KR20230120217A - Delay unrelated data control system of quantum cryptography method - Google Patents

Abstract

The present invention relates to a delay-independent data control system in quantum cryptography. In the present invention, an optical signal generated by a laser diode is divided into a first optical signal, a second optical signal, and a third optical signal through a circulator, and the first optical signal is combined with SPAD1 through a second beam splitter, The second optical signal is transmitted through the delay line through the second beam splitter to the quantum channel through the first beam splitter, the third optical signal is combined with SPAD2, and the second beam splitter converts the reflected signal Bob connected to a light detector that detects and generates a reference waveform at the same time; and a Faraday mirror that reflects the second optical signal received through the quantum channel, and is divided into a first optical signal traveling to a circulator and a second optical signal traveling to a phase modulator through a beam splitter, The first optical signal is converted into an electrical signal in SPAD 1 (single photon detector) through the circulator, detects a single photon and is extinguished, and the second optical signal passes through an interferometer composed of a long path and a short path. , the signal incident to the polarization beam splitter is output in polarization and passes through the quantum channel. After the signal is phase-shifted by ∏/2 in Alice's Faraday mirror, the signal is reflected. The reflected signal passes through the storage line and modulates the intensity of the signal in the light intensity modulator. The signal whose intensity is modulated is attenuated to the level of a single photon in a variable optical attenuator, transmitted to a phase modulator, and modulated from the phase modulator.
The present invention has the effect of controlling optical elements and SPAD1 and SPAD2 in Bob from signals detected using a photodetector.

Description

Delay unrelated data control system of quantum cryptography method}

The present invention relates to a delay-independent data control system in quantum cryptography. More specifically, it relates to a delay-independent data control system in a quantum cryptography method in which a constant criterion is always generated even if a quantum channel is variable.

In general, a cryptographic key distribution (QKD) is a device that supplies a cryptographic key made of quantum to a communication network for data encryption. In other words, by utilizing the characteristics of quantum (quantity) to create an encryption key that cannot be hacked by a third party and distribute it to the sender and the receiver at the same time.

Quantum encryption key distribution systems that provide encryption keys necessary to encrypt important data are mainly used in public networks, government networks, and financial networks where security is important.

The quantum cryptographic key distribution technology is a technique for distributing and sharing cryptographic keys among remote users by using quantum mechanical properties of photons. When an attacker attempts to obtain cryptographic key information being distributed among users, quantum mechanical phenomena occur. This allows users to detect the presence of an attacker and respond to the attack.

More specifically, for example, in the quantum cryptographic key distribution system, the sender (Alice) and the receiver (Bob) usually exchange information for quantum cryptographic key distribution using a single photon, and at this time, the photon has polarization, phase, etc. The encryption key is distributed safely from the attack of the attacker (Eve) by using the characteristics of

However, when a hacking attempt by the attacker Eve occurs, the Quantum Bit Error Rate (QBER) increases in the receiver Alice and the transmitter Bob, and through this, it is determined that there is an attempt to hack. will do

The plug-and-play cryptographic key distribution structure that goes through this procedure is IM (Light Intensity Modulator), PM (Phase Modulator), VOA (Variable Optical Attenuator) must be operated, and it is difficult to control the optical element because the position point of the returned optical signal cannot be known from the Bob equipment.

In addition, when the single optical signal detected by the sender (Alice) is reflected from the receiver (Bob) and returns, if the length of the quantum channel is variable, the final destination SPAD (Single Photon Detector) There was a problem that it was difficult to operate in gate mode. That is, if the exact timing is not calculated, the SPAD cannot be properly operated. Therefore, there was a need to operate the SPAD according to the exact time when the signal exists, that is, the timing.

Korean Patent Publication No. 2020-0080708 Korean Patent Publication No. 2016-0038639 Korean Patent Publication No. 2010-0073042

Therefore, in order to solve this problem, the present invention is based on a photo detector of Alice (transmitter) and a photo detector of Bob (receiver), in a quantum cryptography method that can always control the delay time of a signal to be constant. It is an object to be able to provide a data control system independent of delay.

