CN112511300B - Continuous variable quantum key distribution system and method based on differential phase shift - Google Patents
Continuous variable quantum key distribution system and method based on differential phase shift Download PDFInfo
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Abstract
The invention discloses a continuous variable quantum key distribution system based on differential phase shift, which comprises a quantum key sending end, an optical fiber channel and a quantum key receiving end, wherein the quantum key sending end is connected with the optical fiber channel; the quantum key sending end generates pulse laser, and the modulated quantum signal is obtained after random phase modulation and signal attenuation are carried out; the optical fiber channel transmits the quantum signal to a quantum key receiving end; the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on a received signal, extracts local oscillation light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing. The invention also discloses a method of the continuous variable quantum key distribution system based on the differential phase shift. The invention applies the differential phase shift method of discrete quantum variable quantum key distribution to the distribution of continuous variable quantum key, so that the quantum key distribution process has high reliability, better performance, low cost and convenient implementation.
Description
Technical Field
The invention particularly relates to a continuous variable quantum key distribution system and method based on differential phase shift.
Background
At present, communication develops very rapidly in China, and a large number of communication systems cannot be separated in production and life; and the traditional communication mode is easy to steal information by the outside, and the secret-related requirements of protecting personal privacy, commercial confidentiality, technical secrecy and the like cannot be met. Therefore, information security is increasingly important in current social development.
One of the most important, and unique, properties of quantum key distribution is: if a third party attempts to eavesdrop on the password, both parties to the communication will perceive it. This property is based on the fundamental principle of quantum mechanics: any measurement of a quantum system will cause interference to the system. A third party attempting to eavesdrop on the password must somehow measure it, and these measurements can cause a noticeable anomaly. Information is transmitted through a quantum superposition state or a quantum entanglement state, and a communication system can detect whether eavesdropping exists or not. Quantum communication and its security are receiving wide attention from all the world of society. Quantum key distribution is the most secure in current communication schemes.
Continuous variable quantum key distribution is used as an important implementation mode of quantum cryptography communication, and has the advantages of high key generation rate, low implementation cost, convenience in deployment and the like. Especially, the quantum signal fusion device has the capability of being fused with the existing optical network, and can ensure that the transmitted quantum signal is not damaged by the classical optical signal.
However, the security of the continuous variable quantum key distribution technology is greatly challenged by a strategy called interception-retransmission attack; this clearly limits the key generation rate and the distance of secure transmission of the QKD system.
Disclosure of Invention
One of the purposes of the invention is to provide a continuous variable quantum key distribution system based on differential phase shift, which can send modulated quantum signals to a quantum key receiving end through an optical fiber channel by a quantum key sending end; the quantum key receiving end randomly selects the received quantum signals, extracts local oscillator light for clock synchronization, simultaneously adopts two delay interferometers to receive signals for balanced homodyne detection, detects the signals and processes the signals; and data can be transmitted safely and efficiently.
The invention also aims to provide a method of the continuous variable quantum key distribution system based on the differential phase shift.
The invention provides a continuous variable quantum key distribution system based on differential phase shift, which comprises a quantum key sending end, an optical fiber channel and a quantum key receiving end; the quantum key sending end is connected with the optical fiber channel, and the optical fiber channel is connected with the quantum key receiving end; the quantum key sending end generates pulse laser, performs random phase modulation on the pulse laser, and performs signal attenuation simultaneously to obtain a modulated quantum signal; the optical fiber channel transmits the quantum signal modulated by the quantum key transmitting end to the quantum key receiving end; the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on the received quantum signals, extracts local oscillator light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing on output signals.
