KR101924100B1 - Method and Device of performing Quantum Key Distribution (QKD) among plurality of devices - Google Patents

Abstract

According to the present invention, a method of performing quantum key distribution (QKD) among plurality of devices, which is performed by a first device as a transmitting device, comprises: a qubit transmitting step of transmitting, by the first device, a first qubit or a second qubit to a second device, wherein the transmitted first and second qubit are stored in quantum memory of the second device; a qubit location announcing step of announcing, by the first device, the location of a pair of qubits entangled with the second device; and a measurement discrepancy announce reception step of receiving an announce about measurement discrepancy from the second device when the same bell state measurement on the pair of entangled qubits is not obtained.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for quantum key distribution among a plurality of devices,

The present invention relates to a method and apparatus for performing quantum key distribution. And more particularly, to a method and apparatus for performing quantum key distribution among a plurality of devices including an eavesdropper.

 Quantum Key Distribution (QKD) enables two remote parties to share a secret key. Most QKD schemes achieve security by sharing quantum signals prepared with two or more non-orthogonal bases. These typically include two bases; An arithmetic basis, and a Hadamard basis. In the operation base, a qubit has one of the following two states as shown in Equation (1).

The Hadamard basis is formed by the superposition of the above two states and has the form shown in Equation 2 below.

If measured with a Hadamard basis, the qubits prepared by the arithmetic base provide random results. This is an important uncertainty relationship and shows that the computational basis and the Hadamard basis are not commutated.

Entanglement is another quantum mechanical phenomenon that distinguishes quantum physics from classical physics. An entanglement-dependent QKD protocol for sharing the secret key has been proposed. An entangled system is typically comprised of one or more qubits and measures one of the system's qubits to provide some information about the other part of the system. For example, Equation 3 represents an entangled system of two cubits.

The correlation of the arithmetic base is explicit from the state, and a noteworthy feature of such a system is that there is correlation even when measured at any other basis.

The previously proposed QKD protocol has either a dependency on the uncertainty relationship for both security and actual transmission, or the use of entanglement in all shared qubits. The key is generated through correlation between the qubits and any disturbance in the correlation can indicate that eavesdropping is present. However, there is a problem in that both security and actual transmission are dependent on an uncertainty relationship or use entanglement in all shared qubits, so that it can be difficult to judge whether or not there is an eavesdropping due to a disturbance.

Therefore, a problem to be solved by the present invention is to perform quantum key distribution (QKD) among a plurality of devices.

In addition, a problem to be solved by the present invention is to detect eavesdropping by performing quantum key distribution (QKD) among a plurality of devices.

According to another aspect of the present invention, there is provided a method of quantum key distribution (QKD) between a plurality of devices, the method comprising: A first qubit transmitting a first qubit or a second qubit to a second device, wherein the transmitted first and second qubits are stored in the quantum memory of the second device; The first device announces the position of a pair of qubits entangled with the second device; And receiving a discontinuity announcement from the second device if the same Bell state measurement is not obtained for the pair of interlaced qubits.

In one embodiment, the first device transmits the first qubit at a probability p and transmits the second qubit at a probability of 1-p, and the first qubit is an individual qubit Lt; / RTI > At this time, the second qubit may be an entangled qubit, which corresponds to a half of the entangled 2-qubit system, and the other half may be transmitted before the second qubit or after a random number of individual qubits.

In one embodiment, after the qubit transmission process, a qubit status check process is performed to confirm that a certain number of individual qubits are shared between the first and second devices and that there is no entangled qubit before pending transmission .

In one embodiment, the qubit transmission process is repeated until the specific number of individual qubits are shared and there is no entangled qubit pending prior to transmission.

In one embodiment, a security key comparison process is performed to compare a subset of security keys with the second device to remove the possibility of a qubit swap from a third device attempting to eavesdrop on the air channel after the measurement discrepancy announcement process .

According to another aspect of the present invention, there is provided a method of performing quantum key distribution (QKD) between a plurality of devices, the method being performed by a second device that is a receiving device, A qubit receiving process for receiving a first qubit or a second qubit from the first device, wherein the received first and second qubits are stored in the quantum memory of the second device; A qubit location announcement reception step of receiving an announcement of a position of a pair of quadbits entangled with the first device from the first device; And a measurement inconsistency announcement process that notifies the first device of discrpancy if the same Bell state measurement is not obtained for the pair of entangled qubits.