In addition, for the purpose of providing a delay-independent data control system in a quantum cryptography method capable of detecting an optical signal from a SPAD (single photon detector) at a certain timing even if the quantum channel acts as a variable variable do.

In order to solve this problem, the present invention is a delay-independent data control system in a quantum cryptography method, in which an optical signal generated from a laser diode passes through a circulator, and the optical signal is input to a second beam splitter to divide , Half passes through the phase modulator and delay line, passes through the polarization beam splitter, and the other half passes through the polarization beam splitter, and when input to the first beam splitter, is converted into two optical signals separated in time and transmitted to the quantum channel. Bob and a Faraday mirror that reflects the optical signal received through the quantum channel, and is branched into a first optical signal traveling to a circulator through a beam splitter and a second optical signal traveling to a phase modulator, The first optical signal is converted into an electrical signal to the photodetector through the circulator to control the phase modulator, variable optical attenuator, and light intensity modulator based on the incident time, and at the same time, another laser diode receives the optical signal. The second optical signal is phase-modulated through the phase modulator, and the Faraday mirror via a storage line through a variable optical attenuator that attenuates the phase-modulated second optical signal to a single photon level. It is characterized in that it includes Alice, which is reflected as it arrives and transmits to the Bob through the quantum channel again.

Also, the variable optical attenuator attenuates the second optical signal into a single photon.

In addition, an optical detector that detects an optical signal returning to Bob through the quantum channel and generates a reference waveform is connected to and formed from the first beam splitter of Bob.

The optical intensity modulator is formed between the variable optical attenuator and the delay line, and changes the intensity of the second optical signal.

Further, an SPAD1 connected to the second beam splitter and detecting an optical signal from a pulse divided by the second beam splitter is further provided.

In addition, it is characterized in that a SPAD2 connected to the circulator and detecting the optical signal received from Alice through the circulator is further provided.

Therefore, the present invention can operate the SPAD (Single Photon Detector) according to the precise timing at which the signal exists, so that even if the quantum channel acts as a variable variable, the SPAD can detect the optical signal at a certain time. It has the effect of providing a data control system independent of delay in the encryption method.

1 is a simplified configuration diagram of a delay-independent data control system in a quantum cryptography method according to the present invention.
2 is an overall configuration diagram of a delay-independent data control system in a quantum cryptography method according to an embodiment of the present invention.
3 is an interferometer table showing numerical changes of SPAD1 and SPAD2 according to the phase transformation of Bob and Alice.
4 is a flowchart of a quantum cryptographic key distribution method from the viewpoint of a transmitter (Alice) using phase modulation.
5 is a flowchart of a quantum cryptographic key distribution method from the perspective of a receiver (Bob) using phase modulation.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings.

In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In addition, since the terms used in this application are only used to describe specific embodiments, it is not intended to limit the present invention, and it is clear in advance that a singular expression also means a plurality of expressions unless the context clearly indicates otherwise. want to leave

1 is a simplified configuration diagram of a delay-independent data control system in a quantum cryptography method according to the present invention, and FIG. 2 is an overall configuration diagram of a delay-independent data control system in a quantum cryptography method according to an embodiment of the present invention. , Figure 3 is an interferometer table showing the numerical change of SPAD1 and SPAD2 according to the phase transformation of Bob and Alice, Figure 4 is a flow chart of a quantum encryption key distribution method from the viewpoint of the transmitter (Alice) using phase modulation, Figure 5 Is a flow chart of a quantum cryptographic key distribution method from the perspective of the receiver (Bob) using phase modulation.

Prior to explaining the present invention, the delay-independent data control system in the quantum cryptography method in this specification uses polarization coding or phase coding, and various quantum cryptosystems using one or more single photon detectors (SPAD). refers to For example, the data control system in this specification is a two-way or plug-and-play quantum cryptography system.