The quantum key sending end comprises a continuous pulse laser, a first electro-optic intensity modulator, a second electro-optic intensity modulator, a first electro-optic phase modulator, a first beam splitter, a second electro-optic phase modulator, a first adjustable attenuator, a second adjustable attenuator, a first extension line and a polarization coupler; a continuous pulse laser, a first electro-opticThe intensity modulator, the second electro-optic intensity modulator, the first electro-optic phase modulator, the first beam splitter, the second electro-optic phase modulator, the first adjustable attenuator and the polarization coupler are sequentially connected in series; the second output end of the first beam splitter is connected with the input end of the second adjustable attenuator, and the output end of the second adjustable attenuator is connected with the second input end of the polarization coupler through a first extension line; the output end of the polarization coupler is the output end of the quantum key sending end; the continuous pulse laser is used for generating pulse laser and sending the pulse laser to the first electro-optical intensity modulator; the first electro-optical intensity modulator is used for carrying out pulse modulation on coherent light generated by the continuous pulse laser and outputting a pulse coherent light signal with rated frequency; the second electro-optical intensity modulator is used for carrying out amplitude modulation on the coherent laser output by the first electro-optical intensity modulator so that the modulated optical signal meets Rayleigh distribution; the first electro-optical phase modulator is used for carrying out phase modulation on the optical signals output by the second electro-optical intensity modulator, so that the modulated optical signals meet the requirement of uniform distribution, and simultaneously, after the modulation of the second electro-optical intensity modulator and the first electro-optical phase modulator, the signal light is in a Gaussian coherent state; the first beam splitter is used for splitting the pulse laser passing through the first electro-optic phase modulator into two beams, wherein 10% of the two beams are signal light and are issued to the second electro-optic phase modulator, and 90% of the two beams are local oscillator light and are issued to the second adjustable attenuator; a second electro-optical phase modulator for performing the signal light separated by the first beam splitter
And
the random phase of the optical field is modulated and sent to a first adjustable attenuator, after the random phase of the optical field is modulated by a second electro-optic phase modulator, an orthogonal component X of the optical field is unchanged, an orthogonal component P obeys Gaussian distribution, the orthogonal component X refers to the amplitude of light, and the orthogonal component P refers to the phase of the light; the first adjustable attenuator attenuates the received signal light energy to the quantum level, becomes coherent light and sends the coherent light to the polarization coupler; the second adjustable attenuator is used for receivingThe light energy of the local oscillator is attenuated to the quantum level, becomes weak coherent light and is sent to the polarization coupler through the first extension line; the first extension line adopts a polarization-maintaining optical fiber for time multiplexing, and any polarization and phase drift possibly occurring between the signal light and the local oscillator light in the transmission process are avoided; and the polarization coupler is used for coupling the signal light of the quantum level and the local oscillator light separated by the first beam splitter to an optical fiber and transmitting the signal light and the local oscillator light to a receiving end through a quantum channel.
The quantum key receiving end comprises a third electro-optic phase modulator, a polarization beam splitter, a second extension line, a second beam splitter, a third beam splitter, a fourth beam splitter, a first delay interferometer, a second delay interferometer, a first homodyne detector, a second homodyne detector and a detection module; the third electro-optic phase modulator receives the quantum signal sent by the optical fiber channel and sends the quantum signal to the polarization beam splitter; the first output end of the polarization beam splitter sends the signal to the third beam splitter through a second extension line, and the second output end of the polarization beam splitter sends the signal to the second beam splitter; the third beam splitter sends the signals to the first delay interferometer and the second delay interferometer respectively; the second beam splitter sends the signals to the fourth beam splitter and the detection module respectively; the first delay interferometer and the fourth beam splitter send signals into a second homodyne detector; the second delay interferometer and the fourth beam splitter send signals into the first homodyne detector; the third electro-optical phase modulator is used for selecting and measuring the orthogonal component X and the orthogonal component P and carrying out phase modulation on the received quantum signals; the polarization beam splitter is used for splitting the received quantum signals into two beams of light, wherein 10% of the beams of light are signal light and are transmitted to the third beam