In one embodiment, the first qubit is transmitted from the first device with a probability p, the second qubit is transmitted from the first device with a probability of 1-p, and the first qubit is computed using a random secure bit It may be a separate cubicle prepared at the base. At this time, the second qubit may be an entangled qubit, which corresponds to a half of the entangled 2-qubit system, and the other half may be transmitted before the second qubit or after a random number of individual qubits.

In one embodiment, after the qubit receiving process, a certain number of individual qubits are shared between the first and second devices, and the qubit receiving process is repeated until there is no entangled qubit pending in the first device It can be repeated.

In one embodiment, the measurement discrepancy announcement procedure may include performing an individual measurement on an operation basis for the first qubit corresponding to the individual qubits, A discrepancy can be judged.

In one embodiment, a security key comparison process is performed to compare a subset of security keys with the first device to remove the possibility of a qubit swap from a third device attempting to eavesdrop on the air channel after the measurement discrepancy announcement process .

In one embodiment, in the step of receiving the qubit, the stored first and second qubits are captured by the third device, measured by an operation base, and prepared again by a qubit according to the measured result, Lt; / RTI > transmitted back to the second device.

In one embodiment, in the step of receiving the qubit, the stored first and second qubits are captured by the third device, measured by an operation base, and prepared again by a qubit according to the measured result, Lt; / RTI > transmitted back to the second device.

In one embodiment, the third device may prepare its own qubit at state < RTI ID = 0.0 _> 0 > _E < / RTI > and perform a CNOT operation using the qubit that passes as the control qubit and its qubit as the target.

According to another aspect of the present invention, a first device that performs quantum key distribution (QKD) among a plurality of devices is a device that transmits a first qubit or a second qubit to a second device, Transmitting and receiving unit, wherein the transmitted first and second qubits are stored in the quantum memory of the second device; And announcing a position of a pair of quadbits entangled with the second device and if the same Bell state measurement is not obtained for the pair of entangled qubits, A control unit for controlling the quantum transceiver to receive an announcement for discrpancy and for comparing a subset of security keys with the second device to remove the possibility of a qubit swap from a third device to be eavesdropped in a public channel, . ≪ / RTI >

In one embodiment, the first device transmits the first qubit at a probability p and transmits the second qubit at a probability of 1-p, and the first qubit is an individual qubit Lt; / RTI >

In one embodiment, the second qubit is an entangled qubit, which corresponds to a half of the entangled 2-qubit system, and the other half may be transmitted before the second qubit or after a random number of individual qubits .

In one embodiment, the control unit determines whether a certain number of individual qubits are shared between the first and second devices, that there is no entangled qubit pending prior to transmission, and if the specific number of individual qubits are shared And controls the quantum transceiver to repeatedly transmit the first and second qubits until there is no entangled qubit that is pending before transmission.

A second device for performing quantum key distribution (QKD) among a plurality of devices according to another aspect of the present invention may be configured such that the second device transmits a first qubit or a second qubit Receiving a quantum transceiver; A quantum memory for storing the received first and second qubits; And receiving an announcement of the position of a pair of quadbits entangled with the first device from the first device and determining that the same Bell state measurement is obtained for the pair of entangled qubits, A subsystem for controlling the quantum transceiver to announce discrangement to the first device and to remove a possibility of qubit swapping from a third device to be eavesdropped in a public channel, And a control unit for comparing with the device.

In one embodiment, the first qubit is transmitted from the first device with a probability p, the second qubit is transmitted from the first device with a probability of 1-p, and the first qubit is computed using a random secure bit It may be a separate cubicle prepared at the base. At this time, the second qubit may be an entangled qubit, which corresponds to a half of the entangled 2-qubit system, and the other half may be transmitted before the second qubit or after a random number of individual qubits.