Here, in the two-way or the plug-and-play quantum cryptographic key distribution system, the optical signal starts from Bob (receiver), passes through Alice (transmitter), and then measures the photon signal transmitted to Bob with a photon detector (PAD). is a plug-and-play system.

This bidirectional photon system has the advantage of automatically correcting polarization or phase, and controls one control element to stabilize the quantum cryptosystem, that is, to synchronize photon arrival time and gate pulse arrival time to the photon detector. It is characterized in that only control for After being reflected from the Faraday mirror formed in the transmitter Alice, the polarization is converted to vertical, the time delay between the two pulses disappears, and interference occurs, so phase and polarization correction are not required.

As shown in FIG. 1, the approximate configuration of the delay-independent data control system in the quantum cryptography method according to an embodiment of the present invention includes Alice 200 as a transmitter, Bob 100 as a receiver, and a quantum channel (Fig. code is omitted), and the Alice 200 and the Bob 100 generate and share a quantum encryption key while exchanging optical signals through the quantum channel. In addition, it may be configured using various devices capable of generating and sharing quantum cryptographic keys to perform communication.

More specifically, in the delay-independent data control system in the quantum cryptography method of the present invention, the Alice (200) modulates and transmits information for generating a quantum cryptographic key to an optical signal, and the Bob (100) 200) to receive the transmitted optical signal.

In addition, the quantum channel is provided between the Alice 200 and the Bob 100 to transmit an optical signal. The quantum channel may be configured using an optical fiber, but the present invention is not necessarily limited thereto, and any other medium or medium capable of transmitting an optical signal may be used to configure the quantum channel. Accordingly, the Alice (200) and the Bob (100) exchange information necessary for generating a quantum cryptographic key using the phase (phasor), polarization (polarization), etc. of the optical signal using the BB84 protocol, and quantum cryptography It is possible to generate and share a key, and furthermore, by performing encryption and decryption using the generated quantum cryptographic key to perform confidential communication, it is possible to enhance the security of the communication system.

Hereinafter, with reference to FIG. 2, a description will be given of the configuration of a delay-independent data control system in the quantum cryptography of the present invention.

First, Bob 100 includes a first beam splitter 110, a light detector 120, a polarization beam splitter 130, a phase modulator 140, a second beam splitter 150, a circulator 160, and a laser diode. (170), SPAD1 (180) and SPAD2 (190).

The overall role of Bob 100 is to split the optical signal by inputting it to the second beam splitter 150, pass through the phase modulator 140 and the delay line 145, pass through the polarization beam splitter 130, The remaining light passes through the polarization beam splitter 130, is combined with the first beam splitter 110, and is split into two optical signals and transmitted to the Alice 200 through the quantum channel.

The first beam splitter 110 of Bob 100 is connected to and formed with an optical detector 120 that detects an optical signal reflected to Bob 100 through the quantum channel and simultaneously generates a reference waveform.

Hereinafter, the configuration of the Bob (100) will be described. The order of description of the components will be the order of operation of the two-way quantum cryptographic key distribution system of the present invention.

The laser diode 170 generates an optical signal that is a light pulse. The optical signal generated as described above is received by the circulator 160 .

The second beam splitter 150 equally splits the optical signal applied from the radar diode 170 in a 50:50 ratio, so that half passes through the delay line 145 and the long path path takes more time and the other half passes through the delay line 145. It is applied as a short path that goes straight to the direct polarization beam splitter (130: PBS). Here, the signal passing through the short path is referred to as a first optical signal. For reference, both the short path and the long path are referred to as an interferometer, which will be described later.

The phase modulator 140 serves to modulate the phase of the optical signal entering the long path. Here, the signal passing through the long path is referred to as a second optical signal. In addition, the addition of the delay line 145 makes the path longer than the above-mentioned short path, so the optical signal is delayed.