splitter through a second extension line, and 90% of the beams of light are local oscillator light and are transmitted to the second beam splitter; the second extension line adopts a polarization-maintaining optical fiber, so that any polarization and phase drift possibly occurring between the signal light and the local oscillator light in the transmission process are avoided; the second beam splitter is used for splitting the received local oscillation light into two beams of sub local oscillation light with the same frequency, the same phase and the same polarization direction, wherein one beam of sub local oscillation light is sent to the fourth beam splitter, and the other beam of sub local oscillation light is sent to the detection module; the third beam splitter is used for splitting the received signal light into two beams of sub-signal light with the same frequency, the same phase and the same polarization direction, one beam of sub-signal light is sent to the first homodyne detector through the second delay interferometer with the phase difference of 0, and the other beam of sub-signal light is sent to the second homodyne detector through the first delay interferometer with the phase difference of pi; the fourth beam splitter is used for splitting the received sub local oscillator light into two beams of sun local oscillator light with same frequency and phase and same polarization direction, wherein one beam of sun local oscillator light is sent to the first homodyne detector, and the other beam of sun local oscillator light is sent to the second homodyne detector; the second delay interferometer generates delay interference with a phase difference of 0; the first delay interferometer generates delay interference with a phase difference of pi; the first homodyne detector is used for performing homodyne detection on the sun local oscillator light uploaded by the fourth beam splitter and the optical signal uploaded by the first delay interferometer and sending a detection result to the detection module; the second homodyne detector is used for performing homodyne detection on the sun local oscillator light uploaded by the fourth beam splitter and the optical signal uploaded by the first delay interferometer; and the sub local oscillator light output by the second beam splitter, the detection result output by the first homodyne detector and the detection result output by the second homodyne detector are uploaded to the detection module for post-processing.
The first electro-optic phase modulator, the second electro-optic phase modulator and the third electro-optic phase modulator are all MPZ-LN-10 in model number.
The first adjustable attenuator and the second adjustable attenuator are both of the type LBB 001590.
The model of the polarization coupler is MCHPBS/C-1550.
The second beam splitter, the third beam splitter and the fourth beam splitter are all beam splitters with the model number of BSW04, and the splitting ratio is 50: 50.
the models of the first delay interferometer and the second delay interferometer are both MINT and WT-MINT; the first homodyne detector and the second homodyne detector both adopt a balanced detector BPD-002.
The first extension line and the second extension line are both 80m extension lines.
The invention also provides a method of the continuous variable quantum key distribution system based on the differential phase shift, which is characterized by comprising the following steps:
s1: the quantum key sending end generates pulse laser, performs random phase modulation on the pulse laser, and performs signal attenuation simultaneously to obtain a modulated quantum signal;
s2: the optical fiber channel transmits the modulated quantum signals to a quantum key receiving end;
s3: the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on the received quantum signals, extracts local oscillator light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing on output signals.
The continuous variable quantum key distribution system and method based on differential phase shift, provided by the invention, apply the differential phase shift method for distributing the discrete quantum variable quantum key to the distribution of the continuous variable quantum key, so that the quantum key is high in reliability, good in performance, low in cost and convenient to implement in the distribution process.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention.
FIG. 2 is a schematic flow chart of the method of the present invention.
Detailed Description
FIG. 1 is a schematic structural diagram of the system of the present invention: the invention provides a continuous variable quantum key distribution system based on differential phase shift, which comprises a quantum key sending end, an optical fiber channel and a quantum key receiving end; the quantum key sending end is connected with the optical fiber channel, and the optical fiber channel is connected with the quantum key receiving end; the quantum key sending end generates pulse laser, performs random phase modulation on the pulse laser, and performs signal attenuation simultaneously to obtain a modulated quantum signal; the optical fiber channel transmits the quantum signal modulated by the quantum key transmitting end to the quantum key receiving end; the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on the received quantum signals, extracts local oscillator light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing on output signals.
