Communication system, communication method, and program

Abstract

A generation device (51) comprises a first access control unit (12) that performs authentication with use devices (61A, 61B), a first communication unit (15) that performs quantum entanglement communication with the use devices, and a first reservation unit (14) that reserves resources for the use devices when the first communication unit performs quantum entanglement communication. The use device comprises a second access control unit (22) that performs authentication with the generation device, a second communication unit (25) that performs quantum entanglement communication with the generation device, and a second reservation unit (24) that reserves resources for the generation device when the second communication unit performs quantum entanglement communication. The first reservation unit prohibits access other than that from the use devices in a period reserved by the first reservation unit, and the second reservation unit prohibits access other than that from the generation device in a period reserved by the second reservation unit.

Description

Communication system, communication method, and program

[0001] The present disclosure relates to a communication system, a communication method, and a program for performing quantum entanglement communication.

[0002] In order to achieve highly confidential communications, Non-Patent Documents 1 and 2 propose a communication system using quantum key distribution (QKD), in which both the transmitting node and the receiving node share a secret key that is difficult for others to eavesdrop on. Non-Patent Document 3 also defines the functions of a control unit in QKD.

[0003] Furthermore, quantum entanglement distribution has been proposed as an application of quantum communication. Quantum entanglement distribution is a communication method that shares quantum states among multiple distant locations by sharing quantum entanglement at different locations, and is expected to be applied to distributed quantum computers, distributed sensors, etc.

[0004] Quantum entanglement distribution is not limited to one-to-one communication between a sending node and a receiving node, as in the above-mentioned QKD. Non-Patent Document 4 proposes a method for sharing quantum entanglement among multiple parties, where multiple servers communicate with each other and simultaneously perform calculations.

[0005] Hiroki Takesueet al. "Quantum key distribution over a 40-dBchannel loss using superconducting single-photon detectors." Nature photonics 1.6 (2007): 343-348. Masahide Sasakiet al. "Field test of quantum key distribution in the TokyoQKD Network." Opticsexpress 19.11 (2011):10387-10409.ITU-T Y.3802Quantum Key distribution networks,Functional architecture 12 / 2020H. Lo et al. "Three-photon time-binentanglement generation using an optical switch," in Proceedings of the 2022 Conference on Lasers and Electro-Optics PacificRim, Technical DigestSeries (Optica Publishing Group, 2022), paperCThA7E_02.

[0006] In the above-mentioned QKD, since it is one-to-one communication between a sending node and a receiving node, a method of transmitting a quantum from the sending node to the receiving node can be adopted. On the other hand, in multi-party quantum entanglement communication, the receiving user device needs to request the sending of quantum entangled light from the generating device and the sending user device that share the quantum entanglement. However, there is a possibility that the resources provided in the generating device and the sending user device cannot be used due to contention caused by access from other nodes.

[0007] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a communication system, a communication method, and a program that can reliably perform quantum entanglement communication between a quantum entanglement generation device and a quantum entanglement utilization device.

[0008] A communication system according to one aspect of the present disclosure is a communication system that performs quantum entanglement communication between a generating device that generates quantum entanglement via a network and a user device that uses the quantum entanglement, wherein the generating device comprises a first access control unit that authenticates the user device, a first communication unit that performs quantum entanglement communication with the user device, and a first reservation unit that reserves resources of the user device when performing quantum entanglement communication via the first communication unit; the user device comprises a second access control unit that authenticates the generating device, a second communication unit that performs quantum entanglement communication with the generating device, and a second reservation unit that reserves resources of the generating device when performing quantum entanglement communication via the second communication unit; the first reservation unit prohibits access by any device other than the user device during the period reserved by the first reservation unit, and the second reservation unit prohibits access by any device other than the generating device during the period reserved by the second reservation unit.

[0009] A communication method of one aspect of the present disclosure is a communication method for performing quantum entanglement communication between a generating device that generates quantum entanglement and a user device that uses the quantum entanglement via a network, wherein when performing quantum entanglement communication between a first communication unit provided in the generating device and a second communication unit provided in the user device, a first reservation unit provided in the generating device reserves resources of the user device, a second reservation unit provided in the user device reserves resources of the generating device, the first reservation unit prohibits access by any device other than the user device during the period reserved by the first reservation unit, and the second reservation unit prohibits access by any device other than the generating device during the period reserved by the second reservation unit.