A polarization beam splitter (PBS) 130 outputs the first optical signal with a first polarization (eg, vertical polarization) and outputs the second optical signal with a second polarization (eg, horizontal polarization). do. That is, the polarization beam splitter 130 (PBS) is configured to split the input signal light into two polarizations whose polarization directions are orthogonal to each other.

The first beam splitter 110 further divides the first optical signal and the second optical signal transferred from the polarization beam splitter 130 in a ratio of 50:50 to the Alice 200 corresponding to the transmitter through the quantum channel. is to transmit

In addition, SPAD2 (190) detects a single photon received from Alice (200) through circulator (160). Then, the SPAD1 180 detects an optical signal from the pulses divided by the second beam splitter 150 .

For reference, the SPAD1 (180) and the SPAD2 (190) are single photon detectors. The single photon detector is a chip implemented with an ultra-sensitive optical sensor capable of detecting photons, the smallest unit of light. Since the pattern cannot be read, it is an essential component of quantum cryptographic communication that can make communication equipment that cannot be eavesdropped or intercepted.

Hereinafter, an overall description of Alice 200 will be given.

The Alice 200 includes a Faraday mirror 250 that reflects the optical signal received through the quantum channel, and divides the optical signal 50:50 through the beam splitter 210 and sends half of the optical signal to the circulator 260. The other half of the traveling first optical signal is branched into a second optical signal traveling to the phase modulator 220 .

The first optical signal is converted into an electrical signal in the photodetector 280 through the circulator 260 and extinguished, and the phase modulator 220 and The variable light attenuator 230 and the light intensity modulator 240 are controlled.

Meanwhile, the phase of the second optical signal is modulated through the phase modulator 220, and the storage line 245 is passed through a variable optical attenuator 230 that attenuates the phase-modulated second optical signal to a single photon level. ), it is reflected while reaching the Faraday mirror 250, and is retransmitted to Bob 100 through the quantum channel through the phase modulator 220.

Hereinafter, the configuration of Alice 200, which is a transmission unit, will be described in detail.

Alice 200 includes a beam splitter 210, a phase modulator 220, a variable optical attenuator 230, an optical intensity modulator 240 as a signal strength changing device, a storage line 245, a Faraday mirror 250, and a circulator. 260, a laser diode 270, and a photodetector 280.

As described above, the beam splitter 210 splits the optical signal transmitted from Bob 100 50:50, transmits half of the first optical signal toward the circulator 260, and half transmits the optical signal to the phase modulator. The second optical signal is transmitted in the (220) direction.

The circulator 260 transmits a first optical signal to an optical detector 280, and the optical detector 280 detects the optical signal received from the circulator 260. At the same time, the optical detector 280 controls the phase modulator 220 , the variable optical attenuator 230 and the optical intensity modulator 240 . And, the laser diode 270 emits an optical signal to generate a reference signal of Bob (100).

The phase modulator 220 modulates the second optical signal, and the variable optical attenuator 230 serves to attenuate the divided second optical signal to a single photon level.

The light intensity modulator 240 (light intensity modulator) serves to attenuate or enhance the waveform of the signal received in the second optical signal.

The storage line 245 is applied as a method for reducing noise of a quantum channel when the second optical signal propagates. Here, the role of the storage line 245 is that when photons are reflected or incident by the Faraday mirror 250, back scattering occurs when photons collide with each other instead of in the direction in which the photons travel. It causes noise, and it is applied as a method to reduce this phenomenon.

The Faraday mirror 250 reflects the second optical signal that has passed through the phase modulator 220, the variable optical attenuator 230, and the optical intensity modulator 240 and returns it to the phase modulator 220 in reverse order. will be.

Hereinafter, the operational relationship of the delay-independent data control system in the quantum cryptography method according to the present invention will be described.

First, the laser diode 170 of Bob 100 becomes a source for generating a laser light signal. An optical signal is generated by receiving a signal from a controller (not shown) that controls the laser diode 170 .