In specific implementation, the quantum key sending end comprises a continuous pulse laser and a second pulse laserThe device comprises an electro-optical intensity modulator, a second electro-optical intensity modulator, a first electro-optical phase modulator, a first beam splitter, a second electro-optical phase modulator, a first adjustable attenuator, a second adjustable attenuator, a first extension line and a polarization coupler; the continuous pulse laser, the first electro-optic intensity modulator, the second electro-optic intensity modulator, the first electro-optic phase modulator, the first beam splitter, the second electro-optic phase modulator, the first adjustable attenuator and the polarization coupler are sequentially connected in series; the second output end of the first beam splitter is connected with the input end of the second adjustable attenuator, and the output end of the second adjustable attenuator is connected with the second input end of the polarization coupler through a first extension line; the output end of the polarization coupler is the output end of the quantum key sending end; the continuous pulse laser is used for generating pulse laser and sending the pulse laser to the first electro-optical intensity modulator; the first electro-optical intensity modulator is used for carrying out pulse modulation on coherent light generated by the continuous pulse laser and outputting a pulse coherent light signal with rated frequency; the second electro-optical intensity modulator is used for carrying out amplitude modulation on the coherent laser output by the first electro-optical intensity modulator so that the modulated optical signal meets Rayleigh distribution; the first electro-optical phase modulator is used for carrying out phase modulation on the optical signals output by the second electro-optical intensity modulator, so that the modulated optical signals meet the requirement of uniform distribution, and simultaneously, after the modulation of the second electro-optical intensity modulator and the first electro-optical phase modulator, the signal light is in a Gaussian coherent state; the first beam splitter is used for splitting the pulse laser passing through the first electro-optic phase modulator into two beams, wherein 10% of the two beams are signal light and are issued to the second electro-optic phase modulator, and 90% of the two beams are local oscillator light and are issued to the second adjustable attenuator; a second electro-optical phase modulator for performing the signal light separated by the first beam splitter
And
and then sent to the first adjustable attenuator, modulated by the second electro-optic phase modulator, the orthogonal component X of the light field is unchanged,the orthogonal component P follows Gaussian distribution, the orthogonal component X refers to the amplitude of light, and the orthogonal component P refers to the phase of the light; the first adjustable attenuator attenuates the received signal light energy to the quantum level, becomes coherent light and sends the coherent light to the polarization coupler; the second adjustable attenuator is used for attenuating the received local oscillator light energy to the quantum level, changing the local oscillator light energy into weak coherent light and sending the weak coherent light to the polarization coupler through the first extension line; the first extension line adopts a polarization-maintaining optical fiber for time multiplexing, and any polarization and phase drift possibly occurring between the signal light and the local oscillator light in the transmission process are avoided; and the polarization coupler is used for coupling the signal light of the quantum level and the local oscillator light separated by the first beam splitter to an optical fiber and transmitting the signal light and the local oscillator light to a receiving end through a quantum channel.
