CN108712254B - Quantum key distribution system and method - Google Patents
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- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
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Abstract
The invention provides a quantum key distribution system and a quantum key distribution method. The system comprises the following components: a transmitting device and a receiving device; transmitting device to receiving deviceRandom transmission of two pre-promised non-orthogonal quantum states
And | φ >; discarding the measurement result as empty,
Or | φ > the corresponding data; the receiving device randomly uses one of the two groups of measuring bases to measure the received quantum state to obtain a measuring result; the measured result is not empty,
Information of the data position of sum phi is sent to the sending device, and the measurement result is discarded,
Or | φ > the corresponding data; the sending device and the receiving device carry out parameter estimation according to the reserved data of the preset part to obtain an error rate; and when the error rate is not greater than the preset threshold value, correcting the error and carrying out privacy amplification to obtain a secret key. The invention can distribute the quantum key safely only by using two non-orthogonal quantum states, thereby reducing the equipment cost and improving the key rate.
Description
Technical Field
The present application relates to the field of quantum information technology, and in particular, to a quantum key distribution system and method.
Background
With the vigorous development of internet technology, the importance of communication security is increasing day by day. In many cases, both parties of the communication desire to communicate securely using a common channel. For example, when a user submits an account number and a password to internet banking, the user wants the information to be confidential during the transmission process, i.e., the information cannot be intercepted by any third party. A currently widely used encryption method is a public key encryption algorithm. Such algorithms are based on the algorithm complexity of some mathematical problems, and as science and technology develops, their security is threatened. Therefore, there is a need to develop a more secure and reliable encryption method.
The quantum key distribution technology is a brand new key distribution scheme based on quantum mechanical characteristics, and is one of the technologies with the most application prospects in the quantum information technology. The technology borrows a public channel to ensure that a safe random secret key is shared between two communication parties. And in combination with a one-time pad encryption method, the shared random key can be used for encrypting information in communication, so that the communication safety is ensured. The security of quantum key distribution is based on physics rationale and is therefore information-theoretic secure.
Currently, some commercial quantum key distribution systems are already provided in the prior art, and the systems are mostly based on the BB84 protocol. The system is divided into a transmitting device and a receiving device. In the BB84 protocol, the quantum signal source used for transmitting the key is a single photon, and the key information to be transmitted is encoded in the polarization state (or polarization direction) of the single photon. The transmitting device encodes information in four different quantum states |0>, |1>, | + >, and | - >. On the hardware level, the four quantum states can be encoded by different degrees of freedom of photons. For example, when polarization encoding is used, single photons linearly polarized along the horizontal direction, the vertical direction, 45 ° and 135 ° can be selected as carriers of quantum information, and the single photons in the polarization states of the four directions can be represented by four quantum states of |0>, |1>, | + >, and | - >; similarly, when phase encoding is used, four phase values between two coherent wave packets of photons can be used to represent the four quantum states |0>, |1>, | + >, and | - >.
Wherein, in the above four quantum states, |0> and |1> are orthogonal to each other, so that a group of measurement bases can be formed, which are called as straight measurement bases (abbreviated as Z base, the same below), and |0> state and |1> state are two eigenstates of the Z base; since | + > and | - > are also orthogonal to each other, another set of measurement bases can be formed, which are called oblique measurement bases (X base for short, the same applies hereinafter), and the | + > state and the | - > state are two eigenstates of the X base.
The relationship between the four quantum states described above is as follows:
in order to transmit classical information, the BB84 protocol prepares one photon on the above four quantum states and contracts the encoded information represented by each quantum state. For example, in the BB84 protocol, photons are encoded by polarization of light, and are randomly encoded on the Z basis and the X basis with equal probability. A sender randomly generates a string consisting of 0 and 1 bits, and when the coding is selected under the Z base, the sender codes 0 into |0> and 1 into |1>; when the encoding is selected under the X base, the sender encodes 0 into | + >, and encodes 1 into | - >. Then, the sender sends the quantum state to the receiver through a quantum channel, and the receiver uses an X basis or a Z basis to measure the quantum state sent from the sender with equal probability; then, the sender and the receiver publish the measurement bases selected for use in encoding or measuring respectively in the authenticated classical channel, and thereby screen out encoded data when both select the same measurement base for encoding or measuring as the transmitted key information.
Therefore, in executing the BB84 protocol, the transmitting device needs to randomly transmit the four quantum states. For this reason, there are generally two methods for hardware implementation: one is to adopt a laser and rapidly modulate the emitted light (with the freedom degrees of polarization, phase and the like); the other is to use four lasers (as shown in fig. 1), each of which fixedly transmits a quantum state, and an optical switch is used to multiplex four paths of light onto one channel.
An important performance parameter of a practical key distribution system is the transmission rate of the sending device. In general, the higher the transmission rate, the higher the system final key rate. However, the quantum key distribution system in the prior art requires four quantum states to be randomly transmitted. As shown above, if the transmitting apparatus uses a laser, the system has a high requirement on the modulation rate of the modulation component; if a multiple laser scheme is used, the system has higher requirements on the number of lasers and the speed of the optical switch. Therefore, it can be seen that, in the two methods in the prior art, since four quantum states are used, the cost of the transmitting end is high, and the final key rate of the system is low.
Disclosure of Invention
In view of this, the present invention provides a quantum key distribution system and method, so that only two non-orthogonal quantum states are needed to perform secure quantum key distribution, thereby reducing the device cost and increasing the key rate.