[0010] One aspect of the present disclosure is a program for causing a computer to function as a generating device or a utilizing device of a communication system.

[0011] According to the present disclosure, it becomes possible to reliably perform quantum entanglement communication between a quantum entanglement generating device and a quantum entanglement utilizing device.

[0012] FIG. 1 is a block diagram showing a schematic configuration of a communication system E1 according to a first embodiment. FIG. 2 is a block diagram showing detailed configurations of a generating device and a using device in the communication system according to the first embodiment. FIG. 3 is a flowchart showing a processing procedure of the communication system according to the first embodiment. FIG. 4 is a block diagram showing detailed configurations of a generating device and a using device in the communication system according to the second embodiment. FIG. 5 is a flowchart showing a processing procedure of the communication system according to the second embodiment. FIG. 6 is a block diagram showing detailed configurations of a generating device and a using device in the communication system according to the third embodiment. FIG. 7 is an explanatory diagram showing a connection state of each generating device and each using device in the communication system according to the fourth embodiment. FIG. 8 is an explanatory diagram showing a connection state of each generating device and each using device in the communication system according to the fifth embodiment. FIG. 9 is a block diagram showing a hardware configuration of this embodiment.

[0013] [Description of First Embodiment] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a communication system E1 according to the first embodiment. As shown in FIG. 1, the communication system E1 according to the first embodiment includes a generating device 51 that generates quantum entanglement and utilization devices 61A and 61B that transmit and receive various information using quantum entanglement. The generating device 51 and utilization devices 61A and 61B are connected to a network NW using optical lines. The communication system E1 performs quantum entanglement communication between the generating device 51 that generates quantum entanglement and the utilization devices 61A and 61B that utilize quantum entanglement via the network NW.

[0014] The utilization device 61A is, for example, a sending node, and the utilization device 61B is, for example, a receiving node. When transmitting information from the utilization device 61A to the utilization device 61B, the generation device 51 transmits quantum entangled light to each of the utilization devices 61A and 61B. The utilization device 61A (sending node) transfers the information to be transmitted into quantum entangled light, and transmits the information to the utilization device 61B (receiving node), thereby performing quantum entanglement communication between the two utilization devices 61A and 61B.

[0015] 1 illustrates a configuration including one generating device 51, multiple generating devices may be connected to the network NW. Also, while two using devices 61A and 61B are illustrated in FIG. 1, three or more using devices may be connected to the network NW.

[0016] 2 is a block diagram showing the detailed configuration of the generation device 51 and the utilization devices 61A and 61B. As shown in FIG. 2, the generation device 51 includes a communication control unit 11, a first access control unit 12, a classical communication unit 13, a first reservation unit 14, and a first communication unit 15.

[0017] When communicating various information from the user device 61A to the user device 61B, the generation device 51 performs classical communication with each of the user devices 61A and 61B. In addition, the generation device 51 shares quantum entanglement with each of the user devices 61A and 61B by transmitting quantum entangled light to each of the user devices 61A and 61B. Sharing quantum entanglement enables information communication using quantum entanglement between the user devices 61A and 61B.

[0018] The communication control unit 11 controls communication by the classical communication unit 13 and quantum entanglement communication by the first communication unit 15. The communication control unit 11 may execute policy control for applications.

[0019] The first access control unit 12 performs authentication with the second access control unit 22 provided in the devices to be used 61A and 61B. That is, the first access control unit 12 performs authentication with the devices to be used 61A and 61B.

[0020] The classical communication unit 13 performs classical communication with the classical communication units 23 of the utilization devices 61A and 61B.

[0021] The first communication unit 15 performs quantum entanglement communication with the utilization devices 61A and 61B. The first communication unit 15 generates quantum entanglement in quantum entangled light. For example, a beam splitter or parametric down-conversion may be used as a method for generating quantum entanglement. Alternatively, Bell measurement for transferring quantum entanglement or quantum entanglement swapping between photons and matter may be used.

[0022] The quantum entangled light may be encoded by polarization, by encoding by orthogonal components of squeezed light, or by generating quantum entanglement using time bin coding. The first communication unit 15 may also include an entanglement source generator that generates quantum entanglement and a separator that separates the quantum entanglement according to its destination. The quantum entangled light generated by the first communication unit 15 is transmitted to the utilization devices 61A and 61B.