The quantum key receiving end comprises a third electro-optic phase modulator, a polarization beam splitter, a second extension line, a second beam splitter, a third beam splitter, a fourth beam splitter, a first delay interferometer, a second delay interferometer, a first homodyne detector, a second homodyne detector and a detection module; the third electro-optic phase modulator receives the quantum signal sent by the optical fiber channel and sends the quantum signal to the polarization beam splitter; the first output end of the polarization beam splitter sends the signal to the third beam splitter through a second extension line, and the second output end of the polarization beam splitter sends the signal to the second beam splitter; the third beam splitter sends the signals to the first delay interferometer and the second delay interferometer respectively; the second beam splitter sends the signals to the fourth beam splitter and the detection module respectively; the first delay interferometer and the fourth beam splitter send signals into a second homodyne detector; the second delay interferometer and the fourth beam splitter send signals into the first homodyne detector; the third electro-optical phase modulator is used for selecting and measuring the orthogonal component X and the orthogonal component P and carrying out phase modulation on the received quantum signals; the polarization beam splitter is used for splitting the received quantum signals into two beams of light, wherein 10% of the beams of light are signal light and are transmitted to the third beam splitter through a second extension line, and 90% of the beams of light are local oscillator light and are transmitted to the second beam splitter; the second extension line adopts a polarization-maintaining optical fiber, so that any polarization and phase drift possibly occurring between the signal light and the local oscillator light in the transmission process are avoided; the second beam splitter is used for splitting the received local oscillator light into two beams of sub local oscillator light with the same frequency, the same phase and the same polarization direction, one beam of sub local oscillator light is sent to the fourth beam splitter, the other beam of sub local oscillator light is sent to the detection module, and the sub local oscillator light sent to the detection module is used for clock synchronization, so that the orthogonal component of the optical field can be accurately measured only by using the same clock at the sending end and the receiving end; the third beam splitter is used for splitting the received signal light into two beams of sub-signal light with the same frequency, the same phase and the same polarization direction, one beam of sub-signal light is sent to the first homodyne detector through the second delay interferometer with the phase difference of 0, and the other beam of sub-signal light is sent to the second homodyne detector through the first delay interferometer with the phase difference of pi; the fourth beam splitter is used for splitting the received sub local oscillator light into two beams of sun local oscillator light with same frequency and phase and same polarization direction, wherein one beam of sun local oscillator light is sent to the first homodyne detector, and the other beam of sun local oscillator light is sent to the second homodyne detector; the second delay interferometer generates delay interference with a phase difference of 0; the first delay interferometer generates delay interference with a phase difference of pi; the first homodyne detector is used for performing homodyne detection on the sun local oscillator light uploaded by the fourth beam splitter and the optical signal uploaded by the first delay interferometer and sending a detection result to the detection module; the second homodyne detector is used for performing homodyne detection on the sun local oscillator light uploaded by the fourth beam splitter and the optical signal uploaded by the first delay interferometer; and the sub local oscillator light output by the second beam splitter, the detection result output by the first homodyne detector and the detection result output by the second homodyne detector are uploaded to the detection module for post-processing.
In specific implementation, the preferred models of each device are: the first electro-optic phase modulator, the second electro-optic phase modulator and the third electro-optic phase modulator are all MPZ-LN-10 in model number. The first adjustable attenuator and the second adjustable attenuator are both of the type LBB001590, the working wavelength is 15500nm, the attenuation range is 0.5dB to 60dB, and the optical signal can be attenuated to about 10 pulses by adjusting the input power8One photon. The model of the polarization coupler is MCHPBS/C-1550. The second beam splitter, the third beam splitter and the fourth beam splitter are all beam splitters with the model number of BSW04, and the splitting ratios are all 50: 50. the models of the first delay interferometer and the second delay interferometer are both MINT and WT-MINT; the first homodyne detector and the second homodyne detector both adopt a balanced detector BPD-002, the wavelength range is 1060nm-1560nm, the common mode rejection ratio is larger than 25dB, and the highest bandwidth is 200 MHz. The first extension line and the second extension line are both 80m extension lines.
