Method for transmitting quantum states, method for verifying quantum states, and system therefor

Abstract

A method for transmitting quantum states, a method for verifying quantum states, and a system for doing so are provided. [Solution] A method for transmitting quantum states performed by a computing device includes the steps of generating a first quantum state, generating a second quantum state using a dummy state, encoding the generated second quantum state, injecting an uncorrectable error into the encoded second quantum state to generate a third quantum state, and transmitting the generated third quantum state to a receiving node.

Description

[Technical Field]

[0001] This disclosure relates to a method for transmitting quantum states. More specifically, it provides a method for transmitting quantum states and a method for verifying forgery and tampering with quantum states, which enable easy verification of forgery and tampering in quantum communications. [Background technology]

[0002] A quantum network refers to communication that connects remote quantum devices, such as quantum computers, using both quantum and classical links. Security is a crucial requirement for successful long-distance communication. To meet these security requirements, it is essential to efficiently and securely transmit arbitrary quantum states over long distances.

[0003] On the other hand, quantum teleportation is a quantum protocol that transmits arbitrary quantum states by utilizing quantum entanglement states and quantum and classical links. Quantum teleportation requires a pre-shared entanglement pair between the transmitting and receiving nodes. For longer distances, entanglement swapping is necessary to extend the range.

[0004] Entanglement swapping has a 50% success rate in physical Bell state measurement (BSM) in linear optical systems; therefore, as the distance increases and the number of nodes increases, the success rate decreases exponentially.

[0005] To mitigate this, logic Bell state measurements using quantum error correction codes (QECC) are performed, resulting in a code length of n. bsm Based on this, the probability of success is

[0006]

number

[0007] It can be improved up to. However, such a method increases the overhead. In particular, when considering purification, the overhead may further increase. Also, when the distance between the transmitting node and the receiving node is very long and multiple stages of entanglement swapping and purification are required, the overhead can increase exponentially in proportion to the number of relay nodes.

[0008] From such a background, there is an increasing demand for technologies that improve the security of quantum channels while suppressing the increase in overhead.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

[0010] [Problems to be Solved by the Invention] Some embodiments of the present disclosure aim to solve the technical problem of providing a method for transmitting a quantum state while suppressing the generation of overhead and a system therefor.

[0011] <A Some other technical problems that some embodiments of the present disclosure aim to solve are to provide a method and a system therefor that can accurately verify the forgery and tampering of quantum states.

[0012] Some other technical problems that some embodiments of the present disclosure aim to solve are to provide a method and a system therefor that can stably transmit data over an extremely long distance through a plurality of relay nodes.

[0013] The technical challenges of this disclosure are not limited to those described above, and other technical challenges not mentioned will be clearly understood by a person of the ordinary skill in the art of this disclosure from the following description.

[0014] [Means for solving the problem] A method for transmitting quantum states performed by a computing device according to one embodiment of the present disclosure for solving the aforementioned technical problems may include the steps of: generating a second quantum state using a first quantum state and a dummy state; encoding the generated second quantum state; generating a third quantum state by injecting an uncorrectable error into the encoded second quantum state; and transmitting the generated third quantum state to a receiving node.

[0015] Furthermore, the step of generating the second quantum state may include the step of acquiring a dummy state related to the mutually unbiased basis, and the step of randomly mixing the acquired dummy state with the first quantum state to generate the second quantum state.

[0016] Furthermore, the step of generating the third quantum state may include the steps of encoding the second quantum state based on one or more parameters related to a quantum error correction code, acquiring the uncorrectable error, and injecting the acquired uncorrectable error into the second quantum state encoded based on the one or more parameters.

[0017] Furthermore, the aforementioned uncorrectable error may include the Pauli error operator.

[0018] Furthermore, the method for transmitting quantum states may further include the steps of acquiring the syndrome of the uncorrectable error and transmitting the acquired syndrome to the receiving node.

[0019] Furthermore, the computing device may transmit the syndrome to the receiving node via a classical channel and the third quantum state to the receiving node via a quantum channel.

[0020] Furthermore, the quantum state transmission method may further include, after the step of transmitting the third quantum state to the receiving node, the step of transmitting the uncorrectable error to the receiving node when a first acknowledgment message relating to the successful reception of the third quantum state is received from the receiving node.

[0021] Furthermore, the computing device may transmit the uncorrectable error to the receiving node via a classical channel.

[0022] Furthermore, the quantum state transmission method may further include, after the step of transmitting the uncorrectable error to the receiving node, the step of transmitting a second acknowledgment message relating to the successful verification of the third quantum state to the receiving node, to the receiving node a permutation operator and an encoding operator for encoding the zero auxiliary states into an unbiased state.

[0023] Furthermore, the permutation operator and the encoding operator can be transmitted to the receiving node via a classical channel.

[0024] A method performed by a computing device according to one embodiment of the present disclosure for solving the aforementioned technical problems may include the steps of: receiving a quantum state from a transmitting node; receiving an uncorrectable error from the transmitting node; applying the uncorrectable error to the quantum state to obtain a first syndrome; and determining whether the obtained first syndrome matches a predetermined second syndrome to perform a first verification of the quantum state.

[0025] Furthermore, the predetermined second syndrome may be an all-zero syndrome in which the bits are all zero.

[0026] Furthermore, the quantum state verification method may further include, before the step of receiving the uncorrectable error, the step of receiving a syndrome from the transmitting node, and the step of verifying the quantum channel based on whether the syndrome extracted from the quantum state matches the received syndrome.

[0027] Furthermore, the step of receiving the uncorrectable error may include, if the verification of the quantum channel is successful, transmitting a first acknowledgment message to the transmitting node indicating that the quantum state has been successfully received, and receiving the uncorrectable error from the transmitting node as a response to the transmission of the first acknowledgment message.