[0023] When a user performs a reservation operation, the first reservation unit 14 reserves hardware and software (hereinafter referred to as "resources") that execute the functions of the generation device 51 and the utilization devices 61A and 61B. That is, the first reservation unit 14 reserves the resources of the utilization devices 61A and 61B when quantum entanglement communication is performed by the first communication unit 15.

[0024] For example, when sharing quantum entanglement between the generation device 51 and two user devices 61A and 61B, the user performs a reservation operation in advance in the first reservation unit 14. When the user performs a reservation operation, the first reservation unit 14 performs control to prohibit access to the generation device 51 and the user devices 61A and 61B from other communication units until the reserved period has elapsed. In other words, the first reservation unit 14 prohibits access from devices other than the user devices 61A and 61B during the period reserved by the first reservation unit 14. Resources for the generation device 51 and the user devices 61A and 61B are secured during the reserved period. This allows the generation device 51 and the user devices 61A and 61B to perform quantum entanglement communication without being affected by the other communication units.

[0025] The utilization device 61A includes a communication control unit 21, a second access control unit 22, a classical communication unit 23, a second reservation unit 24, and a second communication unit 25.

[0026] The communication control unit 21 controls communication by the classical communication unit 23 and quantum entanglement communication by the second communication unit 25. The communication control unit 21 may execute policy control for applications.

[0027] The second access control unit 22 performs authentication with the first access control unit 12 provided in the generating device 51. That is, the second access control unit 22 performs authentication with the generating device 51.

[0028] The classical communication unit 23 performs classical communication with the classical communication unit 13 installed in the generation device 51 .

[0029] The second communication unit 25 performs quantum entanglement communication with the generation device 51. The second communication unit 25 generates quantum entanglement in quantum entangled light. As described above, a beam splitter or parametric down-conversion can be used as a method for generating quantum entanglement. Alternatively, Bell measurement for transferring quantum entanglement or quantum entanglement swapping between photons and matter can also be used. The encoding of the quantum entangled light can be polarization encoding, encoding using orthogonal components of squeezed light, or quantum entanglement generation using time-bin encoding.

[0030] The second communication unit 25 may include an entangled light measurement unit that measures the correlation of the quantum entanglement transmitted to the utilization device 61A and the utilization device 61B, and an entangled light decoding unit that decodes the entangled light. The utilization devices 61A and 61B may include a photon detector, a time measurement unit, a coincidence measurement unit, an error correction unit, etc. The quantum entangled light generated by the second communication unit 25 is transmitted to the generation device 51.

[0031] Alternatively, in contrast to the above example, the second communication unit 25 of the utilization devices 61A and 61B may include an entanglement source generation unit, and the first communication unit 15 of the generation device 51 may include an entanglement transition unit. The entanglement transition unit has a function of transferring information to be transmitted into quantum entanglement.

[0032] When a reservation operation is performed by a user, the second reservation unit 24 reserves the resources of the generation device 51 and the utilization devices 61A and 61B. That is, the second reservation unit 24 reserves the resources of the generation device 51 when quantum entanglement communication is performed by the second communication unit 25.

[0033] For example, when quantum entanglement is to be shared between the generating device 51 and two user devices 61A and 61B, the user performs a reservation operation in advance in the second reservation unit 24. When the user performs a reservation operation, the second reservation unit 24 performs control to prohibit access to the generating device 51 and the user devices 61A and 61B from other communication units until the reserved period has elapsed. In other words, the second reservation unit 24 prohibits access from devices other than the generating device 51 during the period reserved by the second reservation unit 24. Resources for the generating device 51 and the user devices 61A and 61B are secured during the reserved period. This allows the generating device 51 and the user devices 61A and 61B to perform quantum entanglement communication without being affected by the other communication units.

[0034] Since the user device 61A and the user device 61B have the same configuration, the detailed configuration of the user device 61B is omitted in FIG.

[0035] Next, the processing procedure of the communication system E1 according to the first embodiment configured as described above will be described with reference to the flowchart shown in FIG.

[0036] First, in step S11 of FIG. 3, the second access control unit 22 of the receiving-side utilization device 61B authenticates the transmitting-side utilization device 61A and the generating device 51, and requests delivery of quantum entanglement.