FIG. 2 is a schematic flow chart of the method of the present invention; in the specific implementation process, the continuous variable quantum key distribution method based on differential phase shift comprises the following steps:
s1: the quantum key sending end generates pulse laser, performs random phase modulation on the pulse laser, and performs signal attenuation simultaneously to obtain a modulated quantum signal;
in specific implementation, the optical signal modulated by the second electro-optical intensity modulator and the first electro-optical phase modulator is in a Gaussian coherent state | X + jP>That is, the orthogonal component X and the orthogonal component P of the optical field of the signal light follow a gaussian distribution, where X ═ Acos θ and P ═ Asin θ, a and θ respectively represent the amplitude and phase of the signal, and the voltage ranges of the electrical signals are all [0V, 5V [](ii) a After Gaussian modulation, the signal light is divided into 10% of signal light and 90% of local oscillation light through a first beam splitter; subjecting the signal light split by the first beam splitter to
And
the tunable laser attenuator further attenuates the optical signal to become a weak coherent signal; carrying out signal attenuation on the local oscillation light separated by the first beam splitter, and then passing through an 80m delay line; the signal light passing through the tunable laser attenuator and the local oscillator light passing through the 80m delay line are coupled to an optical fiber through a polarization coupler;
s2: the optical fiber channel transmits the modulated quantum signals to a quantum key receiving end;
s3: the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on the received quantum signal, extracts local oscillator light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing on an output signal;
in specific implementation, the quantum key receiving end randomly selects and measures x or p regular components from the received quantum signals through the third electro-optic phase modulator; the signal light is separated into 10% of signal light and 90% of local oscillation light through a polarization beam splitter, the signal light separated through the polarization beam splitter is divided into two beams of signal light through a 80m delay line and a third beam splitter, and the two beams of signal light are respectively sent to a second delay interferometer with a phase difference of 0 and a first delay interferometer with a phase difference of pi; the local oscillator light after passing through the polarization beam splitter is divided into two local oscillator light beams with same frequency and phase and same polarization direction through a second beam splitter, and the splitting ratio is 50: 50, one beam of local oscillator light is sent to the fourth beam splitter, and the other beam of local oscillator light is sent to a computer terminal (PC) for clock synchronization; the local oscillator light separated by the second beam splitter is divided into two local oscillator lights with same frequency, same phase and same polarization direction by a fourth beam splitter, and the splitting ratio is 50: 50, one beam of local oscillator light is sent to a first homodyne detector, and the other beam of local oscillator light is sent to a second homodyne detector; and then carrying out balanced homodyne detection on the signal light received by the first delay interferometer and the second delay interferometer and the local oscillation light sent by the fourth beam splitter to obtain a result, wherein the phase difference of the first delay interferometer and the second delay interferometer is respectively 0 and pi/2, and the detected local oscillation light, the first homodyne detection signal and the second homodyne detection signal are sent to a detection module for processing.
The invention provides a continuous variable quantum key distribution technology based on differential phase shift, which utilizes an asymmetric Mach-Zehnder (M-Z) interferometer to interfere adjacent photon pairs in a continuous photon sequence, thereby extracting phase difference information between the adjacent photon pairs. Eve (attacker) measures the existence of continuous pulses, extracts a certain pulse sequence, stores and sends the pulse sequence to Bob (receiver); the intervention of Eve undoubtedly changes some phase difference information between the original adjacent photon pairs, which directly results in the increase of the bit error rate of the receiving end, and the possibility that Eve exposes itself is increased.
Furthermore, the method of the invention can change 1-cycle delay in the asymmetric MZ into 2-cycle delay or 3-cycle delay, thereby effectively increasing the influence of interception and retransmission attack on the error code of the QKD system and enabling the attack of an attacker to be easier to discover. The invention is suitable for optical fiber transmission, has the advantages of anti-interference and long limit transmission distance, has high generation rate of the key, and is very suitable for being applied to a new generation of QKD system.
