Method and apparatus for performing entanglement-based quantum communication protocol having arbiter without quantum memory

Abstract

A method performed by a first device according to an embodiment of the present specification comprises the steps of: measuring first entanglement photons based on entanglement photon pairs; determining first measurement values based on the same bases as second bases among first measurement values for the first entanglement photons; and transmitting a message to a second device. The message is generated on the basis of the determined first measurement values and message information of the first device.

Description

Method and device for performing an entanglement-based quantum communication protocol with a mediator without quantum memory

[0001] The present specification relates to a method and a device for performing an entanglement-based quantum communication protocol with an arbitrator without quantum memory.

[0002] Mobile communication systems were developed to provide voice services while ensuring user activity. However, they have expanded beyond voice to include data services. Currently, explosive growth in traffic is leading to resource shortages and users are demanding faster services, necessitating a more advanced mobile communication system.

[0003] Next-generation mobile communication systems must support explosive data traffic growth, dramatically increasing data rates per user, a vastly increased number of connected devices, ultra-low end-to-end latency, and high energy efficiency. To achieve these goals, various technologies are being studied, including dual connectivity, massive multiple input multiple output (MIMO), in-band full duplex, non-orthogonal multiple access (NOMA), super wideband support, and device networking.

[0004] Meanwhile, quantum communication techniques involving arbitrators require quantum memory to verify the quantum bit error rate (QBER). Currently, no practical quantum memory has been developed, and long optical cables are used to perform the same function, but this has the disadvantage of causing optical loss.

[0005] The purpose of this specification is to propose a method for performing quantum communication protocols without quantum memory.

[0006] The technical problems to be achieved in this specification are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which this specification pertains from the description below.

[0007] A method performed by a first device in a wireless communication system according to one embodiment of the present disclosure includes the steps of measuring first entangled photons based on entanglement photon pairs, transmitting first measurement information related to a Quantum Bit Error Rate (QBER) check to a third device, receiving information from the third device about whether a process based on the entangled photon pairs is to proceed, receiving information about second basis related to the measurement of the second device from a second device based on the continuation of the process, determining first measurement values ​​based on the same basis as the second basis among first measurement values ​​for the first entangled photons, and transmitting a message to the second device. Whether the process based on the entangled photon pairs is to proceed is determined based on the QBER check. The message is characterized in that it is generated based on the determined first measurement values ​​and message information of the first device.

[0008] The measurement of the first entangled photons can be performed based on single photon detection.

[0009] The first device may be Alice or Bob in the quantum communication system. The second device may be Bob or Alice in the quantum communication system.

[0010] The method may further include a step of receiving information related to the QBER check from the third device. The information related to the QBER check may indicate entangled photon pairs for the QBER check among the entangled photon pairs.

[0011] QBER can be determined based on the first measurement information and the second measurement information transmitted from the second device to the third device.

[0012] The first measurement information may include i) first measurement values ​​selected for the QBER test among the first measurement values ​​and ii) bases related to the selected first measurement values.

[0013] The second measurement information may include i) second measurement values ​​selected for the QBER check among second measurement values ​​for second entangled photons received by the second device, and ii) basis values ​​associated with the selected second measurement values.

[0014] Based on the above QBER being greater than the set value: the process may be aborted.

[0015] Based on the above QBER being less than or equal to a set value: information about first bases related to the remaining first measurement values ​​excluding the selected first measurement values ​​among the first measurement values ​​may be transmitted from the first device to the second device. Information about second bases related to the remaining second measurement values ​​excluding the selected second measurement values ​​among the second measurement values ​​may be transmitted from the second device to the first device.

[0016] The above message can be generated based on the sum of the determined first measurement values ​​and the message information.

[0017] Among the second measurement values, second measurement values ​​based on the same basis as the first basis can be determined. Based on i) an initial state associated with the entangled photon pairs, ii) the determined second measurement values, and iii) basis associated with the determined second measurement values, the message information can be estimated from the message.

[0018] A first device according to another embodiment of the present disclosure includes one or more transceivers, one or more processors, and one or more memories connected to the one or more processors and storing instructions.

[0019] The instructions are characterized in that, based on being executed by the one or more processors, the one or more processors are set to perform all steps of any one of the methods.

[0020] In another embodiment of the present disclosure, one or more non-transitory computer-readable media store instructions, the instructions being executable by one or more processors, characterized in that they cause the one or more processors to perform all steps of any one of the methods.

[0021] In another embodiment of the present disclosure, a method performed by a third device in a wireless communication system includes the steps of transmitting first entanglement photon pairs and second entanglement photon pairs based on entanglement photon pairs to a first device and a second device, respectively; transmitting information related to a quantum bit error rate (QBER) check to the first device and the second device; receiving first measurement information related to the QBER check from the first device; receiving second measurement information related to the QBER check from the second device; performing the QBER check based on the first measurement information and the second measurement information; transmitting information on whether a process based on the entanglement photon pairs is to proceed to the first device and the second device; and transmitting information on an initial state related to the entanglement photon pairs to the first device and the second device. The information related to the QBER check indicates entanglement photon pairs for the QBER check among the entanglement photon pairs. Based on the above QBER check, it is determined whether the process based on the above entangled photon pairs can proceed.

[0022] QBER can be determined based on the first measurement information and the second measurement information.

[0023] Based on the above QBER being greater than the set value: the process may be aborted.

[0024] Based on the above QBER being less than or equal to the set value: information about the initial state of the entangled photon pairs can be transmitted to the first device and the second device.

[0025] The first measurement information may include i) first measurement values ​​selected for the QBER check among the first measurement values ​​for the first entangled photons, and ii) basis values ​​associated with the selected first measurement values.

[0026] The second measurement information may include i) second measurement values ​​selected for the QBER check among the second measurement values ​​for the second entangled photons, and ii) basis values ​​associated with the selected second measurement values.

[0027] In another embodiment of the present disclosure, a method performed by a second device in a wireless communication system includes the steps of measuring second entangled photons based on entanglement photon pairs, transmitting second measurement information related to a Quantum Bit Error Rate (QBER) check to a third device, receiving information from the third device about whether a process based on the entanglement photon pairs is to proceed, receiving information about first bases related to the measurement of the first device from the first device based on the continuation of the process, determining second measurement values ​​based on the same bases as the first bases among second measurement values ​​for the second entangled photons, and receiving a message from the first device.

[0028] Based on the above QBER test, it can be determined whether to proceed with the above process.

[0029] Based on the initial state associated with the entangled photon pairs and the determined second measurement values, message information of the first device is estimated from the message.

[0030] The measurement of the second entangled photons can be performed based on single photon detection.

[0031] QBER can be determined based on the first measurement information and the second measurement information transmitted from the first device to the third device.

[0032] The first measurement information may include i) first measurement values ​​selected for the QBER check among the first measurement values ​​for the first entangled photons received by the first device, and ii) basis values ​​associated with the selected first measurement values.

[0033] The second measurement information may include i) second measurement values ​​selected for the QBER test among the second measurement values ​​and ii) bases related to the selected second measurement values.

[0034] Based on the above QBER being greater than a set value: the process based on the above entangled photon pairs can be stopped.

[0035] Based on the above QBER being less than or equal to a set value: information about first bases related to the remaining first measurement values ​​excluding the selected first measurement values ​​among the first measurement values ​​may be transmitted from the first device to the second device. Information about second bases related to the remaining second measurement values ​​excluding the selected second measurement values ​​among the second measurement values ​​may be transmitted from the second device to the first device.

[0036] The message information can be estimated from the message based on i) the initial state of the entangled photons, ii) the determined second measurement values, and iii) basis values ​​associated with the determined second measurement values.

[0037] The above message may be generated based on i) first measurement values ​​based on the same bases as the second bases among the first measurement values ​​and ii) the sum of the message information.

[0038] According to embodiments of the present specification, quantum communication is performed without quantum memory. Therefore, the implementation complexity of quantum communication can be reduced.

[0039] Additionally, since no other components (e.g., optical cables) are required to replace the quantum memory, additional optical loss can be prevented. Minimizing optical loss can increase communication distance.

[0040] Furthermore, all devices except those sharing entangled photon pairs can act as either transmitters or receivers. This can enhance flexibility in the direction of quantum information transmission and reception compared to conventional processes where specific devices act solely as transmitters or receivers.

[0041] The effects that can be obtained from this specification are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the technical field to which this specification belongs from the description below.

[0042] The accompanying drawings are intended to aid understanding of the present specification and may provide embodiments of the present specification along with detailed descriptions. However, the technical features of the present specification are not limited to specific drawings, and the features disclosed in each drawing may be combined with each other to form new embodiments. Reference numerals in each drawing may indicate structural elements.

[0043] Figure 1 is a drawing showing an example of a communication system applicable to this specification.

[0044] Figure 2 is a drawing showing an example of a wireless device applicable to this specification.

[0045] FIG. 3 is a diagram illustrating a method for processing a transmission signal applicable to the present specification.

[0046] FIG. 4 is a drawing showing another example of a wireless device applicable to this specification.

[0047] FIG. 5 is a drawing showing an example of a mobile device applicable to this specification.

[0048] Figure 6 is a diagram showing physical channels applicable to this specification and a signal transmission method using them.

[0049] Figure 7 is a diagram showing the structure of a wireless frame applicable to this specification.

[0050] Figure 8 is a drawing showing a slot structure applicable to this specification.

[0051] FIG. 9 is a diagram showing an example of a communication structure that can be provided in a 6G system applicable to this specification.

[0052] Figure 10 is a diagram showing the basic properties of quantum information.

[0053] Figure 11 is a schematic diagram of a quantum transmission protocol using photons.

[0054] Figure 12 is a diagram illustrating superdense coding.