[0037] In step S12, the communication control unit 21 of the utilization device 61B sets conditions such as the entanglement method, distance, wavelength, frequency, data size, fidelity, etc. to be used in the quantum entanglement communication. The classical communication unit 23 notifies the generation device 51 and the receiving-side utilization device 61B of the set conditions.

[0038] The entanglement method includes a polarization-based entanglement method and a time-based encoding entanglement method. The distance indicates the distance of the quantum entanglement communication. The frequency is the interval between pulses that encode the entangled light. The data size is set based on the computational resources available for processing at the destination utilization device 61B. The fidelity is an index that indicates the similarity of the quantum states between quantum entanglements.

[0039] In step S13, the second communication unit 25 of the transmitting device 61A determines whether or not the device can comply with the conditions set in step S12. If the device can comply (YES in step S13), the process proceeds to step S16; if not (NO in step S13), the process proceeds to step S14.

[0040] In step S14, the communication control unit 11 of the generating device 51 requests the receiving device 61B to change the above conditions.

[0041] In step S15, the device 61B determines whether the conditions can be changed. If the conditions can be changed (S15; YES), the process returns to step S12. If not (S15; NO), the process ends.

[0042] In step S16, the first reservation unit 14 reserves the resources of the utilization devices 61A and 61B for a certain period of time. The second reservation unit 24 reserves the resources of the generation device 51 for a certain period of time. The reserved resources include, for example, the first communication unit 15 of the generation device 51 and the second communication units 25 of the utilization devices 61A and 61B. A network connecting the generation device 51 and the utilization devices 61A and 61B may also be reserved. A time synchronization device (not shown) for synchronizing time may also be reserved.

[0043] By the first reservation unit 14 reserving each of the above-mentioned resources, even if an access such as a quantum entanglement generation request occurs from another communication device, the reserved resources cannot be used.

[0044] In step S17, the transmitting device using device 61A transmits time synchronization information to the generating device 51 to synchronize the time.

[0045] In step S18, the generator 51 generates quantum entangled light and transmits it to each of the utilization devices 61 A and 61 B. As a result, quantum entanglement can be shared between the generator 51 and each of the utilization devices 61 A and 61 B.

[0046] As described above, the communication system E1 according to this embodiment is a communication system E1 that performs quantum entanglement communication between a generating device 51 that generates quantum entanglement and utilization devices 61A and 61B that utilize quantum entanglement via a network, and the generating device 51 includes a first access control unit 12 that authenticates the utilization devices 61A and 61B, a first communication unit 15 that performs quantum entanglement communication with the utilization devices 61A and 61B, and a first reservation unit 14 that reserves resources of the utilization devices 61A and 61B when performing quantum entanglement communication via the first communication unit 15. The utilization devices 61A and 61B include a second access control unit 22 that authenticates the generating device 51, a second communication unit 25 that performs quantum entanglement communication with the generating device 51, and a second reservation unit 24 that reserves resources of the generating device 51 when performing quantum entanglement communication via the second communication unit 25. The first reservation unit 14 prohibits access by any device other than the utilization devices 61A and 61B during the period reserved by the first reservation unit 14, and the second reservation unit 24 prohibits access by any device other than the generation device 51 during the period reserved by the second reservation unit 24.

[0047] In this embodiment, when quantum entanglement communication is performed in the second communication unit 25 of the utilization device 61B, if a user performs a reservation operation, the resources of the generation device 51 and the utilization devices 61A and 61B are reserved and access by other communication devices is prohibited. Therefore, when sharing quantum entanglement, it is possible to avoid the influence of other communication devices. Therefore, it is possible to reliably perform quantum entanglement communication between the quantum entanglement generation device (generation device 51) and the quantum entanglement utilization devices (utilization devices 61A and 61B).

[0048] [Description of Second Embodiment] Next, a second embodiment will be described. Fig. 4 is a block diagram showing the configuration of a communication system E2 according to the second embodiment. The communication system E2 includes a generating device 52 and utilization devices 62A and 62B.

[0049] The communication system E2 according to the second embodiment differs from the communication system E1 shown in FIG. 2 in that the generating device 52 is equipped with a first evaluation unit 16, and the utilization devices 62A and 62B are equipped with a second evaluation unit 26.