The laser light signal used in the delay-independent data control system in the quantum cryptography method of the present invention is a beam having a wavelength of about 1,550 nm. The optical signal, which is the beam, is generated by the laser diode 170, passes through the circulator 160, and is split 50:50 by a second beam splitter (150).

The pulse split as described above passes through the phase modulator 140 and the delay line 145 and passes through a long path to reach the polarization beam splitter 130 (PBS), and the other one passes through the second beam splitter 150 to the polarization beam splitter. It is transmitted to the quantum channel, which is an optical fiber, through a short path that reaches directly to (130). At this time, there is a difference between a pulse passing through a short path and a pulse passing through a long path by a delay between physical elements.

The optical signals, which are the two polarized signals, pass through the first beam splitter 110 and pass through the quantum channel to enter the Alice 200. : Divided by 50, half is incident in the direction of the circulator 260, and the remaining optical signal is transmitted in the direction of the Faraday mirror 250.

Among the divided optical signals, an optical signal incident in the direction of the circulator 260 is detected by the photodetector 280 and changed into an electrical signal, and the changed electrical signal is transmitted to a controller (not shown).

This transmitted signal is a reference for controlling the phase modulator 220, the variable optical attenuator 230, the light intensity modulator 240, and the Faraday mirror 250 corresponding to optical elements, which are internal components of the Alice 200. It becomes a signal. A pattern signal, which is a kind of synchronization signal, is transmitted to Bob (100) by laser transmission from the reference signal. The optical signal detected by the optical detector 280 synchronizes clocks between Bob 100 and Alice 200.

That is, the signal transmitted from Bob 100 is detected by the light detector 280, and the detected signal is used as a synchronization signal between Bob 100 and Alice 200. Based on the signal, the laser diode 270 of Alice 200 transmits an optical signal, and the transmitted signal passes through the circulator 260 and the beam splitter 210 in Alice 200 and passes through the quantum channel. The passed signal passes through the first beam splitter 110 in Bob 100 and is detected by the photodetector 120.

Meanwhile, the remaining optical signals going to the phase modulator 220 are transmitted in the order of the phase modulator 220, the variable optical attenuator 230, the light intensity modulator 240, and the Faraday mirror 250, the Faraday mirror ( 250), the polarization direction is rotated by ∏/2, and the components pass through the beam splitter 210 in the reverse order of the traveling direction of the components.

In addition, the phase is shifted by ∏/2 in the Faraday mirror 250 and reflected, and phase modulated by 0, ∏/2, ∏, and 3/2∏ through the phase modulator 220.

In this way, the previous signal to the beam splitter 210 in the Alice 200 can be controlled so that the phase modulator 220 and the light intensity modulator 240 are suitable for each timing.

In this way, the laser signal transmitted from Alice 200 through the above process is received through the quantum channel, and the laser signal is received from the photodetector 120 branched from the first beam splitter 110 of Bob 100. The received signal is made into an internal reference signal. However, the signal entering the first beam splitter 110 through the quantum channel is very weak, making it difficult for the photodetector 120 to detect it.

Accordingly, the optical signal that has passed through the first beam splitter 110 is simultaneously split into a long path and a short path through the polarization beam splitter 130 (PBS).

As for the classification of the path, the optical signal that was initially transmitted as a short path starting from Bob (100) passes through the Faraday mirror 250 of Alice (200) and returns to Bob (100), and the optical signal is incident as a long path. That is, they proceed in the opposite direction to the path initially taken by Bob (100).

Furthermore, the phase modulator 140 of the long path receiver 100 performs phase modulation by 0, ∏/2, and interferes through the second beam splitter 150.

Through both paths, they are merged in the second beam splitter 150 corresponding to the ends of both paths. The combined signal interferes, and the implemented signal is converted into an optical signal by SPAD1 (180) and SPAD2 (190) and detected.