[0028] Furthermore, the quantum state verification method may further include, if the first verification is successful, receiving from the transmitting node a permutation operator and an encoding operator for encoding the zero auxiliary states into a state that is not biased toward each other, and performing a second verification of the dummy states included in the quantum state based on the permutation operator and the encoding operator.

[0029] Furthermore, the quantum state, after being transmitted from the transmitting node, can be transmitted to the computing device via one or more relay nodes.

[0030] A computing device according to one embodiment of the present disclosure for solving the aforementioned technical problems includes one or more processors and a memory for storing a computer program executed by the one or more processors, the computer program may include instructions for an operation to generate a second quantum state using a first quantum state and a dummy state, an operation to encode the generated second quantum state, an operation to generate a third quantum state by injecting an uncorrectable error into the encoded second quantum state, and an operation to transmit the generated third quantum state to a receiving node.

[0031] A computing device according to one embodiment of the present disclosure for solving the aforementioned technical problems includes one or more processors and a memory for storing a computer program executed by the one or more processors, the computer program may include instructions for an operation to receive a quantum state from a transmission node, an operation to receive an uncorrectable error from the transmission node, an operation to apply the uncorrectable error to the quantum state to obtain a first syndrome, and an operation to determine whether the obtained first syndrome matches a predetermined second syndrome and to perform a first verification of the quantum state.

[0032] A computer program coupled to a computing device according to one embodiment of the present disclosure for solving the aforementioned technical problems can be stored on a computer-readable recording medium to perform the steps of generating a second quantum state using a first quantum state and a dummy state, encoding the generated second quantum state, generating a third quantum state by injecting an uncorrectable error into the encoded second quantum state, and transmitting the generated third quantum state to a receiving node.

[0033] A computer program coupled to a computing device according to one embodiment of the present disclosure for solving the aforementioned technical problems can be stored on a computer-readable recording medium to perform the steps of: receiving a quantum state from a transmission node; receiving an uncorrectable error from the transmission node; applying the uncorrectable error to the quantum state to obtain a first syndrome; and determining whether the obtained first syndrome matches a predetermined second syndrome to perform a first verification of the quantum state. [Brief explanation of the drawing]

[0034] [Figure 1] This figure illustrates a quantum communication system according to one embodiment of the present disclosure. [Figure 2]According to one embodiment of the present disclosure, this is a signal processing diagram illustrating a method in which a quantum state is transmitted and verified in a quantum communication system. [Figure 3] This is a flowchart illustrating a method by which a transmitting node generates and transmits state information to a receiving node according to one embodiment of the present disclosure. [Figure 4] This is a flowchart illustrating how a transmitting node transmits verification data to a receiving node according to one embodiment of the present disclosure. [Figure 5] This is a flowchart illustrating a method for verifying a quantum state at a receiving node according to one embodiment of the present disclosure. [Figure 6] This figure illustrates a quantum communication system for long-distance transmission according to one embodiment of the present disclosure. [Figure 7] This is an exemplary hardware configuration diagram showing how computing systems can be implemented in various embodiments. [Modes for carrying out the invention]

[0035] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The advantages and features of the present disclosure, and how to achieve them, will become clearer with reference to the embodiments described below in detail, along with the accompanying drawings. However, the technical ideas of the present disclosure are not limited to the embodiments described below and can be realized in a variety of different forms, and the embodiments described below are provided merely to complete the technical ideas of the present disclosure and to fully inform those who are ordinary skill in the art to which the present disclosure belongs, and the technical ideas of the present disclosure are defined only by the scope of the claims.

[0036] Please note that when assigning reference numerals to components in each drawing, the same reference numeral is used for the same component, even if it is shown in different drawings. Furthermore, in this disclosure, if a detailed explanation of a relevant known configuration or function is deemed to obscure the gist of this disclosure, such detailed explanation will be omitted.

[0037] Unless otherwise defined, all terms used herein (including technical and scientific terms) should be used in a sense that is commonly understood by a person of ordinary skill in the art to which this disclosure pertains. Furthermore, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly defined otherwise. Terms used herein are for illustrative purposes only and are not intended to limit this disclosure. In this specification, singular forms include plural forms unless otherwise specified.

[0038] In addition, terms such as 1, 2, A, B, (a), and (b) may be used to describe the components of this disclosure. These terms are used solely to distinguish a component from other components and do not limit the nature, order, or sequence of the component in question. Where it is stated that a component is “connected,” “joined,” or “linked” to another component, it should be understood that this may include cases where the component is directly connected or linked to the other component, as well as cases where another component is interposed between the two components to “connect,” “join,” or “linked.”

[0039] In this specification, “comprises” and / or “comprising” means that the components, stages, operations and / or elements described do not exclude the presence or addition of one or more other components, stages, operations and / or elements.

[0040] Several embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.

[0041] Figure 1 illustrates a quantum communication system according to one embodiment of the present disclosure.

[0042] As illustrated in Figure 1, a quantum communication system may include a transmitting node 110 and a receiving node 120. Here, each of the transmitting node 110 and the receiving node 120 may be a computing device including one or more processors and memory. For example, each of the transmitting node 110 and the receiving node 120 may be a computing device including components as shown in Figure 7.

[0043] Multiple communication channels may be formed between the transmitting node 110 and the receiving node 120. According to one embodiment, a classical channel 130 and a quantum channel 140 may be formed between the transmitting node 110 and the receiving node 120. The classical channel 130 is a verified communication channel, and data transmitted and received through the classical channel 130 can be considered reliable. The quantum channel 140 is a channel with high loss and noise, and data transmitted and received through the quantum channel 140 can be considered less reliable compared to the classical channel 130.