In one embodiment, the control unit controls the quantum transceiver to transmit the first and second quantized data to the first and second devices until a certain number of individual qubits are shared between the first and second devices, and there is no entangled qubit pending in the first device. It is possible to control to repeatedly transmit the second qubit. At this time, individual measurements may be performed based on the calculation of the first qubit corresponding to the individual qubits, and it may be determined whether the bell state measurement is inconsistent based on the individual measurements performed.

The method according to the present invention has an advantage that a unique QKD protocol using only one base can be used by performing quantum key distribution (QKD).

In addition, the method according to the present invention has the advantage of achieving security by measuring entanglement and bell state by performing quantum key distribution (QKD).

1 illustrates a quantum communication system for performing quantum key distribution among a plurality of devices in accordance with the present invention.
2 shows a detailed configuration of first and second devices corresponding to a transmitting or receiving device according to the present invention.
FIGS. 3A and 3B show a flow chart of a method of performing quantum key distribution (QKD) in a first device and a second device, respectively, according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It will be possible. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The term " and / or " includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

The suffix " module ", " block ", and " part " for components used in the following description are given or mixed in consideration of ease of specification only and do not have their own distinct meanings or roles .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, a method and apparatus for performing quantum key distribution (QKD) among a plurality of devices according to the present invention will be described. The present invention proposes a protocol using only one basis for exchanging qubits. The presence of an eavesdropper is detected using entanglement. The proposed scheme is proposed for intercept-retransmission attacks and controlled-NOT (CNOT) gate attacks as described below.

1 illustrates a quantum communication system for performing quantum key distribution among a plurality of devices in accordance with the present invention. As shown in FIG. 1, the quantum system includes a first device 100 and a second device 200 as a legitimate device for performing quantum communication, and a third device 300 acting as an eavesdropper .

For example, the first device 100 and the second device 200 can be used by users Alice and Bob. Also, the third device 300 can be used by the eavesdropper Eve. Alice can also send a quantum message and a classical message to Bob, the recipient, as the sender. A quantum channel is partially a secure channel and is vulnerable to tampering and swapping of messages. The existing channel is a public channel and all communication over the existing channel is available to the eavesdropper Eve. What legitimate objects, such as the first and second devices 200, are aiming to share a security key at the end of the protocol. On the other hand, Eve using the third device 300 is an eavesdropper and the goal is to steal many bits of possible security keys.

Next, let's take a closer look at the security of the proposed protocol. First, in an intercept-resend (IR) attack, the third device 300 captures a passing qubit, measures it with the operation base, prepares the qubit again according to the obtained result, And transmits it to the second device 200 again. The third device 300 will obtain an accurate value each time the passing qubit is a separate qubit. In the case of an entangled qubit, the third device 300 will cause disturbance, and the entangled state corresponds to Equation 4 below.

Where the subscripts represent the first or second half of the entangled system. The density operator of this perfect bipartite state corresponds to Equation 5 below.

In the case of an IR attack, the third device 300 performs measurements on half of the entangled system. The local state for any half of this tangled system is written as < EMI ID = 6.0 >

This corresponds to a maximally mixed single qubit state. Therefore, in measuring half of the entangled system, the third device 300 measures a single qubit in the maximally mixed state. The measurement result of the third device 300 is completely random and the third device 300 breaks the entanglement. When the second device 200 performs a bell state measurement on these two qubits, the second device 200 can acquire any bell states as a measurement result, thus informing the on-line tapping.

Next, let's take a closer look at the controlled-NOT (CNOT) attack. The controlled-NOT (CNOT) gate is defined by Equation (7) below.

Where a is the control qubit and b is the target cubic. The orientation of the subscripts is clearly as described above. The CNOT attack is given by Equation 8 below, and can thus also be referred to as entanglement attack.

In this representation, as a result of the application of the CNOT gate, the right qubit pair is entangled. During this attack, the third device 300 prepares its own qubit in state 0 > _E , and performs a CNOT operation using the qubit that passes as the control qubit and its qubit as the target. If the passing qubit is not entangled, this operation is equivalent to Equation (7). In the case where the qubit traverses a part of the entangled system, this operation is expressed as Equation (9) below.

Similarly, a CNOT attack on a second passing qubit provides a state as shown in Equation 10 below.