Claims (8)
1. A continuous variable quantum key distribution system based on differential phase shift is characterized by comprising a quantum key sending end, an optical fiber channel and a quantum key receiving end; the quantum key sending end is connected with the optical fiber channel, and the optical fiber channel is connected with the quantum key receiving end; the quantum key sending end generates pulse laser, performs random phase modulation on the pulse laser, and performs signal attenuation simultaneously to obtain a modulated quantum signal; the optical fiber channel transmits the quantum signal modulated by the quantum key transmitting end to the quantum key receiving end; the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on the received quantum signal, extracts local oscillator light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing on an output signal;
the quantum key sending end comprises a continuous pulse laser, a first electro-optic intensity modulator, a second electro-optic intensity modulator, a first electro-optic phase modulator, a first beam splitter, a second electro-optic phase modulator, a first adjustable attenuator, a second adjustable attenuator, a first extension line and a polarization coupler; the continuous pulse laser, the first electro-optic intensity modulator, the second electro-optic intensity modulator, the first electro-optic phase modulator, the first beam splitter, the second electro-optic phase modulator, the first adjustable attenuator and the polarization coupler are sequentially connected in series; the second output end of the first beam splitter is connected with the input end of the second adjustable attenuator, and the output end of the second adjustable attenuator is connected with the second input end of the polarization coupler through a first extension line; the output end of the polarization coupler is the output end of the quantum key sending end; the continuous pulse laser is used for generating pulse laser and sending the pulse laser to the first electro-optical intensity modulator; a first electro-optical intensity modulator for applying a continuous pulse laserThe coherent light generated by the device is subjected to pulse modulation, and a pulse coherent light signal with a rated frequency is output; the second electro-optical intensity modulator is used for carrying out amplitude modulation on the coherent laser output by the first electro-optical intensity modulator so that the modulated optical signal meets Rayleigh distribution; the first electro-optical phase modulator is used for carrying out phase modulation on the optical signals output by the second electro-optical intensity modulator, so that the modulated optical signals meet the requirement of uniform distribution, and simultaneously, after the modulation of the second electro-optical intensity modulator and the first electro-optical phase modulator, the signal light is in a Gaussian coherent state; the first beam splitter is used for splitting the pulse laser passing through the first electro-optic phase modulator into two beams, wherein 10% of the two beams are signal light and are issued to the second electro-optic phase modulator, and 90% of the two beams are local oscillator light and are issued to the second adjustable attenuator; a second electro-optical phase modulator for performing the signal light separated by the first beam splitter
And
the random phase of the optical field is modulated and sent to a first adjustable attenuator, after the random phase of the optical field is modulated by a second electro-optic phase modulator, an orthogonal component X of the optical field is unchanged, an orthogonal component P obeys Gaussian distribution, the orthogonal component X refers to the amplitude of light, and the orthogonal component P refers to the phase of the light; the first adjustable attenuator attenuates the received signal light energy to the quantum level, becomes coherent light and sends the coherent light to the polarization coupler; the second adjustable attenuator is used for attenuating the received local oscillator light energy to the quantum level, changing the local oscillator light energy into weak coherent light and sending the weak coherent light to the polarization coupler through the first extension line; the first extension line adopts a polarization-maintaining optical fiber for time multiplexing, and any polarization and phase drift possibly occurring between the signal light and the local oscillator light in the transmission process are avoided; the polarization coupler is used for coupling the signal light of the quantum level and the local oscillator light separated by the first beam splitter to an optical fiber and transmitting the signal light and the local oscillator light to a receiving end through a quantum channel;
the quantum key receiving end comprises a third electro-optic phase modulator, a polarization beam splitter and a second extensionThe system comprises a line, a second beam splitter, a third beam splitter, a fourth beam splitter, a first delay interferometer, a second delay interferometer, a first homodyne detector, a second homodyne detector and a detection module; the third electro-optic phase modulator receives the quantum signal sent by the optical fiber channel and sends the quantum signal to the polarization beam splitter; the first output end of the polarization beam splitter sends the signal to the third beam splitter through a second extension line, and the second output end of the polarization beam splitter sends the signal to the second beam splitter; the third beam splitter sends the signals to the first delay interferometer and the second delay interferometer respectively; the second beam splitter sends the signals to the fourth beam splitter and the detection module respectively; the first delay interferometer and the