[0044] Transmitting node 110 received an uncorrectable error (hereinafter referred to as "E") un The transmitted node 110 can transmit a quantum state into which an uncorrectable error (referred to as "...") has been injected to the receiving node 120. According to one embodiment, the transmitting node 110 can generate a second quantum state using a first quantum state and a dummy state, encode the generated second quantum state, and then generate a third quantum state by injecting an uncorrectable error into the encoded second quantum state. Subsequently, the transmitting node 110 can transmit the generated third quantum state to the receiving node 120. Furthermore, the transmitting node 110 can transmit data necessary for verifying the quantum state to the receiving node 120.

[0045] The receiving node 120 may perform verification of the quantum state received from the transmitting node 110. Here, verification of the quantum state may include at least one of verifying whether the quantum state has been forged and tampered with by an external attack and verifying whether the quantum channel is good. According to one embodiment, the receiving node 120 receives the quantum state and uncorrectable errors (E) from the transmitting node 110. un) received an uncorrectable error (E un The system can apply this to the quantum state to obtain a syndrome. The receiving node 120 can also determine whether the obtained syndrome matches a predetermined syndrome and perform verification of the quantum state.

[0046] The following section describes a specific method for transmitting a quantum state from the transmitting node 110 to the receiving node 120, and for verifying the quantum state at the receiving node 120, with reference to Figure 2.

[0047] Figure 2 is a signal processing diagram illustrating a method by which a quantum state is transmitted and verified in a quantum communication system according to one embodiment of the present disclosure.

[0048] Referring to Figure 2, the transmitting node 110 can measure the bit error rate of the quantum channel and then determine various parameters to be applied to the quantum error correction code (QECC) based on the measured bit errors (S201). For example, the transmitting node 110 can determine the maximum number of errors that can be corrected by the QECC "t", the total number of qubits used for error correction "n", the number of logical qubits that actually hold the information "k", and the number of code distances "d" that can detect and correct the error code.

[0049] Next, the transmitting node 110 can generate multiple encryption keys (S203). For example, the transmitting node 110 can generate multiple encryption keys having a predetermined number of bits. For example, the transmitting node 110 can generate a first encryption key, a second encryption key, a third encryption key, and a fourth encryption key. Some of the four encryption keys may have the same number of bits, while all four encryption keys may have different numbers of bits. According to one embodiment, each of the first encryption key, the second encryption key, and the third encryption key may have the same number of bits (e.g., k-k' bits) and the same length as the dummy key described later, and the fourth encryption key may be larger than the first to third encryption keys. Such encryption keys are used when generating at least one of the first quantum state, the second quantum state, and the third quantum state described later.

[0050] Subsequently, the transmitting node 110 can generate a first quantum state (S205). According to one embodiment, the transmitting node 110 can generate arbitrary k'-qubit information as the first quantum state.

[0051]

number

[0052] any

[0053]

number

[0054] This can be expressed as shown in equation 1 below.

[0055]

number

[0056] Here, m i These are computational basis states, and c iThese are complex amplitudes associated with the basis states.

[0057] Next, the transmitting node 110 obtains dummy states related to mutually unbiased bases (MUB) in order to prevent external attacks, and the obtained dummy states

[0058]

number

[0059] A second quantum state can be generated by randomly interspersing (S207). In one embodiment, dummy states can be generated in advance and stored in the transmitting node 110. In some embodiments, when the quantum state to be transmitted is generated, the transmitting node 110 can randomly generate dummy states of a predetermined length.

[0060] According to one embodiment, the transmitting node 110 can generate a second quantum state by randomly mixing a first group of bits constituting a dummy state with a second group of bits constituting a quantum state, and randomly mixing the dummy state with the first quantum state. For example, the transmitting node 110 has two sets of states based on randomly positioned mutually unbiased basis bits (MUBs).

[0061]

number

[0062] In relation to the k-k' length

[0063]

number

[0064] of

[0065]

number

[0066] can be randomly mixed therein.

[0067]

Number

[0068] can be expressed by Equation 2.

[0069]

Number

[0070] Here, X and Z are Pauli operators, H is a Hadamard operator,

[0071]

Number

[0072] each of which can be an operator that is applied when the bit is 1 and is applied as an identity operator when the bit is 0. Also, U MUB can be an encoding operator for encoding 0 auxiliary states into a state with no bias from each other.

[0073] Thereafter, the transmission node 110 can generate a third quantum state (S209) by encoding the second quantum state using a quantum error correction code (QECC) and then injecting an uncorrectable error (E un ) into the encoded second quantum state. Here, the uncorrectable error (E un ) can be a bit or a bit string that cannot be corrected even using a quantum error correction code. Also, injecting an uncorrectable error (E un ) into the second quantum state means that a plurality of bits constituting the second quantum state and the uncorrectable error (E unThis means that one or more bits constituting the ) are operated on via a specific operator. In such cases, a third quantum state may be generated as a result of the operation.

[0074] The transmitting node 110 can encode the second quantum state using various parameters applied to the quantum error correction code (QECC). For example, the transmitting node 110 can encode the second quantum state based on the total number of qubits "n" used for error correction, the number of logical qubits "k" that actually hold the information, and the number of code distances "d" that can detect and correct the error code.

[0075] For QECC encoding based on [[n,k,d]]

[0076]

number

[0077] This can be expressed as shown in equation 3.

[0078]

number

[0079] Here,

[0080]

number

[0081] teeth

[0082]

number

[0083] This is an operator for permuting qubits.

[0084] The transmitting node 110 uses the QECC encoding operator (U E ) using

[0085]

number

[0086] It can be encoded as a logical state.