This state is the global state in which the first two cubes are held by the second device 200 and the second cubes are held by the third device 300. The state of the second device 200 is obtained by following the cubes of the third device 300, as shown in Equation (11) below.

From the state of Equation 11, it can be easily seen that the two qubit states held by the second device 200 are not entangled, but instead are a mixture of states | 00> ₁₂ and | 11> ₁₂ . This can be easily distinguished in an entangled state by performing a local measurement or a collective bell state measurement on two cubits with a Hadamard basis. In the case of individual measurements with a Hadamard basis, the probability that two cubits will be in the same state is one-half. Similarly, the bell state measurement results are the same probability | φ ⁺ > or | φ ^- >. In all cases, the existence of the third device 300 corresponding to the eavesdropper has been discovered, and the existence of such a third device 300 has been known to legitimate objects.

In the foregoing, a quantum communication system for performing quantum key distribution among a plurality of devices according to the present invention, a protocol for the quantum communication system, and security protocols for different attacks have been described. Hereinafter, a flow chart and a device configuration diagram of a method of performing quantum key distribution (QKD) between a plurality of devices according to the present invention will be described.

First, a configuration diagram of a quantum key distribution (QKD) between a plurality of devices will be described. In this regard, FIG. 2 shows a detailed configuration of first and second devices corresponding to a transmitting or receiving device according to the present invention. As shown in FIG. 2, the first device 100 may be a transmitting device and the second device 200 may be a receiving device, but the present invention is not limited thereto, and vice versa. The first device 100 includes a control unit 110, a quantum transceiver unit 120, and a memory 130. In addition, the transmitting device may further include a laser source 140. Meanwhile, the second device 200 includes a control unit 210, a quantum transceiver unit 220, and a memory 230. Here, the memories 130 and 230 may be general memory or quantum memory.

First, let's consider a quantum key distribution (QKD) performed by each component of the first device 100 corresponding to a transmitting device.

The quantum transceiver 120 transmits a first qubit or a second qubit to the second device 200. At this time, the transmitted first and second qubits may be stored in the quantum memory 230 of the second device 200.

The controller 110 announces the position of a pair of qubits entangled with the second device 200 and the same Bell state measurement is obtained for the pair of entangled qubits , And controls the quantum transceiver (120) to receive an acknowledgment for discrpancy from the second device (200). In addition, the control unit 110 compares a subset of the security keys with the second device 200 to eliminate the possibility of a cubit swapping from the third device 300 to be eavesdropped in the air channel.

At this time, the first device 100 transmits the first qubit at a probability p and transmits the second qubit at a probability of 1-p, and the first qubit is an individual qubit Lt; / RTI > Also, the second qubit may be a tangled qubit, which corresponds to half the tangled 2-qubit system, and the other half may be transmitted before the second qubit or after the individual qubits of a random number.

In addition, the controller 110 can confirm whether a specific number of individual qubits are shared between the first and second devices 100 and 200, and whether there is an entangled qubit that is pending before transmission. In addition, the controller 110 controls the quantum transceiver 120 to transmit the first and second qubits until the specific number of individual qubits are shared and there is no entangled qubit pending before transmission It is possible to control to repeat transmission.

Next, let us consider a quantum key distribution (QKD) performed by each component of the second device 200 corresponding to the receiving device.

The quantum transceiver 220 receives the first qubit or the second qubit from the first device 100 by the second device 200.

The quantum memory 230 stores the received first and second qubits.

The control unit 210 receives an announcement of the position of a pair of qubit that is entangled with the first device 100 from the first device 100. Also, if the same bell state measurement is not obtained for the pair of entangled qubits, the controller 210 controls the quantum transceiver (not shown) to inform the first device 100 of discrpancy 220). In addition, the control unit 210 compares a subset of the security keys with the second device 200 in order to eliminate the possibility of the cubit swapping from the third device 300 to be eavesdropped in the air channel.

At this time, the first qubit is transmitted from the first device 100 with a probability p, the second qubit is transmitted from the first device with a probability of 1-p, and the first qubit is calculated using an operation It may be a separate cubicle prepared at the base. Also, the second qubit may be a tangled qubit, which corresponds to half the tangled 2-qubit system, and the other half may be transmitted before the second qubit or after the individual qubits of a random number.