[0055] Fig. 13 is a diagram illustrating the structure of a quantum communication technique according to an embodiment of the present specification.

[0056] FIG. 14 is a drawing for explaining the operation according to the structure of a quantum communication technique according to an embodiment of the present specification.

[0057] FIG. 15 is a flowchart illustrating a method performed by a first device according to one embodiment of the present specification.

[0058] FIG. 16 is a flowchart illustrating a method performed by a second device according to another embodiment of the present specification.

[0059] FIG. 17 is a flowchart illustrating a method performed by a third device according to another embodiment of the present specification.

[0060] The following embodiments combine the components and features of this specification in a predetermined form. Each component or feature may be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, some components and / or features may be combined to form embodiments of this specification. The order of operations described in the embodiments of this specification may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.

[0061] In the description of the drawings, procedures or steps that may obscure the gist of the present specification are not described, and procedures or steps that can be understood by a person skilled in the art are also not described.

[0062] Throughout the specification, when a part is said to "comprising" (or including) a certain component, this does not mean that other components are excluded, but rather that other components can be included, unless specifically stated otherwise. In addition, terms such as "...part," "...unit," and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of hardware and software. In addition, the words "a" or "an," "one," "the," and similar related words may be used in the context of describing this specification (especially in the context of the claims below) to include both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context.

[0063] The embodiments of this specification have been described with a focus on the data transmission and reception relationship between a base station and a mobile station. Here, the base station is understood as a terminal node of a network that directly communicates with the mobile station. Certain operations described herein as being performed by the base station may, in some cases, be performed by an upper node of the base station.

[0064] That is, in a network consisting of multiple network nodes including a base station, various operations performed for communication with a mobile station may be performed by the base station or other network nodes other than the base station. In this case, the term 'base station' may be replaced by terms such as fixed station, Node B, eNB (eNode B), gNB (gNode B), ng-eNB, advanced base station (ABS), or access point.

[0065] Additionally, in the embodiments of the present specification, the term terminal may be replaced with terms such as user equipment (UE), mobile station (MS), subscriber station (SS), mobile subscriber station (MSS), mobile terminal, or advanced mobile station (AMS).

[0066] Additionally, a transmitter refers to a fixed and / or mobile node that provides data or voice services, and a receiver refers to a fixed and / or mobile node that receives data or voice services. Therefore, for uplink, a mobile station can be the transmitter, and a base station can be the receiver. Similarly, for downlink, a mobile station can be the receiver, and a base station can be the transmitter.

[0067] Embodiments of the present specification may be supported by standard documents disclosed in at least one of wireless access systems, such as IEEE 802.xx system, 3rd Generation Partnership Project (3GPP) system, 3GPP Long Term Evolution (LTE) system, 3GPP 5G (5th generation) NR (New Radio) system and 3GPP2 system, and in particular, embodiments of the present specification may be supported by 3GPP TS (technical specification) 38.211, 3GPP TS 38.212, 3GPP TS 38.213, 3GPP TS 38.321 and 3GPP TS 38.331 documents.

[0068] Furthermore, the embodiments of this specification may be applied to other wireless access systems and are not limited to the aforementioned systems. For example, they may also be applicable to systems implemented after the 3GPP 5G NR system, and are not limited to a specific system.

[0069] That is, obvious steps or parts not described in the embodiments of this specification may be explained by reference to the above documents. In addition, all terms disclosed in this specification may be explained by the above standard documents.

[0070] Hereinafter, preferred embodiments according to the present specification will be described in detail with reference to the accompanying drawings. The detailed description set forth below, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the present specification and is not intended to represent the only embodiments in which the technical components of the present specification may be implemented.

[0071] Additionally, specific terms used in the embodiments of this specification are provided to aid in understanding of this specification, and the use of these specific terms may be changed to other forms without departing from the technical spirit of this specification.

[0072] The following technology can be applied to various wireless access systems such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access).

[0073] In order to make the following description clear, the following description is based on a 3GPP communication system (e.g., LTE, NR, etc.), but the technical idea of ​​the present invention is not limited thereto. LTE may refer to technology after 3GPP TS 36.xxx Release 8. Specifically, LTE technology after 3GPP TS 36.xxx Release 10 may be referred to as LTE-A, and LTE technology after 3GPP TS 36.xxx Release 13 may be referred to as LTE-A pro. 3GPP NR may refer to technology after TS 38.xxx Release 15. 3GPP 6G may refer to technology after TS Release 17 and / or Release 18. "xxx" refers to a standard document detail number. LTE / NR / 6G may be collectively referred to as a 3GPP system.

[0074] For background information, terms, abbreviations, etc. used in this specification, reference may be made to standard documents published prior to the invention of the present invention. For example, reference may be made to the 36.xxx and 38.xxx standard documents.

[0075] Communication systems applicable to this specification

[0076] Although not limited thereto, the various descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed herein may be applied to various fields requiring wireless communication / connectivity (e.g., 5G) between devices.

[0077] Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings / descriptions below, the same drawing reference numerals may represent identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

[0078] FIG. 1 is a diagram illustrating an example of a communication system applicable to the present specification. Referring to FIG. 1, a communication system (100) applicable to the present specification includes a wireless device, a base station, and a network. Here, a wireless device refers to a device that performs communication using a wireless access technology (e.g., 5G NR, LTE) and may be referred to as a communication / wireless / 5G device. Although not limited thereto, the wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an XR (extended reality) device (100c), a hand-held device (100d), a home appliance (100e), an IoT (Internet of Things) device (100f), and an AI (artificial intelligence) device / server (100g). For example, the vehicle may include a vehicle equipped with a wireless communication function, an autonomous vehicle, a vehicle capable of performing vehicle-to-vehicle communication, etc. Here, the vehicles (100b-1, 100b-2) may include unmanned aerial vehicles (UAVs) (e.g., drones). The XR devices (100c) include augmented reality (AR) / virtual reality (VR) / mixed reality (MR) devices, and may be implemented in the form of head-mounted devices (HMDs), head-up displays (HUDs) installed in vehicles, televisions, smartphones, computers, wearable devices, home appliances, digital signage, vehicles, robots, etc. The portable devices (100d) may include smartphones, smart pads, wearable devices (e.g., smartwatches, smart glasses), computers (e.g., laptops, etc.), etc. The home appliances (100e) may include TVs, refrigerators, washing machines, etc. The IoT devices (100f) may include sensors, smart meters, etc.For example, the base station (120) and the network (130) may also be implemented as wireless devices, and a specific wireless device (120a) may act as a base station / network node to other wireless devices.

[0079] Wireless devices (100a to 100f) can be connected to a network (130) via a base station (120). AI technology can be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (100g) via a network (130). The network (130) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, etc. The wireless devices (100a to 100f) can communicate with each other via the base station (120) / network (130), but can also communicate directly (e.g., sidelink communication) without going through the base station (120) / network (130). For example, vehicles (100b-1, 100b-2) can communicate directly (e.g., V2V (vehicle to vehicle) / V2X (vehicle to everything) communication). In addition, IoT devices (100f) (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

[0080] Wireless communication / connection (150a, 150b, 150c) can be established between wireless devices (100a to 100f) / base stations (120), and base stations (120) / base stations (120). Here, the wireless communication / connection can be established through various wireless access technologies (e.g., 5G NR) such as uplink / downlink communication (150a), sidelink communication (150b) (or D2D communication), and communication between base stations (150c) (e.g., relay, IAB (integrated access backhaul)). Through the wireless communication / connection (150a, 150b, 150c), the wireless device and base station / wireless device, and base stations and base stations can transmit / receive wireless signals to / from each other. For example, the wireless communication / connection (150a, 150b, 150c) can transmit / receive signals through various physical channels. To this end, at least some of the various configuration information setting processes for transmitting / receiving wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, resource mapping / demapping, etc.), and resource allocation processes may be performed based on various proposals of this specification.

[0081] Communication systems applicable to this specification

[0082] FIG. 2 is a diagram illustrating an example of a wireless device applicable to this specification.

[0083] Referring to FIG. 2, the first wireless device (200a) and the second wireless device (200b) can transmit and receive wireless signals via various wireless access technologies (e.g., LTE, NR). Here, {the first wireless device (200a), the second wireless device (200b)} can correspond to {the wireless device (100x), the base station (120)} and / or {the wireless device (100x), the wireless device (100x)} of FIG. 1.

[0084] A first wireless device (200a) includes one or more processors (202a) and one or more memories (204a), and may further include one or more transceivers (206a) and / or one or more antennas (208a). The processor (202a) controls the memories (204a) and / or the transceivers (206a), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein. For example, the processor (202a) may process information in the memory (204a) to generate first information / signals, and then transmit a wireless signal including the first information / signals via the transceivers (206a). In addition, the processor (202a) may receive a wireless signal including second information / signals via the transceivers (206a), and then store information obtained from signal processing of the second information / signals in the memory (204a). The memory (204a) may be connected to the processor (202a) and may store various information related to the operation of the processor (202a). For example, the memory (204a) may perform some or all of the processes controlled by the processor (202a), or may store software code including instructions for performing the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein. Here, the processor (202a) and the memory (204a) may be part of a communication modem / circuit / chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206a) may be connected to the processor (202a) and may transmit and / or receive wireless signals via one or more antennas (208a). The transceiver (206a) may include a transmitter and / or a receiver. The transceiver (206a) may be used interchangeably with an RF (radio frequency) unit. In this specification, wireless device may also mean a communication modem / circuit / chip.