[0087]

number

[0088] This can be expressed as shown in equation 4 below. The encoded expression shown in equation 4 below

[0089]

number

[0090] This could be an encoded second quantum state.

[0091]

number

[0092] Subsequently, the transmitting node 110 has an error that cannot be corrected even via QECC (E un ) encoded

[0093]

number

[0094] It can be injected into. For example, an uncorrectable error (E un ) may include a randomly selected Pauli error operator. In such cases, an operation is performed based on the Pauli error operator and the encoded second quantum state, and a third quantum state may be generated as a result of the operation. Uncorrectable error (E un) can enhance security against external hacking attacks such as man-in-the-middle attacks and random attacks.

[0095] Uncorrectable error (E un ) is encoded

[0096]

number

[0097] When injected into and a third quantum state is generated, the third quantum state can be understood as being encrypted based on an uncorrectable error.

[0098] Encoded and encrypted (i.e., E un (It was injected.)

[0099]

number

[0100] This can be expressed as shown in equation 5.

[0101]

number

[0102] Subsequently, the transmitting node receives an injected uncorrectable error (E un ) calculate the syndrome(s),

[0103]

number

[0104] The calculated syndrome(s) can be transmitted to the receiving node (S211). According to one embodiment, the transmitting node 110

[0105]

number

[0106] The quantum channel 140 can transmit the θ, and the syndrome(s) can be transmitted via the classical channel 130.

[0107] Subsequently, the receiving node 120

[0108]

number

[0109] Upon receiving,

[0110]

number

[0111] The system can extract a syndrome from the data and determine whether the extracted syndrome matches the syndrome(s) received from the transmitting node 110. The receiving node 120 then...

[0112]

number

[0113] If the syndrome extracted from the data matches the received syndrome(s), the channel can be determined to be normal. Here, the channel determined to be normal may be quantum channel 140.

[0114] If the receiving node 120 determines that the channel is normal,

[0115]

number

[0116] A first acknowledgment message (Ack1) may be transmitted to the transmitting node 110 to inform it that the message has been successfully received (S213).

[0117] Meanwhile, receiving node 120

[0118]

number

[0119] If the syndrome extracted does not match the received syndrome(s), the channel may be determined to be abnormal. Here, the channel determined to be abnormal may be quantum channel 140, which is in an unstable state due to the generation of a lot of noise.

[0120] If the receiving node 120 determines that the channel is abnormal, it will, based on the syndrome(s) received via the classical channel,

[0121]

number

[0122] Error correction can be performed for this. If the receiving node 120 successfully corrects the error or determines that the channel is normal, it may transmit a first acknowledgment message (Ack1) to the transmitting node 110.

[0123] Subsequently, when the transmitting node 110 receives the first acknowledgment message (Ack1), it receives an uncorrectable error (E un ) can be transmitted to the receiving node 120 (S215). According to one embodiment, the transmitting node 110 transmits an uncorrectable error (E) via the classical channel. un ) can be transmitted.

[0124] Next, the receiving node 120

[0125]

number

[0126] Uncorrectable error (E unAfter applying the error, an uncorrectable error (E un ) is applied to extract the first syndrome,

[0127]

number

[0128] A first verification can be performed against (S217). According to one embodiment, the receiving node 120 receives an uncorrectable error (E un ) was applied

[0129]

number

[0130] Determine whether the first syndrome extracted from the data has a predetermined value.

[0131]

number

[0132] A first verification can be performed on this. For example, the receiving node 120 can perform the first verification by determining whether the extracted first syndrome matches a second syndrome composed of predetermined values.

[0133]

number

[0134] and uncorrectable errors (E un If none of the above have been forged or altered, then the first syndrome may be consistent with the second syndrome, which consists of predetermined values.

[0135] For example, the receiving node 120 may determine that the first verification was successful if the first syndrome matches the second syndrome, which consists entirely of zeros, and if the first syndrome does not match the second syndrome, it may determine that the first verification of the third quantum state has failed and interrupt the subsequent process. That is, if the first syndrome is not entirely zero, the receiving node 120 may determine that the third quantum state and / or an uncorrectable error (E) have been affected by an external attack. un If it is determined that at least one of the documents has been forged or altered, the subsequent process may be terminated.

[0136] The receiving node 120 is in the third quantum state and / or an uncorrectable error (E un If it is determined that at least one of the ) has been forged or tampered with, a warning message informing the transmitting node 110 of an external attack may be transmitted. In this case, the receiving node 120 may transmit the warning message to the transmitting node 110 using all or some of the quantum channel 140 and classical channel 130.

[0137] On the other hand, if the receiving node 120 determines that the first verification was successful, it may transmit a second acknowledgment message (Ack2) related to the success of the first verification to the transmitting node 110 (S219).

[0138] When the transmitting node 110 receives the second acknowledgment message (Ack2),

[0139]

number

[0140] and encoding operator (U MUB ) can be transmitted to the receiving node 120 (S221). Here,

[0141]

number

[0142] This was used when encoding the second quantum state.

[0143]

number

[0144] It can be an operator that permutates the qubits. Also, the encoding operator (U MUB ) can be an operator used when injecting a dummy state into the first quantum state, that is, an operator that encodes zero auxiliary states into a state that is unbiased towards each other. According to one embodiment, the transmitting node 110,

[0145]

number

[0146] and encoding operator (U MUB ) can be transmitted to the receiving node 120 via the classical channel 130.

[0147] Receiving node 120 received

[0148]

number

[0149] and encoding operator (U MUB ) using

[0150]

number

[0151] Included

[0152]

number

[0153] By determining whether it has been forged and altered,

[0154]

number

[0155] A second verification can be performed on (S223). For example, the receiving node 120 can perform the encoding operator (U MUB ) using

[0156]

number

[0157] Encoding can be performed on the and encoded data can be generated.