In addition, the controller 210 controls the first and second devices 100 and 200 so that a predetermined number of individual qubits are shared between the first and second devices 100 and 200 until there is no entangled qubit And control so that the quantum transceiver 220 repeatedly transmits the first and second qubits. In addition, the controller 210 performs individual measurement based on the calculation based on the first qubit corresponding to the individual qubits, and determines whether or not the bell state measurement is inconsistent based on the performed individual measurement .

Next, FIGS. 3A and 3B show a flowchart of a method of performing quantum key distribution (QKD) in the first device and the second device, respectively, according to the present invention.

3A, a method of performing quantum key distribution performed by a first device includes performing a qubit transmission process S110, a qubit status checking process S120, a cubit position announcement process S130, (S140), and a security key comparison process (S150).

In the qubit transmission process (S110), the first device transmits a first qubit or a second qubit to the second device. At this time, the transmitted first and second qubits are stored in the quantum memory of the second device. At this time, the first device may transmit the first qubit at a probability p and transmit the second qubit at a probability of 1-p, and the first qubit may be a separate qubit prepared by an operation base using a random security bit . On the other hand, the second qubit may be an entangled qubit, which corresponds to a half of the entangled 2-qubit system, and the other half may be transmitted before the second qubit or after a random number of individual qubits.

In the qubit state checking step (S120), it is confirmed whether a certain number of individual qubits are shared between the first and second devices, and whether there is an entangled qubit that is pending before transmission. Meanwhile, the qubit transmission process (S110) may be repeated until the specific number of individual qubits are shared and there is no entangled qubit pending before transmission.

In the qubit position announcement process (S130), the first device announces the position of a pair of qubits entangled with the second device.

If the same Bell state measurement is not obtained for the pair of entangled qubits in the measurement inconsistency announcement reception step S140, an annunciation for discrpancy is received from the second device .

In the security key comparison process (S150), a subset of the security key is compared with the second device to eliminate the possibility of a cubit swapping from a third device to be eavesdropped in a public channel.

Referring to FIG. 3B, the quantum key distribution method performed by the second device includes a qubit receiving process S210, a cubit position announcement receiving process S220, a measurement discrepancy announcement process S230, And a security key comparison process (S240).

In the qubit receiving process (S210), the second device receives a first qubit or a second qubit from the first device. At this time, the received first and second qubits may be stored in the quantum memory of the second device.

In the qubit position announce reception process (S220), an announcement is received from the first device regarding the position of a pair of qubits entangled with the first device.

If the same Bell state measurement is not obtained for the pair of entangled qubits in the measurement mismatch test procedure (S230), the first device announces discrangement.

On the other hand, the first qubit is transmitted from the first device with a probability p, the second qubit is transmitted from the first device with a probability of 1-p, and the first qubit is prepared with a calculation base using a random security bit It can be a separate qubit. Also, the second qubit may be a tangled qubit, which corresponds to half the tangled 2-qubit system, and the other half may be transmitted before the second qubit or after the individual qubits of a random number.

Meanwhile, after the qubit receiving process (S210), a certain number of individual qubits are shared between the first and second devices, and the qubit receiving process (S210) is repeated until there is no entangled qubit pending in the first device ) Can be repeated.

In the qubit receiving step (S210), the stored first and second qubits are captured by the third device and can be measured by an operation base. Also, it may be a qubit that is prepared again as a qubit according to the measured result, and is transmitted again from the third device to the second device. At this time, the entangled state due to disturbance caused by the third device can be determined as shown in Equation (4). On the other hand, the density operator related to the entangled state can be determined as shown in Equation (5).

Further, the third device may perform measurements on any half of the entangled system, and the entangled state for any half of the system may be determined to correspond to the maximally mixed single qubit state, as shown in equation (6).

On the other hand, in the measurement discrepancy estimation procedure (S230), individual measurements are performed on the basis of the calculation for the first qubit corresponding to the individual qubits, and a discrepancy Can be judged.