[0050] The first evaluation unit 16 generates test quantum entangled light (hereinafter referred to as "test entangled light") and performs quantum entangled communication using the test entangled light (hereinafter referred to as "test entangled communication") to evaluate communication quality before performing quantum entangled communication by the first communication unit 15. The first evaluation unit 16 generates the test entangled light by changing various communication conditions. The communication conditions include, for example, the wavelength of the quantum entangled light, the number of photons, and the frequency of the quantum bit.

[0051] The first evaluation unit 16 evaluates communication quality when test entangled communication using test entangled light is performed by the first communication unit 15 or the second communication unit 25. The first evaluation unit 16 calculates parameters for performing optimal quantum entangled communication based on the evaluation result of the test entangled communication.

[0052] That is, the first communication unit 15 and the second communication unit 25 each have variations in their characteristics. For example, variations occur in the dark count, jitter, detection efficiency, and the like of the photon detector. The first evaluation unit 16 takes into account the effects of these variations and calculates parameters for performing optimal quantum entanglement communication. The first evaluation unit 16 outputs the calculated parameters to the first communication unit 15. The first communication unit 15 uses the parameters set by the first evaluation unit 16 to perform quantum entanglement communication with the utilization devices 62A and 62B.

[0053] In order to extract the parameters, test photons may be transmitted and the dark count, jitter, and detection efficiency may be measured. Furthermore, in order to reduce the variation in parameters between the utilization devices 61A and 61B, the optical level and transmission pulse width transmitted from the first communication unit 25 may be changed in accordance with the characteristics of the second communication unit 25, and the quantum entangled light may be transmitted so as to avoid differences in detection between the utilization devices 61A and 61B.

[0054] That is, the first evaluation unit 16 evaluates the communication quality of the test entangled light when the test entangled light set under a plurality of quantum entanglement conditions is transmitted from the second communication unit 25 to the first communication unit 15. Furthermore, the first evaluation unit 16 feeds back the evaluation result of the communication quality to the utilization devices 62A, 62B, and the second communication unit 25 performs quantum entanglement communication by setting quantum entanglement conditions that make the communication quality higher than a predetermined reference value based on the evaluation result of the communication quality.

[0055] Similarly to the first evaluation unit 16 described above, the second evaluation unit 26 provided in the utilization device 62A evaluates communication quality when test entangled communication is performed using test entangled light by the first communication unit 15 or the second communication unit 25. The second evaluation unit 26 calculates parameters for performing optimal quantum entangled communication based on the evaluation result of the test entangled communication.

[0056] That is, the second evaluation unit 26 evaluates the communication quality of the test entangled light when the test entangled light set under a plurality of quantum entanglement conditions is transmitted from the first communication unit 15 to the second communication unit 25. Furthermore, the second evaluation unit 26 feeds back the evaluation result of the communication quality to the generation device 52, and the second communication unit 25 performs quantum entanglement communication by setting quantum entanglement conditions that make the communication quality higher than a predetermined reference value based on the evaluation result of the communication quality.

[0057] The first evaluation unit 16 and the second evaluation unit 26 do not have to be installed in the generation device 52 and the utilization devices 62A and 62B, respectively. For example, they may be provided in either one of the generation device 52 and the utilization devices 62A and 62B.

[0058] The quality evaluation by the first evaluation unit 16 and the second evaluation unit 26 may be performed before quantum entanglement communication is performed between the first communication unit 15 and the second communication unit 25. Furthermore, the quality evaluation may be performed, for example, at regular time intervals, rather than just before communication. During communication for quality evaluation, wavelength multiplexing or spatial multiplexing may be performed to evaluate the quantum entangled light for testing, or information for communication and testing may be separated and sent for each basis of the same quantum bit.

[0059] Next, the processing procedure of the communication system E2 according to the second embodiment will be described with reference to the flowchart shown in Fig. 5. First, in step S31 of Fig. 5, the first evaluation unit 16 of the generation device 52 generates test entangled light. The first evaluation unit 16 sets the number of photons and the quantum bit frequency of the test entangled light. The first communication unit 15 transmits the test entangled light to the utilization devices 62A and 62B.