[0158]

number

[0159] Measurement result data can be generated from the dummy state included. Here, the measurement result data reflects the characteristics of the dummy state, and the receiving node 120,

[0160]

number

[0161] Using

[0162]

number

[0163] from

[0164]

number

[0165] Identify the encoding operator (U MUB Identified using )

[0166]

number

[0167] By identifying its characteristics, it is possible to generate measurement result data that reflects the characteristics of the dummy state.

[0168] The receiving node 120, based on the consistency between the encoded data and the measurement result data,

[0169]

number

[0170] A second verification can be performed on this. For example, the second verification can be determined to be successful if all the characteristics of the dummy state included in the measurement result data match the characteristics of the dummy state extracted from the encoded data. These characteristics may be related to the bias.

[0171] If the second verification fails, the receiving node 120 may determine that the third quantum state or other elements have been forged or tampered with due to an external attack such as interception in the middle, interrupt the subsequent process, and transmit a warning message to the sending node 110.

[0172] Meanwhile, if the receiving node 120 succeeds in the second verification, it determines that the third quantum state is normal and proceeds to the next process.

[0173] According to embodiments of this disclosure, it is possible to accurately determine whether or not an external attack such as a man-in-the-middle attack or eavesdropping has occurred during quantum communication, thereby improving the security of quantum communication. Furthermore, for verification purposes, a second quantum state including a dummy state is generated, and the encoded second quantum state is corrected for an uncorrectable error (E un By injecting a third quantum state to generate a third quantum state and using this third quantum state for quantum communication, the overhead of quantum communication can be minimized and security can be improved.

[0174] Furthermore, according to one embodiment of the present disclosure, since the quantum channel is verified based on the syndrome, it is possible to prevent the quantum state from being deformed through the unstable quantum channel.

[0175] The following describes how the transmitting node 110 transmits status information and data to the receiving node 120, with reference to Figures 3 and 4, and how the receiving node 120 verifies the status information, with reference to Figure 5.

[0176] Each method according to the embodiments described later is merely one example for achieving the objectives of this disclosure, and it goes without saying that some steps can be added or omitted as needed. Furthermore, the methods shown in Figures 3 to 5 can be performed by at least one processor included in the computing device. For convenience of explanation, the methods illustrated in Figures 3 to 4 will be described as being performed by the transmitting node 110 in Figure 1, and the method illustrated in Figure 5 will be described as being performed by the receiving node 120 in Figure 1.

[0177] Figure 3 is a flowchart illustrating a method by which a transmitting node generates state information and transmits it to a receiving node according to one embodiment of the present disclosure.

[0178] Referring to Figure 3, the transmitting node may determine one or more parameters based on the error rate of the quantum channel and generate a first quantum state using the determined one or more parameters (S301). According to one embodiment, the transmitting node may generate arbitrary k'-qubit information as the first quantum state.

[0179]

number

[0180] Any

[0181]

number

[0182] This can be expressed as shown in equation 1 above.

[0183] Next, the sending node will use a dummy state to improve security.

[0184]

number

[0185] A second quantum state can be generated by randomly mixing the two sets of states (S303). According to one embodiment, the transmitting node can acquire dummy states associated with mutually unbiased bases (MUBs) and generate a second quantum state by randomly mixing the acquired dummy states with the first quantum state. According to one embodiment, the transmitting node can generate a second quantum state by randomly mixing a first group of bits constituting a dummy state with a second group of bits constituting a quantum state and randomly mixing the dummy states with the first quantum state. For example, the transmitting node can acquire two sets of states based on randomly arranged mutually unbiased bases (MUBs).

[0186]

number

[0187] In relation to the k-k' length

[0188]

number

[0189] of

[0190]

number

[0191] can be randomly mixed.

[0192] [Number]

[0193] can be expressed by the above-mentioned Equation 2.

[0194] After that, after the sending node encodes the second quantum state, it can inject an uncorrectable error (E un ) into the encoded second quantum state to generate a third quantum state (S305). According to one embodiment, the sending node encodes the second quantum state based on one or more parameters related to a quantum error correction code (QECC), obtains an uncorrectable error, and then injects the obtained uncorrectable error into the second quantum state encoded based on the one or more parameters. For example, the uncorrectable error may include a Pauli error operator.

[0195] Next, the sending node can transmit the third quantum state to the receiving node (S307). According to some embodiments, the sending node can calculate the syndrome of the uncorrectable error (E un ) and transmit the calculated syndrome to the receiving node. The sending node can transmit the syndrome to the receiving node via a classical channel and transmit the third quantum state to the receiving node via a quantum channel.

[0196] FIG. 4 is a flowchart for explaining a method by which a sending node transmits data for verification to a receiving node according to an embodiment of the present disclosure. FIG. 4 can be performed after the method according to FIG. 3.

[0197] Referring to FIG. 4, the sending node can monitor whether a first acknowledgment message (Ack1) is received from the receiving node (S401). Here, the first acknowledgment message (Ack1) can be a message indicating that the third quantum state has been successfully received at the receiving node.

[0198] When the transmission node receives the first acknowledgment message (Ack1), it can transmit an uncorrectable error (E un ) to the receiving node (S403). At this time, the transmission node can transmit the uncorrectable error (E un ) to the receiving node using a classical channel. The receiving node can perform a first verification on the third quantum state using the uncorrectable error (E un ). Here, the first verification can be to determine whether the third quantum state has been forged or tampered with.