In this regard, the third device may prepare its own qubit in state < RTI ID = 0.0 _> 0 > _E , < / RTI > and perform a CNOT operation using its own qubit as a target and the qubit passing as a control qubit. At this time, the CNOT operation when the qubit passes through a part of the entangled system can be determined as shown in Equation (9). Further, the CNOT operation in the case where the qubit traverses a part of the system for a second time can be determined as shown in Equation (10). Also, by tracking the cubes of the third device, the state of the second device can be obtained as shown in Equation (11).

Meanwhile, in the security key comparison process (S240), a subset of the security key is compared with the first device in order to eliminate the possibility of the cubit swapping from the third device to be eavesdropped in the public channel.

As described above, a unique QKD protocol using only one base is proposed. Security is achieved by measuring entanglement and bell state. It is possible to change the fragment of the entangled qubit to change the detection probability of the eve.

According to at least one embodiment of the present invention, by performing quantum key distribution (QKD), it is possible to use a unique QKD protocol using only one base.

Also, according to at least one embodiment of the present invention, there is an advantage that security can be achieved by measuring entanglement and bell state by performing quantum key distribution (QKD).

According to a software implementation, not only the procedures and functions described herein, but also each component may be implemented as a separate software module. Each of the software modules may perform one or more of the functions and operations described herein. Software code can be implemented in a software application written in a suitable programming language. The software code is stored in a memory and can be executed by a controller or a processor.

100: first device 200: second device
300: Third device

Claims (19)