[0060] In step S32, the second communication units 25 of the utilization devices 62A and 62B receive the quantum entangled light. The second evaluation unit 26 measures the quantum entanglement in the quantum entangled light received by the second communication unit 25. Time information is shared between the utilization devices 62A and 62B via the classical communication unit 23, and the quality of the quantum entangled light is evaluated. For example, the second evaluation unit 26 detects photons of the quantum entangled light, and performs inter-symbol error rate, dark count rate, photon count number measurement, HOM measurement, interference fringe measurement, and coincidence measurement to evaluate fidelity, quantum state tomography, etc.

[0061] In step S33, the second evaluation unit 26 determines whether the quality of the quantum entanglement communication exceeds a predetermined reference value based on the result of the quality evaluation. If the quality exceeds the reference value (S33; YES), the process proceeds to step S37. If not (S33; NO), the process proceeds to step S34.

[0062] In step S34, the communication control unit 21 of the utilization device 62A requests the communication control unit 11 of the generation device 52 to change the conditions of the test entangled light.

[0063] In step S35, the communication control unit 11 determines whether the conditions can be changed. If the conditions can be changed (S35; YES), the process proceeds to step S36. If not (S35; NO), the process ends.

[0064] In step S36, the first evaluation unit 16 changes the wavelength of the test entangled light, the number of photons, and the frequency of the quantum bit, and then returns the process to step S31.

[0065] In step S37, the first communication unit 15 sets the number of photons and quantum bits of quantum entangled light with high quality. This makes it possible to generate high-quality quantum entangled light. Thereafter, quantum entanglement communication is performed using the same processing procedure as in the first embodiment.

[0066] As described above, the processes of steps S31 to S37 may be performed at any time interval, not just before executing quantum entanglement communication. In the above example, the generating device 52 requests the quantum entanglement evaluation, but the utilization devices 62A and 62B may request the quantum entanglement evaluation.

[0067] The first evaluation unit 16 may change the wavelength, the number of photons, and the frequency of the quantum bit of the test entangled light randomly, or may change them in a predetermined order.

[0068] In this way, in the communication system E2 according to the second embodiment, the quality of quantum entangled light is evaluated by the first evaluation unit 16 installed in the generation device 52 or the second evaluation unit 26 installed in the utilization devices 62A and 62B. The first communication unit 15 and the second communication unit 25 perform quantum entanglement communication using quantum entangled light whose quality exceeds a predetermined reference value. Therefore, it is possible to set a high-quality wavelength, photon number, and quantum bit frequency, thereby enabling high-quality quantum entanglement communication. Furthermore, it is possible to reduce the influence of noise and maintain a stable communication state.

[0069] [Description of Third Embodiment] Next, a third embodiment will be described. Fig. 6 is a block diagram showing the configuration of a communication system E3 according to the third embodiment. The communication system E3 includes a generating device 53, utilization devices 63A and 63B, and an external device 70.

[0070] The communication system E3 according to the third embodiment differs from the communication system E2 shown in FIG. 4 in that the generation device 53 does not have a first reservation unit 14, the utilization devices 63A and 63B do not have a second reservation unit 24, and the classical communication units 13 and 23 of the generation device 53 and utilization devices 63A and 63B are each connected to an external device 70 via a network. The generation device 53 also differs in that it has a first measurement unit 17, and the utilization devices 63A and 63B have a second measurement unit 27. The remaining configuration is the same as that of the communication system E2 shown in FIG. 4.

[0071] The first measurement unit 17 of the generation device 53 measures the quality when the above-mentioned test entangled communication is executed, and transmits the measurement result by classical communication to the third evaluation unit 32 provided in the external device 70. Alternatively, the second measurement unit 27 of the utilization devices 63A and 63B may measure the quality when the test entangled communication is executed, and transmit the measurement result to the third evaluation unit 32 by classical communication.

[0072] The external device 70 includes a third reservation unit 31 and a third evaluation unit 32. The third reservation unit 31 has the same functions as the first reservation unit 14 and the second reservation unit 24 shown in Fig. 2. The external device 70 includes the third reservation unit 31 instead of the first reservation unit 14 and the second reservation unit 24 described above. That is, when a reservation operation is performed, the third reservation unit 31 reserves the resources of the first communication unit 15 and the second communication unit 25, thereby performing control to prohibit other communication units from accessing the generation device 53 and the utilization devices 63A and 63B during the reserved period.