[0085] The second wireless device (200b) includes one or more processors (202b), one or more memories (204b), and may further include one or more transceivers (206b) and / or one or more antennas (208b). The processor (202b) controls the memories (204b) and / or the transceivers (206b), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein. For example, the processor (202b) may process information in the memory (204b) to generate third information / signals, and then transmit a wireless signal including the third information / signals via the transceivers (206b). In addition, the processor (202b) may receive a wireless signal including fourth information / signals via the transceivers (206b), and then store information obtained from signal processing of the fourth information / signals in the memory (204b). The memory (204b) may be connected to the processor (202b) and may store various information related to the operation of the processor (202b). For example, the memory (204b) may perform some or all of the processes controlled by the processor (202b), or may store software code including instructions for performing the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein. Here, the processor (202b) and the memory (204b) may be part of a communication modem / circuit / chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206b) may be connected to the processor (202b) and may transmit and / or receive wireless signals via one or more antennas (208b). The transceiver (206b) may include a transmitter and / or a receiver. The transceiver (206b) may be used interchangeably with an RF unit. In this specification, wireless device may also mean a communication modem / circuit / chip.

[0086] Hereinafter, hardware elements of the wireless device (200a, 200b) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (202a, 202b). For example, one or more processors (202a, 202b) may implement one or more layers (e.g., functional layers such as physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), radio resource control (RRC), and service data adaptation protocol (SDAP)). One or more processors (202a, 202b) may generate one or more Protocol Data Units (PDUs) and / or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein. One or more processors (202a, 202b) may generate messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed herein. One or more processors (202a, 202b) may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, procedures, proposals and / or methods disclosed herein and provide the signals to one or more transceivers (206a, 206b). One or more processors (202a, 202b) may receive signals (e.g., baseband signals) from one or more transceivers (206a, 206b) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed herein.

[0087] One or more processors (202a, 202b) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors (202a, 202b) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in one or more processors (202a, 202b). The descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, suggestions, methods and / or operation flowcharts disclosed in this specification may be implemented using firmware or software configured to perform one or more processors (202a, 202b) or stored in one or more memories (204a, 204b) and executed by one or more processors (202a, 202b). The descriptions, functions, procedures, suggestions, methods and / or operation flowcharts disclosed in this specification may be implemented using firmware or software in the form of codes, instructions and / or sets of instructions.

[0088] One or more memories (204a, 204b) may be coupled to one or more processors (202a, 202b) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. The one or more memories (204a, 204b) may be configured as read only memory (ROM), random access memory (RAM), erasable programmable read only memory (EPROM), flash memory, hard drives, registers, cache memory, computer readable storage media, and / or combinations thereof. The one or more memories (204a, 204b) may be located internally and / or externally to the one or more processors (202a, 202b). Additionally, the one or more memories (204a, 204b) may be coupled to the one or more processors (202a, 202b) via various technologies, such as wired or wireless connections.

[0089] One or more transceivers (206a, 206b) can transmit user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or flowcharts of this specification, to one or more other devices. One or more transceivers (206a, 206b) can receive user data, control information, wireless signals / channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and / or flowcharts of this specification, from one or more other devices. For example, one or more transceivers (206a, 206b) can be coupled to one or more processors (202a, 202b) and can transmit and receive wireless signals. For example, one or more processors (202a, 202b) can control one or more transceivers (206a, 206b) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (202a, 202b) may control one or more transceivers (206a, 206b) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (206a, 206b) may be coupled to one or more antennas (208a, 208b), and one or more transceivers (206a, 206b) may be configured to transmit and receive user data, control information, wireless signals / channels, or the like, as referred to in the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein, via one or more antennas (208a, 208b). In the present specification, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (206a, 206b) can convert received user data, control information, wireless signals / channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals / channels, etc. using one or more processors (202a, 202b).One or more transceivers (206a, 206b) may convert user data, control information, wireless signals / channels, etc. processed by one or more processors (202a, 202b) from baseband signals to RF band signals. For this purpose, one or more transceivers (206a, 206b) may include an (analog) oscillator and / or filter.

[0090] FIG. 3 is a diagram illustrating a method for processing a transmission signal applied to the present specification. For example, the transmission signal may be processed by a signal processing circuit. At this time, the signal processing circuit (300) may include a scrambler (310), a modulator (320), a layer mapper (330), a precoder (340), a resource mapper (350), and a signal generator (360). At this time, as an example, the operations / functions of FIG. 3 may be performed in the processors (202a, 202b) and / or the transceivers (206a, 206b) of FIG. 2. Furthermore, as an example, the hardware elements of FIG. 3 may be implemented in the processors (202a, 202b) and / or the transceivers (206a, 206b) of FIG. 2. For example, blocks 310 to 350 may be implemented in the processor (202a, 202b) of FIG. 2, and block 360 may be implemented in the transceiver (206a, 206b) of FIG. 2, and are not limited to the above-described embodiments.

[0091] The codeword can be converted into a wireless signal through the signal processing circuit (300) of FIG. 3. Here, the codeword is an encoded bit sequence of an information block. The information block may include a transport block (e.g., a UL-SCH transport block, a DL-SCH transport block). The wireless signal may be transmitted through various physical channels (e.g., a PUSCH, a PDSCH) of FIG. 6. Specifically, the codeword can be converted into a bit sequence scrambled by a scrambler (310). The scramble sequence used for scrambling is generated based on an initialization value, and the initialization value may include ID information of the wireless device, etc. The scrambled bit sequence can be modulated into a modulation symbol sequence by a modulator (320). The modulation scheme may include pi / 2-binary phase shift keying (pi / 2-BPSK), m-phase shift keying (m-PSK), m-quadrature amplitude modulation (m-QAM), etc.

[0092] A complex modulation symbol sequence can be mapped to one or more transmission layers by a layer mapper (330). The modulation symbols of each transmission layer can be mapped to the corresponding antenna port(s) by a precoder (340) (precoding). The output z of the precoder (340) can be obtained by multiplying the output y of the layer mapper (330) by an N*M precoding matrix W. Here, N is the number of antenna ports, and M is the number of transmission layers. Here, the precoder (340) can perform precoding after performing transform precoding (e.g., discrete Fourier transform (DFT) transform) on the complex modulation symbols. In addition, the precoder (340) can perform precoding without performing transform precoding.

[0093] The resource mapper (350) can map modulation symbols of each antenna port to time-frequency resources. The time-frequency resources can include multiple symbols (e.g., CP-OFDMA symbols, DFT-s-OFDMA symbols) in the time domain and multiple subcarriers in the frequency domain. The signal generator (360) generates a wireless signal from the mapped modulation symbols, and the generated wireless signal can be transmitted to another device through each antenna. To this end, the signal generator (360) can include an inverse fast Fourier transform (IFFT) module, a cyclic prefix (CP) inserter, a digital-to-analog converter (DAC), a frequency uplink converter, and the like.

[0094] The signal processing process for receiving signals in a wireless device can be configured in reverse order of the signal processing process (310-360) of FIG. 3. For example, a wireless device (e.g., 200a, 200b of FIG. 2) can receive wireless signals from the outside through an antenna port / transceiver. The received wireless signals can be converted into baseband signals through a signal restorer. For this purpose, the signal restorer can include a frequency downlink converter, an analog-to-digital converter (ADC), a CP remover, and a fast Fourier transform (FFT) module. Thereafter, the baseband signal can be restored to a codeword through a resource demapper process, a postcoding process, a demodulation process, and a descrambling process. The codewords can be restored to the original information blocks through decoding. Accordingly, a signal processing circuit (not shown) for a received signal may include a signal restorer, a resource de-mapper, a postcoder, a demodulator, a de-scrambler, and a decoder.

[0095] Wireless device structure applicable to this specification

[0096] FIG. 4 is a diagram illustrating another example of a wireless device to which the present specification applies.

[0097] Referring to FIG. 4, the wireless device (400) corresponds to the wireless devices (200a, 200b) of FIG. 2 and may be composed of various elements, components, units, and / or modules. For example, the wireless device (400) may include a communication unit (410), a control unit (420), a memory unit (430), and additional elements (440). The communication unit may include a communication circuit (412) and a transceiver(s) (414). For example, the communication circuit (412) may include one or more processors (202a, 202b) and / or one or more memories (204a, 204b) of FIG. 2. For example, the transceiver(s) (414) may include one or more transceivers (206a, 206b) and / or one or more antennas (208a, 208b) of FIG. 2. The control unit (420) is electrically connected to the communication unit (410), the memory unit (430), and the additional elements (440) and controls the overall operation of the wireless device. For example, the control unit (420) may control the electrical / mechanical operation of the wireless device based on the program / code / command / information stored in the memory unit (430). In addition, the control unit (420) may transmit information stored in the memory unit (430) to an external device (e.g., another communication device) via a wireless / wired interface through the communication unit (410), or store information received from an external device (e.g., another communication device) via a wireless / wired interface in the memory unit (430).

[0098] The additional element (440) may be configured in various ways depending on the type of the wireless device. For example, the additional element (440) may include at least one of a power unit / battery, an input / output unit, a driving unit, and a computing unit. Although not limited thereto, the wireless device (400) may be implemented in the form of a robot (Fig. 1, 100a), a vehicle (Fig. 1, 100b-1, 100b-2), an XR device (Fig. 1, 100c), a portable device (Fig. 1, 100d), a home appliance (Fig. 1, 100e), an IoT device (Fig. 1, 100f), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or a financial device), a security device, a climate / environmental device, an AI server / device (Fig. 1, 140), a base station (Fig. 1, 120), a network node, etc. Wireless devices may be mobile or stationary depending on the use / service.

[0099] In FIG. 4, various elements, components, units / parts, and / or modules within the wireless device (400) may be entirely interconnected via a wired interface, or at least some may be wirelessly connected via a communication unit (410). For example, within the wireless device (400), the control unit (420) and the communication unit (410) may be wired, and the control unit (420) and a first unit (e.g., 430, 440) may be wirelessly connected via the communication unit (410). In addition, each element, component, unit / part, and / or module within the wireless device (400) may further include one or more elements. For example, the control unit (420) may be composed of a set of one or more processors. For example, the control unit (420) may be composed of a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphics processing processor, a memory control processor, etc. As another example, the memory unit (430) may be composed of RAM, DRAM (dynamic RAM), ROM, flash memory, volatile memory, non-volatile memory, and / or a combination thereof.