fourth beam splitter send signals into a second homodyne detector; the second delay interferometer and the fourth beam splitter send signals into the first homodyne detector; the third electro-optical phase modulator is used for selecting and measuring the orthogonal component X and the orthogonal component P and carrying out phase modulation on the received quantum signals; the polarization beam splitter is used for splitting the received quantum signals into two beams of light, wherein 10% of the beams of light are signal light and are transmitted to the third beam splitter through a second extension line, and 90% of the beams of light are local oscillator light and are transmitted to the second beam splitter; the second extension line adopts a polarization-maintaining optical fiber, so that any polarization and phase drift possibly occurring between the signal light and the local oscillator light in the transmission process are avoided; the second beam splitter is used for splitting the received local oscillation light into two beams of sub local oscillation light with the same frequency, the same phase and the same polarization direction, wherein one beam of sub local oscillation light is sent to the fourth beam splitter, and the other beam of sub local oscillation light is sent to the detection module; a third beam splitter for splitting the received signal light into two sub-signal lights with same frequency, same phase and same polarization direction, one sub-signal light being sent to the first homodyne detector via the second delay interferometer with a phase difference of 0, the other sub-signal light being sent to the first homodyne detector via a phase difference of 0
The first delay interferometer of (a) is sent to a second homodyne detector; a fourth beam splitter for splitting the received sub local oscillator light into two beams of sun local oscillator light with same frequency and phase and same polarization direction, one beam of sun local oscillator light being sent to the first homodyne detector, and another beam splitter for splitting the received sub local oscillator light into two beams of sun local oscillator light with same frequency and phase and same polarization directionSending the one beam of sun local oscillator light to a second homodyne detector; the second delay interferometer generates delay interference with a phase difference of 0; the first delay interferometer generates a phase difference of
The delayed interference of (2); the first homodyne detector is used for performing homodyne detection on the sun local oscillator light uploaded by the fourth beam splitter and the optical signal uploaded by the first delay interferometer and sending a detection result to the detection module; the second homodyne detector is used for performing homodyne detection on the sun local oscillator light uploaded by the fourth beam splitter and the optical signal uploaded by the first delay interferometer; sub local oscillator light output by the second beam splitter, a detection result output by the first homodyne detector and a detection result output by the second homodyne detector are uploaded to a detection module for post-processing;
interfering adjacent photon pairs in the continuous photon sequence by using an interferometer so as to extract phase difference information between the adjacent photon pairs; the 1-cycle delay in the interferometer is changed into 2 cycles or 3 cycles, so that the influence of interception and retransmission attack on the QKD system error code is effectively increased, and the attack of an attacker is easier to discover.
2. The differential phase shift-based continuous variable quantum key distribution system of claim 1, wherein the first electro-optic phase modulator, the second electro-optic phase modulator, and the third electro-optic phase modulator are each model numbers MPZ-LN-10.
3. The differential phase shift-based continuous variable quantum key distribution system according to claim 2, wherein the first adjustable attenuator and the second adjustable attenuator are each of LBB001590 type.
4. The differential phase shift-based continuously variable quantum key distribution system of claim 3, wherein the polarization coupler is model MCHPBS/C-1550.
5. The continuous variable quantum key distribution system based on differential phase shift according to claim 4, wherein the second beam splitter, the third beam splitter and the fourth beam splitter are BSW04 beam splitters, and the splitting ratio is 50: 50.
6. the differential phase shift-based continuously variable quantum key distribution system of claim 5, wherein the first delay interferometer and the second delay interferometer are both types MINT and WT-MINT; the first homodyne detector and the second homodyne detector both adopt a balanced detector BPD-002.
7. The differential phase shift-based continuously variable quantum key distribution system of claim 6, wherein the first extension line and the second extension line are 80m extension lines.
8. A method for applying the continuous variable quantum key distribution system based on differential phase shift according to any claim 1 to 7, characterized by comprising the following steps:
s1: the quantum key sending end generates pulse laser, performs random phase modulation on the pulse laser, and performs signal attenuation simultaneously to obtain a modulated quantum signal;
s2: the optical fiber channel transmits the modulated quantum signals to a quantum key receiving end;
s3: the quantum key receiving end carries out random selection of an orthogonal component X and an orthogonal component P on the received quantum signals, extracts local oscillator light for clock synchronization, then carries out balanced homodyne detection to obtain a result, and carries out post-processing on output signals.
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