As such, Alice 200 always controls the optical elements based on the timing at which the photodetector 280 detects the optical signal transmitted from Bob 100, and the photodetector 120 of BOb 100 Optical devices such as the polarization beam splitter 130 and the phase modulator 140 control the SPAD1 180 and the SPAD2 190 from the point of time when the optical signal transmitted from the Alice 200 is detected, and the quantum channel is variable. , the SPAD1 (180) and the SPAD2 (190) operate at a constant time from the photodetector 120 as reference points of time.

Therefore, according to the variable length of the quantum channel, the structure was changed from a quantum cryptographic key distribution system without a reference point to a structure with a reference point. Based on the photodetector 280 of (200) and the photodetector 120 of Bob (100), there is an excellent function that can automatically control the delay time of the signal always constant.

Hereinafter, an interferometer will be described with reference to the drawings.

Referring to FIG. 3, both the short path and the long path described above are referred to as an interferometer. The interferometer controls the values of the phase modulators 140 and 220 of Bob (100) and Alice (200) to obtain SPAD 1 (180) or SPAD 2 (190) is the system detected.

As shown in the table of FIG. 3, the phase modulators 140 and 220 are devices that perform phase modulation by voltage control, and as the phase value of the phase modulators 140 and 220 is set by voltage, SPAD1 (180 ) and a single photon is detected in SPAD2 (190).

The phase of the optical signal can be changed by applying a constant voltage to the phase modulators 140 and 220 . The phase-changed optical signal passes through Bob's (100) short path and long path and is detected by SPAD1 (180) and SPAD2 (190).

Hereinafter, with reference to FIGS. 4 and 5, a description will be given of a method for distributing quantum encryption keys in the transmitter 200 as Alice and the receiver 100 as Bob using phase modulation.

First, FIG. 4 shows a flowchart of a quantum cryptography key distribution method from the perspective of the transmitter 200 using phase modulation. As shown, in the quantum cryptography key distribution method from the perspective of the transmitter 200 using phase modulation, the transmitter 200 distributes the quantum cryptography key to the receiver 100 using a laser pulse, which is a series of light pulses. As a method, it may be configured to include a light pulse transmission step (S 10) and a verification information transmission step (S 20).

Furthermore, as a method of distributing a quantum cryptographic key from the perspective of the transmitter 200 using phase modulation, the transmitter 200 uses some or all of the information on the quantum cryptography key included in the series of light pulses Calculating a quantum cryptographic key (S 30) may be further included.

Referring to FIG. 4 in detail, first, in the light pulse transmission step (S10), the transmitter 200 randomly modulates each light pulse, i.e., a laser pulse, into one of a plurality of predetermined phases, and transmits the light pulse to the receiver 120.

For example, the transmitter 200 may randomly modulate a series of light pulses into one phase among 0, π/2, π, and 3/2π, and transmit the light pulses to the receiver 100 through a quantum channel.

Subsequently, in the verification information transmission step (S20), the transmission unit 200 transfers information on successive light pulses among the series of light pulses to the reception unit 100, and uses the measurement values for the successive light pulses. In the process of transmitting the series of light pulses, it is verified whether or not Eve, an attacker, has eavesdropped.

For example, when the continuous light pulses have the same phase, the continuous light pulses should be detected only by the photodetector 120 of the receiving unit 100, but when Eve, an attacker, intervenes , Photon can be detected not only by the photodetector 120 but also by the photodetector 280 on the side of the transmitter 200, as the same phase is not maintained and has various phases probabilistically.

However, when consecutive light pulses have the same phase, photons are detected only by the light detector 120 of the receiver 100 unless Eve, the attacker, eavesdrops.

However, at this time, when Eve approaches and eavesdrops on the continuous light pulse, the probability of detecting a photon in the photodetector 120 in the receiver 100 and the photon in the photodetector 280 in the transmitter 200 Since the probability of being detected is all 1/2, the detection result varies depending on whether or not the attacker Eve eavesdropped, so that the receiving unit 100 can clearly determine whether Eve is attacking.