[0100] Mobile devices to which this specification applies

[0101] FIG. 5 is a drawing illustrating an example of a mobile device to which the present specification applies.

[0102] Figure 5 illustrates an example of a mobile device applicable to the present specification. The mobile device may include a smartphone, a smart pad, a wearable device (e.g., a smart watch, smart glasses), or a portable computer (e.g., a laptop, etc.). The mobile device may be referred to as a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), an advanced mobile station (AMS), or a wireless terminal (WT).

[0103] Referring to FIG. 5, the portable device (500) may include an antenna unit (508), a communication unit (510), a control unit (520), a memory unit (530), a power supply unit (540a), an interface unit (540b), and an input / output unit (540c). The antenna unit (508) may be configured as a part of the communication unit (510). Blocks 510 to 530 / 540a to 540c correspond to blocks 410 to 430 / 440 of FIG. 4, respectively.

[0104] The communication unit (510) can transmit and receive signals (e.g., data, control signals, etc.) with other wireless devices and base stations. The control unit (520) can control components of the portable device (500) to perform various operations. The control unit (520) can include an AP (application processor). The memory unit (530) can store data / parameters / programs / codes / commands required for operating the portable device (500). In addition, the memory unit (530) can store input / output data / information, etc. The power supply unit (540a) supplies power to the portable device (500) and can include a wired / wireless charging circuit, a battery, etc. The interface unit (540b) can support connection between the portable device (500) and other external devices. The interface unit (540b) can include various ports (e.g., audio input / output ports, video input / output ports) for connection with external devices. The input / output unit (540c) can input or output video information / signals, audio information / signals, data, and / or information input from a user. The input / output unit (540c) may include a camera, a microphone, a user input unit, a display unit (540d), a speaker, and / or a haptic module.

[0105] For example, in the case of data communication, the input / output unit (540c) obtains information / signals (e.g., touch, text, voice, image, video) input by the user, and the obtained information / signals can be stored in the memory unit (530). The communication unit (510) can convert the information / signals stored in the memory into wireless signals, and transmit the converted wireless signals directly to other wireless devices or to a base station. In addition, the communication unit (510) can receive wireless signals from other wireless devices or base stations, and then restore the received wireless signals to the original information / signals. The restored information / signals can be stored in the memory unit (530) and then output in various forms (e.g., text, voice, image, video, haptic) through the input / output unit (540c).

[0106] Physical channels and general signal transmission

[0107] In a wireless access system, a terminal can receive information from a base station via the downlink (DL) and transmit it to the base station via the uplink (UL). The information transmitted and received between the base station and the terminal includes general data and various control information, and various physical channels exist depending on the type and purpose of the information being transmitted and received.

[0108] FIG. 6 is a diagram illustrating physical channels applicable to this specification and a signal transmission method using them.

[0109] When a terminal is powered on again from a powered-off state or newly enters a cell, it performs an initial cell search operation, such as synchronizing with the base station, in step S611. To this end, the terminal receives a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) from the base station to synchronize with the base station and obtain information such as the cell ID.

[0110] After that, the terminal can obtain broadcast information within the cell by receiving a physical broadcast channel (PBCH) signal from the base station. Meanwhile, the terminal can check the downlink channel status by receiving a downlink reference signal (DL RS) in the initial cell search phase. After completing the initial cell search, the terminal can obtain more specific system information by receiving a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) based on the physical downlink control channel information in step S612.

[0111] Thereafter, the terminal may perform a random access procedure such as steps S613 to S616 to complete connection to the base station. To this end, the terminal may transmit a preamble through a physical random access channel (PRACH) (S613) and receive a random access response (RAR) for the preamble through a physical downlink control channel and a physical downlink shared channel corresponding thereto (S614). The terminal may transmit a physical uplink shared channel (PUSCH) using scheduling information in the RAR (S615) and perform a contention resolution procedure such as receiving a physical downlink control channel signal and a physical downlink shared channel signal corresponding thereto (S616).

[0112] A terminal that has performed the procedure described above can then perform reception of a physical downlink control channel signal and / or a physical downlink shared channel signal (S617) and transmission of a physical uplink shared channel (PUSCH) signal and / or a physical uplink control channel (PUCCH) signal (S618) as a general uplink / downlink signal transmission procedure.

[0113] Control information transmitted from a terminal to a base station is collectively referred to as uplink control information (UCI). UCI includes hybrid automatic repeat and request acknowledgment / negative ACK (HARQ-ACK / NACK), scheduling request (SR), channel quality indication (CQI), precoding matrix indication (PMI), rank indication (RI), and beam indication (BI) information. UCI is generally transmitted periodically through PUCCH, but depending on the embodiment (e.g., when control information and traffic data must be transmitted simultaneously), it may be transmitted through PUSCH. In addition, the terminal may transmit UCI aperiodically through PUSCH upon request / instruction from the network.

[0114] Figure 7 is a diagram illustrating the structure of a wireless frame applicable to this specification.

[0115] Uplink and downlink transmissions based on the NR system can be based on frames such as those in FIG. 7. At this time, one radio frame has a length of 10 ms and can be defined as two 5 ms half-frames (HF). One half-frame can be defined as five 1 ms subframes (SF). One subframe is divided into one or more slots, and the number of slots within a subframe can depend on the subcarrier spacing (SCS). At this time, each slot can contain 12 or 14 OFDM (A) symbols depending on the cyclic prefix (CP). When a normal CP is used, each slot can contain 14 symbols. When an extended CP is used, each slot can contain 12 symbols. Here, the symbol may include an OFDM symbol (or CP-OFDM symbol), an SC-FDMA symbol (or DFT-s-OFDM symbol).

[0116] Table 1 shows the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS when a general CP is used, and Table 2 shows the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS when an extended CSP is used.

[0117]

[0118]

[0119] In the above Tables 1 and 2, Nslotsymb may represent the number of symbols in a slot, Nframe,μslot may represent the number of slots in a frame, and Nsubframe,μslot may represent the number of slots in a subframe.

[0120] Additionally, in a system to which the present specification is applicable, OFDM(A) numerologies (e.g., SCS, CP length, etc.) may be set differently between multiple cells merged into a single terminal. Accordingly, the (absolute time) interval of a time resource (e.g., SF, slot, or TTI) (conveniently referred to as TU (time unit)) consisting of the same number of symbols may be set differently between the merged cells.

[0121] NR can support multiple numerologies (or subcarrier spacing (SCS)) to support various 5G services. For example, a 15 kHz SCS supports wide areas in traditional cellular bands; a 30 kHz / 60 kHz SCS supports dense urban areas, lower latency, and wider carrier bandwidth; and a 60 kHz or higher SCS can support bandwidths greater than 24.25 GHz to overcome phase noise.

[0122] The NR frequency band is defined by two types of frequency ranges (FR1 and FR2). FR1 and FR2 can be configured as shown in the table below. FR2 can also refer to millimeter wave (mmW).

[0123]

[0124] Additionally, for example, the numerology described above may be set differently in a communication system to which the present specification is applicable. For example, a terahertz wave (THz) band may be used as a frequency band higher than the FR2 described above. In the THz band, the SCS may be set to be larger than in the NR system, and the number of slots may also be set differently, and the present invention is not limited to the above-described embodiment.

[0125] Figure 8 is a drawing illustrating a slot structure applicable to this specification.

[0126] A single slot contains multiple symbols in the time domain. For example, a slot contains seven symbols in a regular CP, but a slot may contain six symbols in an extended CP. A carrier contains multiple subcarriers in the frequency domain. A Resource Block (RB) can be defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain.

[0127] Additionally, a Bandwidth Part (BWP) is defined as multiple consecutive (P)RBs in the frequency domain, and can correspond to one numerology (e.g., SCS, CP length, etc.).

[0128] A carrier can contain up to N (e.g., 5) BWPs. Data communication is performed through an activated BWP, and only one BWP can be activated per terminal. Each element in the resource grid is referred to as a Resource Element (RE), to which a single complex symbol can be mapped.

[0129] 6G communication system

[0130] The 6G (wireless communication) system aims to achieve (i) very high data rates per device, (ii) a very large number of connected devices, (iii) global connectivity, (iv) very low latency, (v) low energy consumption for battery-free IoT devices, (vi) ultra-reliable connectivity, and (vii) connected intelligence with machine learning capabilities. The vision of the 6G system can be divided into four aspects: "intelligent connectivity," "deep connectivity," "holographic connectivity," and "ubiquitous connectivity," and the 6G system can satisfy the requirements as shown in Table 4 below. In other words, Table 4 is a table showing the requirements of the 6G system.

[0131]

[0132] At this time, the 6G system may have key factors such as enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), massive machine type communications (mMTC), AI integrated communication, tactile internet, high throughput, high network capacity, high energy efficiency, low backhaul and access network congestion, and enhanced data security.

[0133] FIG. 9 is a diagram illustrating an example of a communication structure that can be provided in a 6G system applicable to this specification.

[0134] Referring to Figure 9, 6G systems are expected to have 50 times higher simultaneous wireless connectivity than 5G wireless systems. URLLC, a key feature of 5G, is expected to become a more prominent technology in 6G communications by providing end-to-end latency of less than 1 ms. Furthermore, 6G systems will have significantly better volumetric spectral efficiency than the commonly used area spectral efficiency. 6G systems can offer extremely long battery life and advanced battery technologies for energy harvesting, eliminating the need for separate charging for mobile devices in 6G systems. Furthermore, new network characteristics in 6G may include:

[0135] - Satellite integrated network: 6G is expected to integrate with satellites to provide a global mobile network. The integration of terrestrial, satellite, and airborne networks into a single wireless communications system could be crucial for 6G.