[0073] The third evaluation unit 32 has the same functions as the first evaluation unit 16 and the second evaluation unit 26 shown in Fig. 4. That is, the third evaluation unit 32 acquires the quality from the first measurement unit 17 and the second measurement unit 27 when the first communication unit 15 performs test entangled communication using test entangled light, and evaluates the state of the communication. The third evaluation unit 32 calculates parameters for performing optimal quantum entangled communication based on the evaluation result of the test entangled communication.

[0074] The communication system E3 according to the third embodiment can also achieve the same effects as the communication system E2 according to the second embodiment. Furthermore, in the third embodiment, by installing the third reservation unit 31 and the third evaluation unit 32 in the external device 70, it is possible to simplify the configurations of the generation device 53 and the utilization devices 63A and 63B.

[0075] [Description of Fourth Embodiment] Next, a communication system according to a fourth embodiment will be described. In the first to third embodiments described above, an example in which there is one generator that generates quantum entanglement has been described. However, when there is one generator, if multiple utilization devices issue requests to generate quantum entanglement in the same time period, it is not possible to respond to each of the requests.

[0076] In the communication system E4 according to the fourth embodiment, as shown in FIG. 7, by connecting a plurality of generating devices 50-1 to 50-n and a plurality of using devices 60-1 to 60-m to a network NW, even if a plurality of using devices 60 request quantum entanglement in the same time period, each generating device 50 can respond.

[0077] The utilization device 60 sets various conditions for quantum entanglement, such as wavelength, frequency, entanglement method, and data size, and requests the generation of quantum entanglement from multiple generation devices 50. The generation devices 50 that can meet the above conditions respond to the utilization device 60.

[0078] When the utilization device 60 receives responses from multiple generators 50, it selects one of the generators 50. The utilization device 60 selects the generator 50 that can provide higher quality quantum entanglement communication from the multiple generators 50 (50-1 to 50-n) based on at least one of the conditions of fiber length, entanglement method, wavelength, and fidelity. For example, it selects the generator 50 with the shortest fiber length.

[0079] That is, multiple generating devices 50 are connected to the network NW, and the utilization device 60 selects one of the multiple generating devices 50 to be the target of quantum entanglement communication based on at least one of the conditions of fiber length, entanglement method, wavelength, and fidelity.

[0080] In this way, in the communication system E4 of the fourth embodiment, multiple generating devices 50 are connected to the network NW, so that quantum entanglement communication can be performed even if multiple utilization devices 60 request quantum entanglement at the same time.

[0081] Furthermore, when one generation device 50 fails, quantum entangled light may be received from another generation device 50 as a redundant facility.

[0082] The second reservation unit 24 (see FIGS. 2 and 4) mounted on the utilization device 60 shown in Fig. 7 may search for each generation device 50 (50-1 to 50-n) using conditions such as fiber length, entanglement method, wavelength, and fidelity, and select the generation device 50 capable of quantum entanglement communication of the highest quality. In addition, in the network NW shown in Fig. 7, the reservation unit and evaluation unit may be provided in the external device 70 as shown in Fig. 6.

[0083] [Description of Fifth Embodiment] Next, a communication system according to a fifth embodiment will be described. Fig. 8 is a block diagram showing the configuration of a communication system E5 according to the fifth embodiment. As shown in Fig. 8, the communication system E5 according to the fifth embodiment has a network NW to which a plurality of generating devices 50 (50-1 to 50-4) and a plurality of utilization devices 60 (60-1 to 60-4) are connected, and which is further connected to a plurality of repeater devices 80 (80-1, 80-2) that repeat quantum entangled light.

[0084] Diamond, rare earth crystal, ion trap, etc. can be used as the relay device 80. By connecting the relay devices 80, multiple paths for connecting the production device 50 and the utilization device 60 can be set.

[0085] The utilization device 60 selects a route to the generation device 50. The route selection algorithm is based on the number of repeaters 80, the number of generation devices 50, the fiber length, the entanglement method, the wavelength, and the fidelity. The search may be performed using additional conditions such as the conversion efficiency and storage time of the repeater device 80. In the network NW shown in FIG. 8, the reservation unit and evaluation unit may be provided in the external device 70 as shown in FIG. 6.

[0086] In this way, in the communication system E5 of the fifth embodiment, a relay device 80 is installed in the network NW, so that multiple routes can be searched in a short time, and a high-quality generating device 50 can be selected to perform quantum entanglement communication between the utilization device 60 and the generating device 50.