[0199] The transmission node can monitor whether the second acknowledgment message (Ack2) has been received from the receiving node (S405). Here, the second acknowledgment message (Ack2) can be a message indicating that the first verification of the third quantum state has been successful.

[0200] After that, when the transmission node receives the second acknowledgment message (Ack2) from the receiving node,

[0201] [Number]

[0202] and an encoding operator (U MUB ) for encoding zero auxiliary states into a state without mutual bias can be transmitted to the receiving node (S407). At this time, the transmission node

[0203] [Number]

[0204] and the encoding operator (U MUB ) can be transmitted to the receiving node via a classical channel.

[0205] FIG. 5 is a flowchart for explaining a method for verifying a quantum state at a receiving node according to an embodiment of the present disclosure.

[0206] Referring to FIG. 5, the receiving node can receive a quantum state from the transmitting node (S501). At this time, the receiving node can receive the quantum state from the transmitting node via a quantum channel. Here, the quantum state can be the above-mentioned

[0207]

Number

[0208] and so on. Furthermore, the receiving node can receive a syndrome from the transmitting node. According to one embodiment, the receiving node can receive the syndrome from the transmitting node via a classical channel.

[0209] Thereafter, the receiving node can extract a syndrome from the quantum state and perform verification on the channel by determining whether the extracted syndrome matches the received syndrome (S503). Here, the channel can be the state of the quantum channel.

[0210] The receiving node can determine whether the verification of the channel is successful (S505). The receiving node

[0211]

Number

[0212] If it is determined that the syndrome extracted from does not match the received syndrome (s), it can be determined that the channel is abnormal. When the receiving node determines that the channel is abnormal, based on the syndrome (s) received from the transmitting node via the classical channel,

[0213]

Number

[0214] error correction for can be performed (S506).

[0215] If the receiving node determines that error correction is successful or that the quantum channel is functioning correctly, it may transmit a first acknowledgment message (Ack1) to the transmitting node (S507).

[0216] The receiving node, in response to the transmission of the first acknowledgment message (Ack1), reports an uncorrectable error (E un ) can be received from the transmitting node (S509). According to one embodiment, an uncorrectable error (E un ) may include the Pauli error operator.

[0217] Subsequently, the receiving node may perform a first verification of the quantum state using the received syndrome (S511). Specifically, the receiving node may apply the received uncorrectable error to the quantum state to obtain a first syndrome, and then perform a first verification of the quantum state by determining whether the obtained first syndrome matches a predetermined second syndrome. According to one embodiment, the predetermined second syndrome may be an all-zero syndrome consisting of zero bits. In such a case, the receiving node may determine that the first verification was successful if the obtained first syndrome is an all-zero syndrome (i.e., the second syndrome).

[0218] If the receiving node succeeds in the first verification, it may transmit a second acknowledgment message (Ack2) related to the success of the first verification to the transmitting node (S513, S515).

[0219] After that, the receiving node

[0220]

number

[0221] and an encoding operator (U) for encoding the zero auxiliary states into unbiased states. MUB ) can be received from the transmitting node (S517).

[0222] Next, the receiving node

[0223]

number

[0224] and encoding operator (U MUB A second verification of the dummy state included in the quantum state can be performed using the encoding operator (U MUB ) using

[0225]

number

[0226] Encoding can be performed on the and encoded data can be generated.

[0227]

number

[0228] Measurement result data can be generated from the dummy states included. Here, the measurement result data reflects the characteristics of the dummy states, and the receiving node,

[0229]

number

[0230] Using

[0231]

number

[0232] from

[0233]

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[0234] Identify the encoding operator (U MUB Identified using )

[0235]

number

[0236] By identifying its characteristics, it is possible to generate measurement result data that reflects the characteristics of the dummy state.

[0237] The receiving node, based on the consistency between the encoded data and the measurement result data,

[0238]

number

[0239] A second verification can be performed. For example, the second verification can be determined to have been successful if all the characteristics of the dummy state included in the measurement result data match the characteristics of the dummy state extracted from the encoded data.

[0240] If the receiving node succeeds in the first and second verifications, it may perform a verification success process and then perform routines related to the verification success (S521, S523). For example, the verification success routine may involve transmitting the quantum state to another node, transmitting specific data to another node, or executing a predetermined program.

[0241] If the receiving node fails any of the channel verification, first verification, or second verification, it may perform routines related to the subsequent verification failure (S525). For example, the verification failure routine may involve transmitting an alarm message to surrounding nodes informing them that an external attack has occurred, transmitting a message indicating that the quantum channel is unstable, interrupting data transmission and reception over the quantum channel, or executing a predetermined security-related program.

[0242] On the other hand, one or more nodes can act as relay nodes to transmit quantum states to nodes located at greater distances.

[0243] Figure 6 illustrates a quantum communication system for long-distance transmission according to one embodiment of the present disclosure.

[0244] As shown in Figure 6, the quantum communication system may consist of multiple nodes 610, 620, 630, 640, and 650. Some of these nodes 610, 620, 630, 640, and 650 may operate as relay nodes that relay quantum states.

[0245] At least one of a classical channel and a quantum channel may be formed between each node. In some embodiments, only a classical channel may be formed between the first node 610 and the second node 620, and no quantum channel may be formed. In such cases, the third node 630, the fourth node 640, and the fifth node 650 act as relay nodes, and the quantum state can be transmitted to the second node 620. The solid lines in Figure 6 illustrate the quantum channel, while classical channels may be formed between all nodes.

[0246] Multiple nodes 630, 640, and 650, which perform the functions of relay nodes, can relay quantum states and transmit them to long-distance destinations. In addition, multiple nodes 630, 640, and 650 acting as relay nodes can perform error correction on quantum states.