[0136] Connected Intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary, upgrading the wireless evolution from "connected objects" to "connected intelligence." AI can be applied at every stage of the communication process (or at every signal processing step, as described below).

[0137] - Seamless integration of wireless information and energy transfer: 6G wireless networks will transfer power to charge the batteries of devices such as smartphones and sensors. Therefore, wireless information and energy transfer (WIET) will be integrated.

[0138] - Ubiquitous super 3-dimension connectivity: Access to networks and core network functions from drones and very low Earth orbit satellites will create super 3-dimension connectivity in 6G ubiquitous.

[0139] Some general requirements for the new network characteristics of 6G, such as the above, may be as follows:

[0140] - Small cell networks: The concept of small cell networks was introduced to improve received signal quality in cellular systems by increasing throughput, energy efficiency, and spectral efficiency. Consequently, small cell networks are essential for 5G and beyond-5G (5GB) communication systems. Accordingly, 6G communication systems also adopt the characteristics of small cell networks.

[0141] Ultra-dense heterogeneous networks: Ultra-dense heterogeneous networks will be another key feature of 6G communication systems. Multi-tier networks comprised of heterogeneous networks improve overall QoS and reduce costs.

[0142] High-capacity backhaul: Backhaul connections are characterized by high-capacity backhaul networks to support high-volume traffic. High-speed fiber optics and free-space optics (FSO) systems may be potential solutions to this problem.

[0143] - Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communications is a key feature of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

[0144] - Softwarization and virtualization: Softwarization and virtualization are two critical features that form the foundation of the design process for 5GB networks to ensure flexibility, reconfigurability, and programmability. Furthermore, billions of devices can be shared on a shared physical infrastructure.

[0145] The above-mentioned content can be applied in combination with the methods proposed in this specification, which will be described later, or can be supplemented to clarify the technical characteristics of the methods proposed in this specification. The methods described below are distinguished for convenience of explanation, and it is understood that certain components of one method may be substituted for or combined with other methods.

[0146] The symbols / abbreviations / terms used in this specification are as follows.

[0147] - QD: Quantum Dialogue

[0148] - QSDC: Quantum Secure Direct Communication

[0149] - CQC: Controlled Quantum Communication

[0150] - QBER: Quantum Bit Error Rate

[0151] - Alice: Sender

[0152] - Bob: Recipient

[0153] This specification relates to a method for implementing an entanglement-based controlled quantum communication (CQC) protocol without quantum memory.

[0154] Below, the background related to the embodiments of this specification is specifically described.

[0155] Entanglement

[0156] Classical computers have internal calculation units, and the basic calculation unit of a computer is a bit, which has two states: 0 and 1. Meanwhile, in quantum mechanics, a single quantum can be in a superposition of multiple states, and quantum computers utilizing this are being studied. The quantum bits used in quantum computers are called qubits (quantum bits) to distinguish them from the bits in classical computers. In other words, a single quantum can be in both a 0 state and a 1 state. However, when a quantum in a superposition state is measured, it collapses into one of the superposition states, determining the state as either 0 or 1.

[0157] Therefore, to represent qubits, a method is needed to represent superposed quantum states. One way to represent quantum states is through Dirac notation. Dirac notation can also be referred to as bra-ket notation.

[0158] A ket can represent a quantum state Ψ, which can be expressed in the form |Ψ〉. A bra represents the complex conjugate transpose of a ket, which can be expressed in the form 〈φ|. Therefore, 〈φ| and |φ〉 form a complex conjugate transpose relationship.

[0159] The inner product between two states can be computed by combining bras and kets. For example, the inner product between two states |Ψ〉 and |φ〉 can be expressed in the form 〈Ψ|φ〉. In addition, all quantum states can be assumed to be normalized. That is, we can define a set of state functions that satisfy 〈Ψ|Ψ〉 = 1. This set is defined as the Hilbert space. In addition, two quantum states that produce a bra-ket result of 0 in the Hilbert space can be defined to be orthogonal. Therefore, if 〈Ψ|φ〉 = 0, the relationship between the |Ψ〉 state and the |φ〉 state is orthogonal to each other.

[0160] Entanglement is a very important property that differentiates quantum systems from classical information. Entanglement refers to a state in which the results of different observations are closely related to each other. The entanglement state of a quantum system acts more strongly than any entanglement state (correlation) that exists in classical mechanics. Two qubits can be represented as a superposition of four fundamental quantum states in Hilbert space. Here, the four fundamental quantum states are . The fundamental quantum state of two qubits can be expressed through tensor operations on the fundamental states of individual qubits. If the state of two qubits cannot be expressed as a tensor product of a single qubit, such a qubit state is called an entangled state. There are four cases, which are representative examples of qubits in an entangled state and are called EPR (Einstein-Podolsky-Rosen) states, and the four cases are as shown in Mathematical Expression 1 below.

[0161]

[0162] The above EPR state is also called the Bell state, and the measurement result of the preceding qubit always affects the measurement of the succeeding qubit. Furthermore, all four of the above pure states are maximally entangled states and constitute the vertical basis of the two-qubit Hilbert Space.

[0163] For entangled qubits with M>2 qubits, the GHZ state is as follows.

[0164]

[0165] When M=2 The Bell State is generally expressed for M = 3. Sometimes, the GHZ State can be expressed by extending it to a system corresponding to d-dimension rather than 2-dimension.

[0166] Figure 10 is a diagram showing the basic properties of quantum information.

[0167] The decay of quantum information by measurement

[0168] Quantum information exists probabilistically, and quantum information collapses into a ground state the moment it is measured and cannot be restored to the state before the measurement. We will explain the measurement of quantum information by the measurement operator in more detail. Quantum information after measurement is a probability and It collapses into one of the states of the basis that constitutes information. The collapsed information does not have the information of 'a' or 'b' and cannot return to the state before measurement.

[0169] From the perspective of quantum error-correcting codes, applying quantum error-correcting codes in quantum information systems requires generating codewords, estimating errors in the channel, and then restoring the information without measuring the information during the encoding and restoration process, or without measurements that would alter the information. In this process, continuously occurring quantum errors are digitized through measurements for error estimation.

[0170] Quantum Teleportation (QT)

[0171] Quantum teleportation is a technology that transmits quantum information from a sender at a specific location to a receiver located a certain distance away. Contrary to the original meaning of the word "teleport," in quantum teleportation, the carriers on both sides are fixed, and the actual carriers are not transmitted, but rather quantum information is transmitted between carriers. This information transmission requires an entangled quantum state, or Bell State, which provides statistical correlation between separate physical systems. Since any change experienced by one of the entangled particles causes the other particle to undergo the same change, the two particles behave as if they were in a single quantum state.

[0172] Figure 11 is a schematic diagram of a quantum transmission protocol using photons.

[0173] Referring to Figure 11, for quantum transmission, resources are required: a classical channel capable of transmitting two classical bits, a Bell State (entanglement state) generation device, a quantum channel for moving two particles in the Bell State to different locations of the transmitting and receiving ends, a Bell State Measurement device at the transmitting end, and a Unitary Operation device at the receiving end. Quantum information to be transmitted The protocol's behavior is as follows:

[0174] [1] Entanglement Generation: Entanglement state of two qubits is created using a Bell State generation device.

[0175] [2] Entanglement Distribution: The generated entanglement state is transferred through a quantum channel, with one qubit transferred to the location of the sender Alice (A) and the other qubit transferred to the location of the receiver Bob (B).

[0176] [3] Quantum Pre-processing: Alice wants to transmit the quantum state And performs Bell State Measurement on one of the qubits in the Bell State that he has, and obtains a result corresponding to one of the four Bell States. At this time, the state of the qubit that Bob has can change according to the result of Alice's Bell State Measurement, as shown in Table 5 below. Specifically, Table 5 exemplifies the change in Bob's qubit according to the result of Alice's Bell State Measurement.

[0177]

[0178] [4] Classical Transmission: Alice encodes the Bell State Measurement result into two classical bits and transmits it to Bob through the classical channel.

[0179] [5] Quantum Post-processing: Bob performs a unitary operation on the remaining qubit of the Bell State he has based on the two bits of information received from Alice to obtain the quantum information that Alice wanted to transmit. Obtain the same quantum state as .

[0180] Quantum Direct Communication (QDC)

[0181] Quantum direct communication (QDC) shares similarities with quantum key distribution (QKD), a 4 / 5G secure communication technology, in that both techniques securely transmit classical message information. However, QKD utilizes the quantum mechanical property of unclonability to share symmetric secret key information between the sender and receiver via a quantum channel, whereas QDC shares the classical message information directly via the quantum channel, rather than the secret key.

[0182] The QDC technology family includes quantum secure direct communication (QSDC), which boasts high security by preventing information leaks related to transmitted information. It also includes a two-step QSDC technique that utilizes entangled light sources. This is described in detail below with reference to Figure 12.

[0183] Figure 12 is a diagram illustrating superdense coding. Two-step QSDC is a technique derived from superdense coding, as shown in Figure 12. Specifically, Two-step QSDC is a technique for securely transmitting 2 bits of classical information using the four types of single entangled photons (EPR-pairs) of the mathematical formula 2 below.