5 is a flowchart of a quantum cryptographic key distribution method from the perspective of the receiving unit 100 using phase modulation. That is, it is the opposite viewpoint to that described in FIG. 4 .

As shown, the quantum cryptographic key distribution method from the perspective of the receiver 100 using phase modulation is a method in which the receiver 100 receives a quantum cryptographic key using a series of light pulses received from the transmitter 200. , light pulse receiving step (S 110) and eavesdropping verification step (S 120).

Furthermore, in the quantum cryptographic key distribution method from the perspective of the receiver 120 using phase modulation, the receiver 100 uses some or all of the information on the quantum cryptographic key included in the series of light pulses to obtain a quantum cryptographic key. A step of calculating (S 130) may be further included.

Therefore, through the quantum cryptographic key distribution method through FIGS. 4 and 5, it is possible to clearly detect eavesdropping of Eve corresponding to the attacker, thereby further improving security.

Those skilled in the art to which the present invention pertains as described above will understand that it can be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the above-described embodiments are illustrative and not limiting.

The scope of the present invention is indicated by the appended claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention. do.

100: Bob (receiver) 110: first beam splitter
120: photo detector 130: polarization beam splitter
140: phase modulator 145: delay line
150: second beam splitter 160: circulator
170: laser diode 180: SPAD 1
190: SPAD 2 Eve: Attacker
200: Alice (transmitter) 210: beam splitter
220: phase modulator 230: variable optical attenuator
240 light intensity modulator 245 storage line
250: Faraday mirror 260: circulator
270: laser diode 280: photodetector

Claims (6)

In a data control system independent of delay in quantum cryptography,
The optical signal generated by the laser diode 170 is passed through the circulator 160, and the optical signal is input through the second beam splitter 150 to be split, and half of the optical signal is transmitted through the phase modulator 140. ) and the delay line 145, pass through the polarization beam splitter 130, and 1/2 of the optical signal passes through the polarization beam splitter 130 and is incident on the first beam splitter 110. A receiving unit (Bob) 100 that converts two optical signals and transmits them through a quantum channel; and
It has a Faraday mirror 250 that reflects the optical signal received through the quantum channel, and the first optical signal traveling to the circulator 260 via the beam splitter 210 and the phase modulator 220 It is divided into a second optical signal, and the first optical signal is converted into an electrical signal to the photodetector 280 through the circulator 260, and the phase modulator 220, the variable optical signal based on the incident time The attenuator 230 and the light intensity modulator 240 are controlled, and at the same time, the laser diode 270 emits an optical signal to make a reference signal of the receiver Bob 100, and the second optical signal is transmitted to the phase modulator. The phase is modulated through 220 and reaches the Faraday mirror 250 through the storage line 245 through the variable optical attenuator 230 that attenuates the phase-modulated second optical signal to a single photon level. A data control system independent of delay in the quantum cryptography method, characterized in that it includes; a transmitter (Alice) 200 that is reflected and transmitted to the receiver (Bob) 100 through the quantum channel again.
According to claim 1,
The variable optical attenuator 230 attenuates the second optical signal into a single photon.
The method of claim 1, wherein the first beam splitter 110 of the receiver 100 includes an optical detector 120 that detects an optical signal returning to the receiver 100 through the quantum channel and generates a reference waveform at the same time. A data control system independent of delay in quantum cryptography, characterized in that it is connected and formed.
According to claim 1,
The optical intensity modulator 240 is formed between the variable optical attenuator 230 and the delay line 245 to change the intensity of the second optical signal. data control system.
According to claim 1,
A SPAD 1 (180) connected to the second beam splitter 150 and detecting an optical signal from a pulse split by the second beam splitter 150 is provided, regardless of delay in the quantum cryptography method, characterized in that A data control system.
According to claim 1,
Characterized in that a SPAD 2 (190) connected to the circulator 160 and detecting an optical signal received from the transmitter 200 through the quantum channel through the circulator 160 is further provided Delay-independent data control system in quantum cryptography.

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