[0247] In Figure 6, the first node 610 is a transmitting node that transmits quantum states, the second node 620 is a destination node for receiving quantum states, and the third node 630, fourth node 640, and fifth node 650 can operate as relay nodes. The number of relay nodes illustrated in Figure 6 is just an example, and the number of relay nodes can be changed.

[0248] In such a case, the first node 610 can generate a quantum state (the third quantum state in Figure 2) and transmit it to the third node 630. Furthermore, the first node 610 can broadcast the syndrome to all nodes 620, 630, 640, and 650 using a classical channel.

[0249] The third node 630 can perform verification of the quantum channel using the broadcasted syndrome. The third node 630 can perform error correction on the quantum state based on the syndrome.

[0250] Subsequently, the third node 630 transmits the quantum state to the fourth node 640, which verifies the quantum channel and, if necessary, can perform error correction on the received quantum state based on the syndrome.

[0251] The fourth node 640 can transmit the quantum state to the fifth node 650, which can then verify the quantum channel, perform error correction on the quantum state if necessary, and then transmit the quantum state to the second node 620.

[0252] The receiving node, the second node 620, may transmit a first acknowledgment message (Ack1) to the first node 610 if it successfully verifies the quantum channel or corrects errors in the quantum state. The first acknowledgment message (Ack1) may be transmitted to the first node 610 via the classical channel.

[0253] In such a case, the first node 610 will receive an uncorrectable error (E un ) can be transmitted to the second node 620 via the classical channel.

[0254] Subsequently, the second node 620 encountered an uncorrectable error (E un Using this method, a first verification of the quantum state can be performed, and if the first verification is successful, a second acknowledgment message (Ack2) can be transmitted to the first node 610 via the classical channel.

[0255] Next, the first node 610, in response to the second acknowledgment message (Ack2), uses a classical channel

[0256]

number

[0257] and encoding operator (U MUB ) can be transmitted to the second node 620.

[0258] Node 2, 620

[0259]

number

[0260] and encoding operator (U MUB Using this, a second verification of the dummy states included in the quantum state can be performed. If the first and second verifications are successful, the second node 620 may execute a predetermined subsequent process. On the other hand, if the first or second verification of the quantum state fails, the second node 620 does not execute a predetermined subsequent process.

[0261] As mentioned above, less overhead can be applied, and quantum states can be transmitted to nodes located at greater distances. In addition, verification of the channel formed with the node that transmitted the quantum state can be performed at each node, thereby improving the quality of quantum communication.

[0262] The hardware configurations of exemplary computing systems in several embodiments are described below with reference to Figure 7. The computing systems described with reference to Figure 7 refer to the transmitting and / or receiving nodes described above.

[0263] Figure 7 is an exemplary hardware configuration diagram showing how computing systems can be realized in various embodiments.

[0264] The computing system 1000 according to this embodiment may include one or more processors 1100, a system bus 1600, a communication interface 1200, a memory 1400 for loading computer programs 1500 performed by the processors 1100, and storage 1300 for storing the computer programs 1500. Figure 7 shows only the components associated with the embodiment. Therefore, a person of the ordinary skill in the art to which the embodiments of this specification belong will see that, in addition to the components shown in Figure 7, other general-purpose components may be included.

[0265] The processor 1100 can control the overall operation of each component of the computing system 1000. The processor 1100 may include at least one of a CPU (Central Processing Unit), an MPU (Micro Processor Unit), an MCU (Micro Controller Unit), a GPU (Graphic Processing Unit), or any form of processor known in the art herein. The processor 1100 may also perform calculations for at least one application or program to execute methods / operations according to various embodiments. The computing system 1000 may comprise two or more processors.

[0266] Memory 1400 stores various data, instructions, and / or information. Memory 1400 may load one or more programs 1500 from storage 1300 to perform methods / operations according to various embodiments herein. Examples of memory 1400 may be, but are not limited to, RAM. The system bus 1600 provides communication functions between components of the computing system 1000.

[0267] The bus 1600 can be implemented as various types of buses, such as an address bus, a data bus, and a control bus. The communication interface 1200 can connect to a communication network. The storage 1300 can non-temporarily store one or more computer programs 1500. The storage 1300 may consist of non-volatile memory such as flash memory, a hard disk, a removable disk, or any form of computer-readable recording medium known in the art to which the embodiments herein belong.

[0268] The computer program 1500 may include one or more instructions that implement the methods / operations according to various embodiments of this specification. When the computer program 1500 is loaded into memory 1400, the processor 1100 can execute the methods / operations according to various embodiments of this specification by having the one or more instructions execute. The computer program 1500 may include instructions for the methods according to various embodiments described with reference to Figures 1 to 6.

[0269] According to one embodiment, the computer program 1500 may include instructions for the operation of generating a second quantum state using a first quantum state and a dummy state, the operation of encoding the generated second quantum state, the operation of generating a third quantum state by injecting an uncorrectable error into the encoded second quantum state, and the operation of transmitting the generated third quantum state to a receiving node.

[0270] Additionally or alternatively, the computer program 1500 may include instructions for operations such as receiving a quantum state from a transmitting node, receiving an uncorrectable error from the transmitting node, applying the uncorrectable error to the quantum state to obtain a first syndrome, and determining whether the obtained first syndrome matches a predetermined second syndrome to perform a first verification of the quantum state.

[0271] In some embodiments, the computing system 1000 described with reference to Figure 7 can be configured using one or more physical servers included in a server farm based on cloud technology such as virtual machines. In this case, at least a portion of the components shown in Figure 7, namely the processor 1100, memory 1400, and storage 1300, may be virtual hardware, and the communication interface 1200 may also be composed of virtualized networking elements such as a virtual switch.