[0184]

[0185] Superdense coding is a technique that enables classical information to be transmitted using quantum communication. Using superdense coding, a transmitter can transmit two bits of classical information to a distant receiver using a single qubit through a quantum channel. When using superdense coding, the transmitter is assumed to possess the first entangled qubit, and the receiver is assumed to possess the second entangled qubit. The qubit that the transmitter wishes to transmit can be one of four cases: '00', '01', '10', and '11'. For each of the four cases, the transmitter performs a qubit operation (expressed in the form of I, Z, X, iY) corresponding to each of the four cases on the entangled qubits it owns, and then transmits the information through the quantum channel. Each operation performed by the transmitter can be understood as transforming the entangled state shared by the transmitter and receiver into a different basis that is orthogonal to each other. The receiver measures the received qubit and its own qubit (the second qubit in the entangled state) to restore the two bits of information transmitted by the transmitter.

[0186] Referring to Figure 12, SR (Storage lines) 1 to 4 are optical delay lines that serve as quantum memories, CE (Checking Eavesdropping) 1 and 2 check for the presence of an eavesdropper, CM (Coding Message) encodes classical message information to be transmitted from the transmitter (Alice) to the receiver (Bob), EPR source generates an entangled light source, and Bell state measurement measures entangled photon pairs.

[0187] In two-step QSDC, unlike super dense coding, the entangled photon pair is not transmitted all at once, but is transmitted in two steps through an upper quantum channel and a lower quantum channel. In order to eavesdrop on the entangled light source, information on both sides of the entangled photon pair must be known to determine the transmitted information through measurement. Therefore, in the two-step technique, one side of the entangled photon pair is sent first to verify its safety from eavesdropping, and only when safety is guaranteed is the message information to be sent coded and transmitted on the remaining part of the photon pair.

[0188] The problems to be solved by this specification are as follows.

[0189] Secure communication through mediators

[0190] There are instances where communication through an intermediary is necessary, such as when communicating through a bank. In quantum communication, quantum memory is sometimes needed, such as when identifying eavesdroppers when utilizing quantum states. Quantum memory is not easy to implement, and currently available quantum memory suffers from excessive optical attenuation depending on the channel length. Therefore, a quantum communication protocol that utilizes an intermediary and enables communication without the use of quantum memory is needed.

[0191] Below, a method for constructing an entanglement-based CQC protocol without quantum memory is specifically examined with reference to FIGS. 13 and 14.

[0192] Proposed Quantum Dialogue (QD) protocol

[0193] Hereinafter, "publication" refers to transmission via a classical channel, not a quantum channel. For example, "Alice (Bob) discloses information" may mean Alice (Bob) transmits the information to Bob (Alice) and / or Charlie via a classical channel.

[0194] Fig. 13 is a diagram illustrating the structure of a quantum communication technique according to an embodiment of the present specification. Specifically, Fig. 13 illustrates the structure of the CQC protocol.

[0195] The structure in Figure 13 does not contain quantum memory. This is because Alice and Bob used a method to detect single photons and verify QBER.

[0196] The proposed CQC protocol works as follows.

[0197] ①: Generating entangled photon sequences for communication

[0198] Alice and Bob ask Charlie to create entanglement photons.

[0199] Charlie is Entanglement photon pairs, ) is prepared. Entangled photon pairs ( ), subscript Is and superscript (=1, 2, ... ) represents the index of the corresponding entangled photon pair.

[0200] The following mathematical expression 3 is An example of an entangled photon pair is shown.

[0201]

[0202] ② Step 2: Single photon detection

[0203] Alice and Bob use single-photon detectors to measure the photons they receive from Charlie.

[0204] Alice and Bob A sequence with elements , Each one creates

[0205] The values ​​that each element can have are 0 or 1. If 0 is selected, the measurement is performed using the Computational basis, and if 1 is selected, the measurement is performed using the Hadamard basis. That is, Alice (Bob) is the generated sequence ( ) using a basis based on Measuring the entangled photons of a dog.

[0206] Alice (Bob) is the result of the measurement ( ) to save

[0207] Charlie to Alice and Bob Randomly select and inform the location of the QBER check of the dog

[0208] A set representing the QBER check location By definition, Alice and Bob are Select the case and , basis information and Reveals to Charlie.

[0209] Charlie is and QBER test is performed using the relationship. Specifically, the initial value Charlie, who knows this, checks the QBER from Alice and Bob's public information to determine if there is an eavesdropper. If the QBER value is greater than a predetermined value, the protocol is deemed unsafe and is abandoned (i.e., the process is aborted). If the QBER value is less than a predetermined value, the protocol continues (the process continues). Charlie discloses to Alice and Bob the information regarding whether the protocol / process can continue.

[0210] ③ Step 3: Basis sifting

[0211] Alice and Bob communicate through a public channel In case of and Alice and Bob use the same basis to obtain the results. and If it does not match, it is removed.

[0212] ④ Step 4: Information transmission

[0213] Decide who will transmit the information, Alice or Bob.

[0214] Message when Alice (Bob) is the sender ( ) to be transmitted as follows:

[0215] Alice (Bob)'s measurement value is ( ) message ( ) is the added value ( ) is disclosed through public channels.

[0216] Charlie first prepared the Bell state when he allowed Alice and Bob to communicate. is disclosed. (index ) is disclosed.

[0217] Bob (Alice) and ( ), ( ), ( ) using ( ) can be estimated.

[0218] FIG. 14 is a drawing for explaining the operation according to the structure of a quantum communication technique according to an embodiment of the present specification.

[0219] At 1410, Charlie shares entangled photon pairs with Alice and Bob. The hatched portions here represent photon pairs for QBER testing.

[0220] At 1420, Alice and Bob measure each pair of entangled photons. 14A and 14B represent the basis used for the measurement. Specifically, 14A is the computational basis, and 14B is the Hadamard basis.

[0221] At 1430, Alice and Bob exchange their measurement results ( , ) are stored. Alice and Bob store the hatched measurement results ( person , ) is sent to Charlie.

[0222] At 1440, Alice and Bob measured the results ( person and ) stores measurement results based on the same basis.

[0223]

[0224] Table 6 illustrates information transmission when Alice is the sender. Bob uses his basis and and disclosed Based on between can be estimated. Estimated Based on cast It can be estimated as above n, m related to the decision of Initial state It means n, m of .

[0225] The effects according to the embodiments of this specification are as follows.

[0226] In the presence of a Controller (Charlie), Alice and Bob can perform secure information transmission using a quantum channel.

[0227] Since both Alice and Bob can be senders and receivers, they can communicate by selecting a sender as needed.

[0228] Since no quantum memory / optical cables are used, no additional optical attenuation occurs along the channel length.

[0229] In terms of implementation, the operations of the first device (Alice or Bob) / second device (Bob or Alice) / third device (Charlie) according to the above-described embodiments can be processed by the devices of FIGS. 1 to 5 described above (e.g., processors (202a, 202b) of FIG. 2).

[0230] In addition, the operations of the first device (Alice or Bob) / second device (Bob or Alice) / third device (Charlie) according to the above-described embodiment may be stored in a memory (e.g., 204a, 204b of FIG. 2) in the form of a command / program (e.g., instruction, executable code) for driving at least one processor (e.g., processor (202a, 202b) of FIG. 2).

[0231] The embodiments described below are specifically described with reference to FIGS. 15 to 17 in terms of the operation of the first device, the second device, and the third device (e.g., 200a and 200b in FIG. 2). The methods described below are distinguished merely for the convenience of explanation, and it goes without saying that some components of one method may be substituted for some components of another method or may be applied in combination with each other.

[0232] The definitions of the first through third devices are as follows. The first device may refer to Alice, Bob, or the sender. The second device may refer to Bob, Alice, or the receiver. The third device may refer to Charlie or the controller.

[0233] Figure 15 is a flowchart illustrating a method performed by a first device according to one embodiment of the present disclosure. Steps S1510 to S1560 may be based on at least one of the steps of the proposed CQC protocol. Each step of S1510 to S1560 will be described in detail below.

[0234] In S1510, the first device measures first entangled photons based on entanglement photon pairs.

[0235] As a concrete example, the number of entangled photon pairs is Let us explain by assuming an individual case. Among the above entangled photon pairs, the one transmitted / shared to the first device The photons of the dog are the first entangled photons, and the one of the entangled photon pairs is transmitted / shared to the second device. The photons of the dog may be second-entangled photons.

[0236] In one embodiment, the measurement of the first entangled photons can be performed based on single photon detection.

[0237] In S1520, the first device transmits first measurement information related to a quantum bit error rate (QBER) check to the third device. Based on the QBER check, it is determined whether to proceed with the process based on the entangled photon pairs.

[0238] Specifically, QBER can be determined based on the first measurement information and the second measurement information transmitted from the second device to the third device.

[0239] The first measurement information may include i) first measurement values ​​selected for the QBER test among the first measurement values ​​and ii) bases related to the selected first measurement values.

[0240] The second measurement information may include i) second measurement values ​​selected for the QBER check among second measurement values ​​for second entangled photons received by the second device, and ii) basis values ​​associated with the selected second measurement values.

[0241] This is explained in more detail with reference to Step 2 described above.

[0242] The above first measurement values ​​are It can be ( is the index of the entangled photon pair). The first selected measurements are person It could be. may be a set of entangled photon pairs for QBER testing. The basis associated with the selected first measurement values ​​is person It could be.

[0243] The above second measurement values ​​are It can be. The above selected second measurements are person The bases related to the above selected second measurement values ​​may be person It could be.

[0244] In step S1530, the first device receives information from the third device regarding whether the process is to be continued. At this time, the information regarding whether the process is to be continued may be received based on a classical channel (or public channel).

[0245] For example, based on the QBER being greater than a set value: the process may be aborted. That is, the information regarding whether the process continues may indicate the abort of the process.

[0246] In S1540, the first device receives information about second bases related to measurements of the second device from the second device based on the continuation of the process.

[0247] Specifically, based on the QBER being less than or equal to the set value, the process can continue. That is, the information regarding whether the process continues can indicate the continuation of the process. Based on this, the following actions can be performed.

