillation of photons received by a second quantum communication path in which the QBER is a second value larger than the first value and less than or equal to the predetermined value; and

determining not to allocate the resources to a third key distillation module, of the plurality of key distillation modules, configured to perform key distillation of photons received by a third quantum communication path in which the QBER exceeds the predetermined value;

the second step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons in which key length, calculated based on the number of detected photons and the QBER, is a first value, the second key distillation module being configured to perform key distillation of photons in which the key length is a second value longer than the first value;

the third step comprising:

loosening a degree of allocating the resources more, according to an increase in the QBER, than an allocation amount of the resources when the QBER increases from a first value to a second value in a case where an error correction algorithm is a cascade method and an allocation amount of the resources when the QBER increases from the first value to the second value in a case where the error correction algorithm is a low density parity check (LDPC);

the fourth step comprising:

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first reception device in which a difference between the number of detected decoy pulses and a predetermined value is a first value, the second key distillation module being configured to perform key distillation of photons received by a second reception device in which the difference is a second value larger than the first value;

the fifth step comprising:

acquiring, from a first reception device, first numerical information indicating performance of hardware of the first reception device;

further acquiring, from a second reception device, second numerical information indicating that performance of hardware is higher than that of the first numerical information; and

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

the sixth step comprising:

acquiring, from a first reception device, first operation information indicating an operation state of the first reception device, and further acquire, from a second reception device, second operation information indicating an operation state of the second reception device;

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device when a period, during which the second reception device is operating normally, indicated by the operating state of the second operating information is longer than a period, during which the first reception device is operating normally, indicated by the operating state of the first operating information, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

determining not to allocate the resources to the first key distillation module when the first operating information indicates that the first reception device is not operating;

output circuitry configured to output resource information indicating the resources to be allocated to the plurality of key distillation modules of the server device;

a plurality of transmission devices configured to transmit the photons via the quantum communication path;

a transmission server device connected to the plurality of transmission devices;

the plurality of reception devices configured to receive the photons via the quantum communication path; and

a reception server device connected to the plurality of reception devices.

4 . The system according to claim 3 , wherein

the reception server device is connected to a plurality of the transmission server devices via the plurality of reception devices, the quantum communication path, and the plurality of transmission devices.

5 . The system according to claim 3 , wherein

the transmission server device is connected to a plurality of the reception server devices via the plurality of transmission devices, the quantum communication path, and the plurality of reception devices.

6 . The system according to claim 3 , wherein

the quantum communication path includes a plurality of optical fiber links, and

the plurality of transmission devices and the plurality of reception devices are connected by the plurality of optical fiber links.

7 . The system according to claim 3 , further comprising:

a first multiplexer configured to perform optical wavelength multiplexing on photons transmitted from the plurality of transmission devices; and

a second multiplexer configured to receive the optical wavelength multiplexed photons, wherein

the quantum communication path includes one optical fiber link.

8 . A control method comprising:

acquiring, by a control device, information indicating a state of quantum communication of a quantum communication path from a plurality of reception devices that receive photons via the quantum communication path, and determining resources to be allocated to a plurality of key distillation modules of a server device based on the information indicating the state of the quantum communication, wherein the information indicating the state of the quantum communication path includes at least one of a quantum bit error rate, a number of detected photons, or a number of detected decoy pulses, and wherein the method further includes performing at least one of a first step, a second step, a third step, a fourth step, or a fifth step,

the first step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first quantum communication path in which the QBER is a first value less than or equal to a predetermined value, the second key distillation module being configured to perform key distillation of photons received by a second quantum communication path in which the QBER is a second value larger than the first value and less than or equal to the predetermined value; and

determining not to allocate the resources to a third key distillation module, of the plurality of key distillation modules, configured to perform key distillation of photons received by a third quantum communication path in which the QBER exceeds the predetermined value;

the second step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons in which key length, calculated based on the number of detected photons and the QBER, is a first value, the second key distillation module being configured to perform key distillation of photons in which the key length is a second value longer than the first value;

the third step comprising:

loosening a degree of allocating the resources more, according to an increase in the QBER, than an allocation amount of the resources when the QBER increases from a first value to a second value in a case where an error correction algorithm is a cascade method and an allocation amount of the resources when the QBER increases from the first value to the second value in a case where the error correction algorithm is a low density parity check (LDPC);

the fourth step comprising:

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first reception device in which a difference between the number of detected decoy pulses and a predetermined value is a first value, the second key distillation module being configured to perform key distillation of photons received by a second reception device in which the difference is a second value larger than the first value;

the fifth step comprising:

acquiring, from a first reception device, first numerical information indicating performance of hardware of the first reception device;

further acquiring, from a second reception device, second numerical information indicating that performance of hardware is higher than that of the first numerical information; and

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

the sixth step comprising:

acquiring, from a first reception device, first operation information indicating an operation state of the first reception device, and further acquire, from a second reception device, second operation information indicating an operation state of the second reception device;

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device when a period, during which the second reception device is operating normally, indicated by the operating state of the second operating information is longer than a period, during which the first reception device is operating normally, indicated by the operating state of the first operating information, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

determining not to allocate the resources to the first key distillation module when the first operating information indicates that the first reception device is not operating; and

outputting, by the control device, resource information indicating the resources to be allocated to the plurality of key distillation modules of the server device.

9 . A computer program product comprising a non-transitory computer-readable medium including programmed instructions, the instructions causing a computer to execute:

acquiring, information indicating a state of quantum communication of a quantum communication path from a plurality of reception devices that receive photons via the quantum communication path, and determining resources to be allocated to a plurality of key distillation modules of a server device based on the information indicating the state of the quantum communication, wherein the information indicating the state of the quantum communication path includes at least one of a quantum bit error rate, a number of detected photons, or a number of detected decoy pulses, and wherein the instructions further cause the computer to perform at least one of a first step, a second step, a third step, a fourth step, or a fifth step,

the first step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first quantum communication path in which the QBER is a first value less than or equal to a predetermined value, the second key distillation module being configured to perform key distillation of photons received by a second quantum communication path in which the QBER is a second value larger than the first value and less than or equal to the predetermined value; and

determining not to allocate the resources to a third key distillation module, of the plurality of key distillation modules, configured to perform key distillation of photons received by a third quantum communication path in which the QBER exceeds the predetermined value;

the second step comprising:

determining to allocate the resources more to a second key distillation module other than to a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons in which key length, calculated based on the number of detected photons and the QBER, is a first value, the second key distillation module being configured to perform key distillation of photons in which the key length is a second value longer than the first value;

the third step comprising:

loosening a degree of allocating the resources more, according to an increase in the QBER, than an allocation amount of the resources when the QBER increases from a first value to a second value in a case where an error correction algorithm is a cascade method and an allocation amount of the resources when the QBER increases from the first value to the second value in a case where the error correction algorithm is a low density parity check (LDPC);

the fourth step comprising:

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by a first reception device in which a difference between the number of detected decoy pulses and a predetermined value is a first value, the second key distillation module being configured to perform key distillation of photons received by a second reception device in which the difference is a second value larger than the first value;

the fifth step comprising:

acquiring, from a first reception device, first numerical information indicating performance of hardware of the first reception device;

further acquiring, from a second reception device, second numerical information indicating that performance of hardware is higher than that of the first numerical information; and

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

the sixth step comprising:

acquiring, from a first reception device, first operation information indicating an operation state of the first reception device, and further acquire, from a second reception device, second operation information indicating an operation state of the second reception device;

determining to allocate the resources more to a second key distillation module other than a first key distillation module among the plurality of key distillation modules, the first key distillation module being configured to perform key distillation of photons received by the first reception device when a period, during which the second reception device is operating normally, indicated by the operating state of the second operating information is longer than a period, during which the first reception device is operating normally, indicated by the operating state of the first operating information, the second key distillation module being configured to perform key distillation of photons received by the second reception device; and

determining not to allocate the resources to the first key distillation module when the first operating information indicates that the first reception device is not operating; and

outputting resource information indicating the resources to be allocated to the plurality of key distillation modules of the server device.