[0272] The various embodiments of this disclosure and the effects thereof have been described above with reference to Figures 1 to 7. The effects based on the technical concept of this disclosure are not limited to those described above, and other effects not described can be clearly understood by a person of the ordinary skill from the following description.

[0273] The above-described method according to embodiments of the present invention can be executed by running a computer program implemented as computer-readable code. The computer program can be transmitted from a first computing device to a second computing device via a network such as the Internet, and installed on the second computing device for use. Although the operations are shown in a specific order in the drawings, these operations do not necessarily have to be executed in the specific or sequential order shown, nor should they be understood as something that will only yield the desired result if all the shown operations are executed. In certain situations, multitasking and parallel processing may be advantageous.

[0274] While embodiments of this disclosure have been described above with reference to the attached drawings, a person with ordinary skill in the art to which this disclosure belongs will understand that the present invention can be carried out in other specific forms without altering the technical idea or essential features. Therefore, the above embodiments should be understood to be illustrative and not limiting in all respects. The scope of protection of this invention should be interpreted as defined in the claims, and all technical ideas within an equivalent scope should be interpreted as being included in the scope of rights of the technical idea as defined in this disclosure.

Claims

1. A method performed by a computing device, A step of generating a second quantum state using the first quantum state and a dummy state, The steps include encoding the generated second quantum state, The steps include: injecting an uncorrectable error into the encoded second quantum state to generate a third quantum state; A method for transmitting a quantum state, comprising the step of transmitting the generated third quantum state to a receiving node.

2. The step of generating the aforementioned second quantum state is: The steps include obtaining dummy states related to mutually unbiased bases, A method for transmitting a quantum state according to claim 1, comprising the step of randomly mixing the acquired dummy states with the first quantum state to generate a second quantum state.

3. The step of generating the aforementioned third quantum state is: The steps include encoding the second quantum state based on one or more parameters related to a quantum error correction code, The step of obtaining the aforementioned uncorrectable error, A method for transmitting a quantum state according to claim 1, comprising the step of injecting the acquired uncorrectable error into a second quantum state encoded based on one or more of the aforementioned parameters.

4. The steps include obtaining the syndrome of the aforementioned uncorrectable error, The method for transmitting a quantum state according to claim 1, further comprising the step of transmitting the acquired syndrome to the receiving node.

5. The computing device is A method for transmitting quantum states according to claim 4, comprising transmitting the syndrome to the receiving node via a classical channel and transmitting the third quantum state to the receiving node via a quantum channel.

6. After the step of transmitting the third quantum state to the receiving node, The method for transmitting a quantum state according to claim 1, further comprising the step of transmitting the uncorrectable error to the receiving node when a first acknowledgment message relating to the successful reception of the third quantum state is received from the receiving node.

7. After the step of transmitting the uncorrectable error to the receiving node, The method for transmitting a quantum state according to claim 6, further comprising the step of transmitting a permutation operator and an encoding operator for encoding the zero auxiliary states into an unbiased state to the receiving node when a second acknowledgment message relating to the successful verification of the third quantum state is received from the receiving node.

8. A method performed by a computing device, The stage of receiving the quantum state from the transmitting node, The step of receiving an uncorrectable error from the aforementioned transmitting node, The steps include applying the aforementioned uncorrectable error to the quantum state to obtain a first syndrome, A method for verifying a quantum state, comprising the step of determining whether the acquired first syndrome matches a predetermined second syndrome, and performing a first verification of the quantum state.

9. The aforementioned predetermined second syndrome is an all-zero syndrome, where the bits are all zero. The first step of performing the aforementioned quantum state is: The quantum state verification method according to claim 8, further comprising the step of determining that the first verification was successful if the obtained first syndrome is an all-zero syndrome.

10. Before the stage of receiving the aforementioned uncorrectable error, The step of receiving the syndrome from the aforementioned transmitting node, The method for verifying a quantum state according to claim 8, further comprising the step of verifying a quantum channel based on whether or not the syndrome extracted from the quantum state matches the received syndrome.

11. The step of receiving the aforementioned uncorrectable error is: If the verification of the quantum channel is successful, the first acknowledgment message indicating that the quantum state has been successfully received is transmitted to the transmitting node. The quantum state verification method according to claim 10, further comprising the step of receiving the uncorrectable error from the transmitting node as a response to the transmission of the first acknowledgment message.

12. The computing device is A method for verifying a quantum state according to claim 10, comprising receiving the syndrome via a classical channel and receiving the quantum state via a quantum channel.

13. If the first verification is successful, the transmission node receives an encoding operator for encoding the permutation operator and the zero auxiliary states into an unbiased state, The method for verifying a quantum state according to claim 8, further comprising the step of performing a second verification of dummy states included in the quantum state based on the permutation operator and the encoding operator.

14. The computing device is The method for verifying a quantum state according to claim 13, wherein the permutation operator and the encoding operator are received via a classical channel.

15. One or more processors, Includes memory for storing computer programs executed by one or more processors, The aforementioned computer program, The operation of generating a second quantum state using the first quantum state and a dummy state, The operation of encoding the generated second quantum state, The operation of injecting an uncorrectable error into the encoded second quantum state to generate a third quantum state, A computing system including instructions for an operation to transmit the generated third quantum state to a receiving node.

16. One or more processors, Includes memory for storing computer programs executed by one or more processors, The aforementioned computer program, The operation of receiving quantum states from the transmitting node, The operation of receiving an uncorrectable error from the aforementioned transmitting node, The operation of applying the aforementioned uncorrectable error to the quantum state to obtain the first syndrome, A computing system including instructions for performing a first verification of the quantum state by determining whether the acquired first syndrome matches a predetermined second syndrome.

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