[0248] Information about first bases related to the remaining first measurement values, excluding the selected first measurement values ​​among the first measurement values, can be transmitted from the first device to the second device. The information about the first bases can be transmitted via a classical channel (or a public channel).

[0249] Information about the second bases related to the remaining second measurement values ​​excluding the selected second measurement values ​​among the second measurement values ​​can be transmitted from the second device to the first device.

[0250] For example, information about the first bases / second bases can be transmitted via a classical channel (or public channel).

[0251] For example, the first bases above person can mean. The above second bases are person can mean.

[0252] In S1550, the first device determines first measurement values ​​for the first entangled photons based on the same basis as the second basis.

[0253] For example, referring to Steps 2 to 3 described above, the first measurement values ​​are The first measurement values ​​based on the same bases may be person The second device has the same base as the can mean.

[0254] To be more specific, the entire first measurement values ​​( ) among the first measurement values ​​based on the same bases are the measurement values ​​for the first entangled photons selected for the QBER test ( person ) for the remaining first entangled photons ( person ) among the second device and the base are the same (in other words, = Based on ) can mean. This can be expressed in summary as follows.

[0255] About = Based on

[0256] In S1560, the first device transmits a message to the second device.

[0257] In one embodiment, the message may be generated based on the determined first measurement values ​​and message information of the first device. In this case, the message may be transmitted via a classical channel (or public channel).

[0258] For example, the message may be generated based on the sum of the determined first measurement values ​​and the message information. The message may be It can be. The first measurement values ​​determined above (in other words, About = Based on ), and the above message information is It could be.

[0259] In one embodiment, second measurement values ​​may be determined based on the same bases as the first bases among the second measurement values.

[0260] i) Initial state associated with the above entangled photon pairs (e.g. ), ii) the second measurement values ​​determined above (e.g. About = Based on ), iii) bases related to the second measurements determined above (e.g. for = ), based on the above message (e.g. ) from the above message information ( ) can be estimated.

[0261] In one embodiment, the first device may be Alice or Bob in the quantum communication system. The second device may be Bob or Alice in the quantum communication system.

[0262] The method may further include a step of receiving information related to a QBER test. Specifically, the first device receives information related to the QBER test from a third device. The information related to the QBER test may indicate entangled photon pairs for the QBER test among the entangled photon pairs. For example, the information related to the QBER test may include information on a set of entangled photon pairs for the QBER test (e.g., ) may be.

[0263] In the above method, at least one of steps S1510 to S1560 may be omitted. For example, in the above method, at least one of the operations based on a classical channel / public channel (e.g., at least one of S1520, S1530, S1540, and S1560) may be omitted.

[0264] The operations based on the steps S1510 to S1560 and receiving information related to the QBER test described above can be implemented by the device of FIG. 2. For example, the first device (200a or 200b) can control one or more transceivers (206a or 206b) and / or one or more memories (204a or 204b) to perform the operations based on the steps S1510 to S1560 and receiving information related to the QBER test.

[0265] Figure 16 is a flowchart illustrating a method performed by a second device according to another embodiment of the present disclosure. Steps S1610 to S1660 may be based on at least one of the steps of the proposed CQC protocol. Each step of S1610 to S1660 will be described in detail below.

[0266] In step S1610, the second device measures second entangled photons based on entangled photon pairs. In one embodiment, the measurement of the second entangled photons may be performed based on single photon detection. S1610 corresponds to S1510 of FIG. 15, and thus, a redundant description thereof will be omitted.

[0267] In S1620, the second device transmits second measurement information related to a quantum bit error rate (QBER) check to the third device. Based on the QBER check, it is determined whether to proceed with the process based on the entangled photon pairs. The QBER can be determined based on the first measurement information and the second measurement information transmitted from the first device to the third device.

[0268] The first measurement information may include i) first measurement values ​​selected for the QBER check among the first measurement values ​​for the first entangled photons received by the first device, and ii) basis values ​​associated with the selected first measurement values.

[0269] The second measurement information may include i) second measurement values ​​selected for the QBER test among the second measurement values ​​and ii) bases related to the selected second measurement values.

[0270] S1620 corresponds to S1520 of Fig. 15, and duplicate description is omitted.

[0271] At S1630, the second device receives information from the third device as to whether the process is to be continued.

[0272] For example, based on the QBER being greater than a set value: the process may be aborted. That is, the information regarding whether the process continues may indicate the abort of the process.

[0273] S1630 corresponds to S1530 of Fig. 15, and duplicate description is omitted.

[0274] In S1640, the second device receives information about first bases related to measurements of the first device from the first device based on the continuation of the process.

[0275] Specifically, based on the QBER being less than or equal to the set value, the process can continue. That is, the information regarding whether the process continues can indicate the continuation of the process. Based on this, the following actions can be performed.

[0276] Information about first bases related to the remaining first measurement values ​​excluding the selected first measurement values ​​among the first measurement values ​​can be transmitted from the first device to the second device.

[0277] Information about second bases related to the remaining second measurement values, excluding the selected second measurement values ​​among the second measurement values, can be transmitted from the second device to the first device.

[0278] S1640 corresponds to S1540 of Fig. 15, and duplicate description is omitted.

[0279] At S1650, the second device determines second measurement values ​​based on the same basis as the first basis among the second measurement values ​​for the second entangled photons. S1650 corresponds to S1550 of FIG. 15, and thus, a duplicate description is omitted.

[0280] For example, referring to Steps 2 to 3 described above, the second measurement values ​​are The second measurement values ​​based on the same bases may be person The first device and the base are the same can mean.

[0281] To be more specific, the entire second measurement values ​​( ) among the second measurement values ​​based on the same bases are the measurement values ​​for the second entangled photons selected for the QBER test ( person ) for the remaining second entangled photons ( person ) among the first device and the base are the same (in other words, = Based on ) can mean. This can be expressed in summary as follows.

[0282] About = Based on

[0283] In S1660, the second device receives a message from the first device.

[0284] In one embodiment, message information of the first device can be estimated from the message based on the initial state associated with the entangled photon pairs and the determined second measurement values.

[0285] Specifically, the message information can be estimated from the message based on i) the initial state of the entangled photons, ii) the determined second measurement values, and iii) basis values ​​associated with the determined second measurement values.

[0286] In one embodiment, the message may be generated based on a sum of i) first measurement values ​​based on the same bases as the second bases among the first measurement values ​​and ii) the message information.

[0287] The method may further include a step of receiving information related to a QBER test. Specifically, the second device receives information related to the QBER test from the third device. The information related to the QBER test may indicate entangled photon pairs for the QBER test among the entangled photon pairs. For example, the information related to the QBER test may include information on a set of entangled photon pairs for the QBER test (e.g., ) may be.

[0288] In the above method, at least one of steps S1610 to S1660 may be omitted. For example, in the above method, at least one of the operations based on a classical channel / public channel (e.g., at least one of S1620, S1630, S1640, and S1660) may be omitted.

[0289] The operations based on the steps S1610 to S1660 and receiving information related to the QBER test described above can be implemented by the device of FIG. 2. For example, the second device (200a or 200b) can control one or more transceivers (206a or 206b) and / or one or more memories (204a or 204b) to perform the operations based on the steps S1610 to S1660 and receiving information related to the QBER test.

[0290] Figure 17 is a flowchart illustrating a method performed by a third device according to another embodiment of the present disclosure. Steps S1710 to S1770 may be based on at least one of the steps of the proposed CQC protocol. Each step of S1710 to S1770 will be described in detail below.

[0291] In S1710, the third device transmits first entangled photons and second entangled photons based on entanglement photon pairs to the first device and the second device, respectively.

[0292] As a concrete example, the number of entangled photon pairs is Let us explain by assuming an individual case. Among the above entangled photon pairs, the one transmitted / shared to the first device The photons of the dog are the first entangled photons, and the one of the entangled photon pairs is transmitted / shared to the second device. The photons of the dog may be second-entangled photons.

[0293] S1710 corresponds to S1510 of Fig. 15, and duplicate description is omitted.

[0294] In S1720, the third device transmits information related to a quantum bit error rate (QBER) check to the first device and the second device. The information related to the QBER check may indicate entangled photon pairs for the QBER check among the entangled photon pairs.

[0295] At S1730, the third device receives first measurement information related to the QBER test from the first device. The first measurement information may include i) first measurement values ​​selected for the QBER test among the first measurement values ​​for the first entangled photons, and ii) basis values ​​related to the selected first measurement values. S1730 corresponds to S1520 of FIG. 15, and thus, a duplicate description is omitted.

[0296] At S1740, the third device receives second measurement information related to the QBER test from the second device. The second measurement information may include i) second measurement values ​​selected for the QBER test among the second measurement values ​​for the second entangled photons, and ii) basis values ​​related to the selected second measurement values. S1740 corresponds to S1620 of FIG. 16, and thus, a duplicate description is omitted.

[0297] In S1750, the third device performs the QBER check based on the first measurement information and the second measurement information. Based on the QBER check, it is determined whether to proceed with the process based on the entangled photon pairs.

[0298] Specifically, QBER can be determined based on the first measurement information and the second measurement information.

[0299] Based on the above QBER being greater than the set value: the process may be aborted. That is, information on whether the process continues may indicate the abort of the process.

[0300] Based on the QBER being less than or equal to the set value, information on whether the process is to be continued may indicate the continuation of the process. Information on the initial state of the entangled photon pairs may be transmitted to the first device and the second device.

[0301] At S1760, the third device transmits information on whether the process is to be continued to the first device and the second device. S1760 corresponds to S1530 of FIG. 15 and S1630 of FIG. 16, and thus, redundant descriptions are omitted.

[0302] In S1770, the third device transmits information about the initial state associated with the entangled photon pairs to the first device and the second device. For example, the information about the initial state may be transmitted based on a classical channel (or public channel).