A method of performing quantum key distribution (QKD) between a plurality of devices, the method being performed by a first device that is a transmitting device,
Wherein the first device transmits a first qubit or a second qubit to a second device, wherein the transmitted first and second qubits are stored in the quantum memory of the second device;
The first device announces the position of a pair of qubits entangled with the second device; And
And a measurement inconsistency announcement reception step of receiving an announcement for discrpancy from the second device if the same Bell state measurement is not obtained for the pair of entangled qubits, How to perform key distribution. The method according to claim 1,
The first device transmits the first qubit at a probability p, the second qubit at a probability 1-p,
Wherein the first qubit is an individual qubit prepared by an operation base using a random security bit,
Wherein the second qubit is an entangled qubit corresponding to a half portion of an entangled 2-qubit system and the other half is transmitted before the second qubit or after individual qubits of a random number. 3. The method of claim 2,
After the qubit transmission process,
Further comprising a qubit condition check process for verifying that a certain number of individual qubits are shared between the first and second devices and that there are no entangled qubits pending prior to transmission. The method of claim 3,
Wherein the qubit transmission process is repeated until the specific number of individual qubits are shared and there is no entangled qubit pending prior to transmission. The method according to claim 1,
After the measurement discrepancy announcement reception process,
Further comprising a security key comparison step of comparing a subset of security keys with the second device to eliminate the possibility of a qubit swapping from a third device to be eavesdropped in the air channel. A method for performing quantum key distribution (QKD) between a plurality of devices, the method being performed by a second device that is a receiving device,
A qubit receiving process in which the second device receives a first qubit or a second qubit from the first device, the received first and second qubits being stored in the quantum memory of the second device;
A qubit location announcement reception step of receiving an announcement of a position of a pair of quadbits entangled with the first device from the first device; And
And a measurement inconsistency announcement process that notifies the first device of discrpancy if the same Bell state measurement is not obtained for the pair of entangled qubits. . The method according to claim 6,
Wherein the first qubit is transmitted from the first device with a probability p and the second qubit is transmitted from the first device with a probability of 1-p,
Wherein the first qubit is an individual qubit prepared by an operation base using a random security bit,
Wherein the second qubit is an entangled qubit corresponding to a half portion of an entangled 2-qubit system and the other half is transmitted before the second qubit or after individual qubits of a random number. The method according to claim 6,
After the qubit receiving process,
Characterized in that a predetermined number of individual qubits are shared between the first and second devices and the qubit receiving process is repeated until there is no pending qubit in the first device . 8. The method of claim 7,
The measurement discrepancy announcement process includes:
Wherein individual measurements are performed on an operation basis for the first qubit corresponding to the individual qubits and a discrepancy for the bell state measurement is determined based on the performed individual measurements. The method according to claim 6,
After the measurement discrepancy announcement process,
Further comprising a security key comparison step of comparing a subset of security keys with the first device to eliminate the possibility of a cubit swapping from a third device attempting to eavesdrop on the air channel. 1. A first device for performing quantum key distribution (QKD) between a plurality of devices,
A quantum transceiver transmitting a first qubit or a second qubit to a second device, wherein the transmitted first and second qubits are stored in the quantum memory of the second device;
Announce the location of a pair of quadbits entangled with the second device and if the same Bell state measurement is not obtained for the pair of entangled qubits, control unit for controlling the quantum transceiver to receive an announcement for a discrunity and discarding a possibility of qubit swapping from a third device to be eavesdropped in a public channel, Comprising a quantum key distribution device. 12. The method of claim 11,
The first device transmits the first qubit at a probability p, the second qubit at a probability 1-p,
Wherein the first qubit is an individual qubit prepared by an operation base using a random security bit,
Wherein the second qubit is a tangled qubit that is a half of an entangled 2-qubit system and the other half is transmitted before the second qubit or after individual qubits of a random number. 13. The method of claim 12,
Wherein,
Determining whether a specific number of individual qubits are shared between the first and second devices and that there is no entangled qubits pending prior to transmission and that the particular number of individual qubits are shared and are pending prior to transmission ) Controls the quantum transceiver to repeatedly transmit the first and second qubits until there is no entangled qubit. A second device for performing quantum key distribution (QKD) among a plurality of devices,
A quantum transceiver for receiving a first qubit or a second qubit from the first device;
A quantum memory for storing the received first and second qubits; And
Receiving an announcement of a position of a pair of quadbits entangled with the first device from the first device and obtaining the same Bell state measurement for the pair of entangled qubits , The control unit controls the quantum transceiver to announce a discrpancy to the first device and to transmit a subset of the security key to the second device in order to eliminate the possibility of qubit swapping from the third device to be eavesdropped in the public channel, And a control unit for comparing the quantized key distribution with the quantized key distribution. 15. The method of claim 14,
Wherein the first qubit is transmitted from the first device with a probability p and the second qubit is transmitted from the first device with a probability of 1-p,
Wherein the first qubit is an individual qubit prepared by an operation base using a random security bit,
Wherein the second qubit is a tangled qubit that is a half of an entangled 2-qubit system and the other half is transmitted before the second qubit or after individual qubits of a random number. 15. The method of claim 14,
Wherein,
A predetermined number of individual qubits are shared between the first and second devices, and the quantum transceiver repeats transmission of the first and second qubits until there is no entangled qubit pending in the first device Control,
Performing individual measurements on an operation basis for the first qubit corresponding to the individual qubits and determining whether the bell state measurement is inconsistent based on the performed individual measurements. 11. The method of claim 10,
In the qubit receiving process,
Wherein the stored first and second qubits are captured by the third device and measured by an operational basis and are again a qubit in the third device and transmitted back to the second device in accordance with the measured result ,
The entangled state due to the disturbance caused by the third device

Lt; / RTI >
The density operator associated with the entangled state,

Lt; / RTI >
How to perform quantum key distribution. 11. The method of claim 10,
In the qubit receiving process,
Wherein the stored first and second qubits are captured by the third device and measured by an operational basis and are again a qubit in the third device and transmitted back to the second device in accordance with the measured result ,
The entangled state due to the disturbance caused by the third device

Lt; / RTI >
The density operator associated with the entangled state,

Lt; / RTI >
The third device performs measurements on any half of the entangled system,
The entangled state for any half of

Such that the quantized key distribution is determined to correspond to a maximally mixed single qubit state. 11. The method of claim 10,
The third device prepares its own qubit at state < RTI ID = 0.0 _> 0 > _E , &_lt; / RTI > performs a CNOT operation using its own qubit as a target,
The CNOT operation when the qubit passes through a part of the entangled system

Lt; / RTI >
The CNOT operation when the qubit passes a part of the intertwined system a second time,

Lt; / RTI >
Tracks the cubes of the third device, and the state of the second device

, ≪ / RTI >

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