[0087] The generating device 51 and the utilization devices 61A and 61B installed in the communication system of the present embodiment described above can be, for example, a general-purpose computer system including a CPU (Central Processing Unit, processor) 901, a memory 902, a storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), a communication device 904, an input device 905, and an output device 906, as shown in FIG. 9 . The memory 902 and the storage 903 are storage devices. In this computer system, the CPU 901 executes a predetermined program loaded on the memory 902, thereby realizing the functions of the generating device 51 and the utilization devices 61A and 61B.

[0088] The generating device 51 and the utilization devices 61A and 61B may be implemented by a single computer or by multiple computers. Also, the generating device 51 and the utilization devices 61A and 61B may be virtual machines implemented on a computer.

[0089] The programs for the generating device 51 and the utilizing devices 61A and 61B can be stored in a computer-readable recording medium such as an HDD, an SSD, a Universal Serial Bus (USB) memory, a Compact Disc (CD), or a Digital Versatile Disc (DVD), or can be distributed via a network. The computer-readable recording medium is, for example, a non-transitory recording medium.

[0090] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the present disclosure.

[0091] REFERENCE SIGNS LIST 11 Communication control unit 12 First access control unit 13 Classical communication unit 14 First reservation unit 15 First communication unit 16 First evaluation unit 17 First measurement unit 21 Communication control unit 22 Second access control unit 23 Classical communication unit 24 Second reservation unit 25 Second communication unit 26 Second evaluation unit 27 Second measurement unit 31 Third reservation unit 32 Third evaluation unit 50, 51, 52, 53 Generation device 60, 61A, 61B, 62A, 62B, 63A, 63B Usage device 70 External device 80 Relay device E1, E2, E3, E4, E5 Communication system NW Network

Claims

1. A sharing system that shares quantum entanglement between a generating device that generates quantum entanglement and a utilization device that uses the said quantum entanglement, via a network, The generating apparatus is The system comprises a first access control unit for authenticating with the user device, a first sharing unit for performing quantum entanglement sharing with the user device, and a first reservation unit for reserving resources of the user device when the first sharing unit performs quantum entanglement sharing. The aforementioned device is The system comprises: a second access control unit for authentication with the generation device; a second sharing unit for quantum entanglement sharing with the generation device; and a second reservation unit for reserving resources of the generation device when quantum entanglement sharing is performed by the second sharing unit. A shared system.

2. The first reservation unit prohibits access to devices other than the aforementioned user device during the period reserved by the first reservation unit, and the second reservation unit prohibits access to devices other than the aforementioned generation device during the period reserved by the second reservation unit. The shared system according to claim 1.

3. The second shared unit transmits test entangled light set to the quantum entanglement condition to the first shared unit. The generation apparatus includes a first evaluation unit for evaluating the communication quality of the entangled light used for testing, The first evaluation unit feeds back the evaluation results of the communication quality to the user device. The second sharing unit performs quantum entanglement sharing by setting quantum entanglement conditions that result in higher communication quality than a predetermined standard value, based on the evaluation results of the communication quality. The shared system according to claim 1 or 2.

4. The first shared unit transmits test entangled light set to the quantum entanglement condition to the second shared unit. The aforementioned device includes a second evaluation unit for evaluating the communication quality of the entangled light used for testing, The second evaluation unit feeds back the evaluation results of the communication quality to the generation device. The first sharing unit performs quantum entanglement sharing by setting quantum entanglement conditions that result in higher communication quality than a predetermined standard value, based on the evaluation results of the communication quality. The shared system according to claim 1 or 2.

5. A method for sharing quantum entanglement between a generating device that generates quantum entanglement and a utilization device that utilizes said quantum entanglement, via a network, When quantum entanglement sharing is performed between the first sharing section provided in the generating device and the second sharing section provided in the utilization device, The first reservation unit provided in the generating device reserves the resources of the utilization device, The second reservation unit provided in the aforementioned utilization device reserves the resources of the aforementioned generation device. How to share.

6. A sharing method comprising: the first reservation unit prohibits access to devices other than the user device during the period reserved by the first reservation unit; and the second reservation unit prohibits access to devices other than the generation device during the period reserved by the second reservation unit.

7. A program that causes a computer to function as a generating device provided in the shared system described in claim 1.

8. A program that causes a computer to function as a user device provided in the shared system described in claim 1.