[0303] In the above method, at least one of steps S1710 to S1770 may be omitted. For example, in the above method, at least one of the operations based on a classical channel / public channel (e.g., at least one of S1720, S1730, S1740, and S1760) may be omitted.

[0304] The operations based on S1710 to S1770 described above can be implemented by the device of FIG. 2. For example, the third device (200a or 200b) can control one or more transceivers (206a or 206b) and / or one or more memories (204a or 204b) to perform the operations based on S1710 to S1770.

[0305] Here, the wireless communication technology implemented in the wireless device (200a, 200b) of the present specification may include not only LTE, NR, and 6G, but also Narrowband Internet of Things for low-power communication. At this time, for example, NB-IoT technology may be an example of LPWAN (Low Power Wide Area Network) technology, and may be implemented with standards such as LTE Cat NB1 and / or LTE Cat NB2, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (200a, 200b) of the present specification may perform communication based on LTE-M technology. At this time, for example, LTE-M technology may be an example of LPWAN technology, and may be called by various names such as eMTC (enhanced Machine Type Communication). For example, LTE-M technology can be implemented by at least one of various standards such as 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL (non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication, and / or 7) LTE M, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (200a, 200b) of the present specification can include at least one of ZigBee, Bluetooth, and Low Power Wide Area Network (LPWAN) considering low-power communication, and is not limited to the above-described names. For example, ZigBee technology can create personal area networks (PAN) related to small / low-power digital communication based on various standards such as IEEE 802.15.4, and can be called by various names.

[0306] The embodiments described above are combinations of the components and features of the present disclosure in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, it is also possible to combine some components and / or features to form an embodiment of the present disclosure. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form an embodiment or may be incorporated as a new claim through a post-application amendment.

[0307] Embodiments according to the present specification may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0308] When implemented via firmware or software, an embodiment of the present specification may be implemented in the form of a module, procedure, function, or the like that performs the functions or operations described above. The software code may be stored in memory and executed by a processor. The memory may be located within or external to the processor and may exchange data with the processor via various known means.

[0309] It will be apparent to those skilled in the art that this specification may be embodied in other specific forms without departing from the essential characteristics thereof. Therefore, the foregoing detailed description should not be construed in any way as limiting but rather as illustrative. The scope of this specification should be determined by a reasonable interpretation of the appended claims, and all changes within the scope of equivalents herein are intended to be included within the scope of this specification.

Claims

1. A method performed by a first device in a wireless communication system, A step of measuring first entangled photons based on entanglement photon pairs; A step of transmitting first measurement information related to a quantum bit error rate (QBER) check to a third device, wherein based on the QBER check, it is determined whether to proceed with a process based on the entangled photon pairs; A step of receiving information on whether the process is to be continued from the third device; Based on the continuation of the above process, a step of receiving information about second bases related to the measurement of the second device from the second device; A step of determining first measurement values ​​based on the same basis as the second basis among the first measurement values ​​for the first entangled photons; and comprising the step of transmitting a message to the second device; A method characterized in that the message is generated based on the determined first measurement values ​​and message information of the first device.

2. In paragraph 1, A method characterized in that the measurement of the first entangled photons is performed based on single photon detection.

3. In paragraph 1, The first device is Alice or Bob in the quantum communication system, A method characterized in that the second device is Bob or Alice in the quantum communication system.

4. In paragraph 1, Further comprising a step of receiving information related to the QBER test from the third device, A method characterized in that the information related to the QBER test indicates entangled photon pairs for the QBER test among the entangled photon pairs.

5. In paragraph 4, QBER is determined based on the first measurement information and the second measurement information transmitted from the second device to the third device, The first measurement information includes i) first measurement values ​​selected for the QBER test among the first measurement values ​​and ii) bases related to the selected first measurement values, A method characterized in that the second measurement information comprises i) second measurement values ​​selected for the QBER check among second measurement values ​​for second entangled photons received by the second device, and ii) basis values ​​associated with the selected second measurement values.

6. In paragraph 5, Based on the above QBER being greater than the set value: A method characterized in that the above process is interrupted.

7. In paragraph 5, Based on the above QBER being less than or equal to the set value: Information about the first bases related to the remaining first measurement values ​​excluding the selected first measurement values ​​among the first measurement values ​​is transmitted from the first device to the second device, A method characterized in that information about the second bases related to the remaining second measurement values ​​excluding the selected second measurement values ​​among the second measurement values ​​is transmitted from the second device to the first device.

8. In paragraph 1, A method characterized in that the above message is generated based on the sum of the determined first measurement values ​​and the message information.

9. In paragraph 7, Among the second measurement values, second measurement values ​​based on the same bases as the first bases are determined, A method characterized in that the message information is estimated from the message based on i) an initial state associated with the entangled photon pairs, ii) the determined second measurement values, and iii) basis associated with the determined second measurement values.

10. In the first device, One or more transmitters and receivers; one or more processors; and One or more memories connected to said one or more processors and storing instructions, A first device characterized in that the instructions, based on being executed by the one or more processors, set the one or more processors to perform all steps of the method according to any one of claims 1 to 9.

11. In one or more non-transitory computer-readable media storing instructions, One or more non-transitory computer-readable media characterized in that the instructions executable by one or more processors cause the one or more processors to perform all steps of the method according to any one of claims 1 to 9.

12. In a method performed by a third device in a wireless communication system, A step of transmitting first entangled photons and second entangled photons based on entanglement photon pairs to a first device and a second device, respectively; A step of transmitting information related to a quantum bit error rate (QBER) test to the first device and the second device, The information related to the above QBER test indicates entangled photon pairs for the QBER test among the entangled photon pairs; A step of receiving first measurement information related to the QBER test from the first device; A step of receiving second measurement information related to the QBER test from the second device; A step of performing the QBER check based on the first measurement information and the second measurement information, wherein whether to proceed with the process based on the entangled photon pairs is determined based on the QBER check; A step of transmitting information on whether the above process is to be continued to the first device and the second device; and A method comprising the step of transmitting information about an initial state associated with the entangled photon pairs to the first device and the second device.

13. In paragraph 12, QBER is determined based on the first measurement information and the second measurement information, Based on the above QBER being greater than the set value: the process is aborted, Based on the above QBER being less than or equal to the above set value: A method characterized in that information about the initial state of the entangled photon pairs is transmitted to the first device and the second device.

14. In paragraph 12, The first measurement information includes i) first measurement values ​​selected for the QBER check among the first measurement values ​​for the first entangled photons, and ii) basis values ​​associated with the selected first measurement values, A method characterized in that the second measurement information comprises i) second measurement values ​​selected for the QBER check among the second measurement values ​​for the second entangled photons, and ii) basis values ​​associated with the selected second measurement values.

15. In the third device, One or more transmitters and receivers; one or more processors; and One or more memories connected to said one or more processors and storing instructions, A third device characterized in that the instructions, based on being executed by the one or more processors, set the one or more processors to perform all steps of the method according to any one of claims 12 to 14.

16. In one or more non-transitory computer-readable media storing instructions, One or more non-transitory computer-readable media characterized in that the instructions executable by one or more processors cause the one or more processors to perform all steps of the method according to any one of claims 12 to 14.

17. In a method performed by a second device in a wireless communication system, A step of measuring second entangled photons based on entanglement photon pairs; A step of transmitting second measurement information related to a quantum bit error rate (QBER) check to a third device, wherein based on the QBER check, it is determined whether to proceed with a process based on the entangled photon pairs; A step of receiving information on whether the process is to be continued from the third device; Based on the continuation of the above process, a step of receiving information about first bases related to the measurement of the first device from the first device; A step of determining second measurement values ​​based on the same basis as the first basis among the second measurement values ​​for the second entangled photons; and A step of receiving a message from the first device; comprising: A method characterized in that message information of the first device is estimated from the message based on the initial state associated with the entangled photon pairs and the determined second measurement values.

18. In paragraph 17, A method characterized in that the measurement of the second entangled photons is performed based on single photon detection.

19. In paragraph 17, QBER is determined based on the first measurement information and the second measurement information transmitted from the first device to the third device, The first measurement information includes i) first measurement values ​​selected for the QBER check among the first measurement values ​​for the first entangled photons received by the first device, and ii) basis values ​​associated with the selected first measurement values, A method characterized in that the second measurement information includes i) second measurement values ​​selected for the QBER test among the second measurement values ​​and ii) bases related to the selected second measurement values.

20. In paragraph 19, Based on the above QBER being greater than the set value: A method characterized in that the process based on the above entangled photon pairs is interrupted.

21. In paragraph 20, Based on the above QBER being less than or equal to the set value: Information about the first bases related to the remaining first measurement values ​​excluding the selected first measurement values ​​among the first measurement values ​​is transmitted from the first device to the second device, A method characterized in that information about second bases related to the remaining second measurement values ​​excluding the selected second measurement values ​​among the second measurement values ​​is transmitted from the second device to the first device.

22. In paragraph 21, A method characterized in that the message information is estimated from the message based on i) the initial state of the entangled photons, ii) the determined second measurement values, and iii) bases related to the determined second measurement values.

23. In paragraph 21, A method characterized in that the message is generated based on the sum of i) first measurement values ​​based on the same bases as the second bases among the first measurement values ​​and ii) the message information.

24. In the second device, One or more transmitters and receivers; one or more processors; and One or more memories connected to said one or more processors and storing instructions, A second device characterized in that the instructions, based on being executed by the one or more processors, set the one or more processors to perform all steps of the method according to any one of claims 17 to 23.

25. In one or more non-transitory computer-readable media storing instructions, One or more non-transitory computer-readable media characterized in that the instructions executable by one or more processors cause the one or more processors to perform all steps of the method according to any one of claims 17 to 23.

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