The technical scheme of the invention is realized as follows:
a quantum key distribution system, the system comprising: a transmitting device and a receiving device;
the transmitting device and the receiving device are connected through a transmission channel;
the transmitting device is used for randomly transmitting two pre-agreed non-orthogonal quantum states to the receiving device
And | phi>(ii) a And also for discarding measurement results as empty based on the information sent for each quantum state and received data location,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; when the error rate is not greater than a preset threshold value, carrying out error correction and privacy amplification to obtain a secret key;
wherein, the
And | phi>Two non-orthogonal quantum states are randomly selected from four quantum states belonging to two groups of different measurement bases, and the two selected quantum states are coded in advance;
the receiving device is used for measuring the received quantum state by using one of the two groups of measuring bases at random to obtain a measuring result; and also for measuring whether the measurement result is empty,
And | phi>The information of the data position of (2) is transmitted to the transmitting device, and the measurement result is discarded asEmpty,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; and when the error rate is not greater than the preset threshold value, correcting the error and carrying out privacy amplification to obtain a secret key.
Preferably, the transmission channel is an optical fiber or a free space.
Preferably, the sending device includes: a first controller, a laser and a modulator;
the receiving apparatus includes: the single photon detection unit and the second controller;
the signal output end of the first controller is connected with the laser and the modulator;
the output end of the laser is connected with the modulator;
the output end of the modulator is connected with the single photon detection unit through a transmission channel;
the output end of the single photon detection unit is connected with the second controller;
and the synchronous signal end of the first controller is connected with the synchronous signal end of the second controller.
Preferably, the transmitting device includes: the laser system comprises a first controller, a first laser, a second laser and a modulator;
the receiving apparatus includes: the single photon detection unit and the second controller;
the signal output end of the first controller is respectively connected with the first laser, the second laser and the modulator;
the output ends of the first laser and the second laser are connected with the modulator;
the output end of the modulator is connected with the single photon detection unit through a transmission channel;
the output end of the single photon detection unit is connected with a second controller;
and the synchronous signal end of the first controller is connected with the synchronous signal end of the second controller.
Preferably, the modulator is an optical switch or an optoelectronic modulator.
Preferably, the single photon detection unit includes: a measurement basis selector and a single photon detector;
the measurement base selector is arranged in front of the single-photon detector;
the measuring base selector is used for randomly selecting a group of measuring bases from the two groups of measuring bases;
and the single photon detector is used for measuring the received quantum state according to the selected measurement basis to obtain a measurement result and sending the measurement result to the second controller.
Preferably, the measurement base selector is an optical switch, an optoelectronic modulator or a beam splitter.
The invention also provides a quantum key distribution method, which comprises the following steps:
arbitrarily selecting two non-orthogonal quantum states from four quantum states belonging to two different measurement groups
And | phi>And coding the two selected quantum states in advance;
the transmitting device randomly transmits the two quantum states to the receiving device
And | phi>；
The receiving device randomly uses one of the two groups of measuring bases to measure the received quantum state to obtain a measuring result;
the receiving device will measure whether the result is empty,
And | phi>The information of the data position of (2) is sent to the sending device;
the transmitting device and the receiving device discard the measurement result as empty,
Or | phi>The corresponding data;
the sending device and the receiving device carry out parameter estimation according to the reserved data of the preset part to obtain an error rate; and when the error rate is not greater than the preset threshold value, the transmitting device and the receiving device carry out error correction and privacy amplification to obtain a secret key.
Preferably, the two different measurement bases are a direct measurement base and an oblique measurement base.
Preferably, the two quantum states
And | phi>The included angle therebetween is not 45 degrees or 135 degrees.
It can be seen from the above technical solutions that, in the quantum key distribution system and method of the present invention, since the sending device can transmit the key to the receiving device only using two non-orthogonal quantum states without using four quantum states, thereby completing the distribution of the quantum key, compared with the prior art, the technical solution of the present invention can perform the secure quantum key distribution on the premise of ensuring the security only using fewer quantum states, thereby effectively reducing the equipment cost and improving the key rate.
Drawings
Fig. 1 is a schematic structural diagram of a quantum key distribution system in the prior art.
Fig. 2 is a schematic diagram of an overall structure of a quantum key distribution system in the embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a quantum key distribution system in a first embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a quantum key distribution system in a second embodiment of the present invention.
Fig. 5 is a schematic flow chart of a quantum key distribution method in the embodiment of the present invention.
Detailed Description
In order to make the technical scheme and advantages of the invention more apparent, the invention is further described in detail with reference to the accompanying drawings and specific embodiments.
Fig. 2 is a schematic diagram of an overall structure of a quantum key distribution system in the embodiment of the present invention. As shown in fig. 2, the quantum key distribution system in the embodiment of the present invention includes: a transmitting device 21 and a receiving device 22;
the transmitting device 21 and the receiving device 22 are connected through a transmission channel 23;
the transmitting device 21 is used for randomly transmitting two pre-agreed non-orthogonal quantum states to the receiving device 22
And | phi>(ii) a And also for discarding measurement results as empty based on the information sent for each quantum state and received data location,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; when the error rate is not greater than a preset threshold value, carrying out error correction and carrying out privacy amplification to obtain a secret key;
wherein, the
And | phi>Two non-orthogonal quantum states are randomly selected from four quantum states belonging to two groups of different measurement bases, and the two selected quantum states are coded in advance;
the receiving device 22 is configured to measure the received quantum state by using one of the two measurement bases at random to obtain a measurement result; and also for measuring whether the measurement result is empty,
And | phi>Sends the information of the data position of (2) to the transmitting device 21, and discards the measurement result as empty,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; when the error rate is not greater than the preset threshold valueAnd correcting errors and amplifying privacy to obtain a secret key.
With the quantum key distribution system described above, the transmitter 21 can transmit a key to the receiver 22 using two quantum states, thereby completing the distribution of the quantum key.
In the technical scheme of the invention, quantum state
And | phi>In two non-orthogonal quantum states, i.e.
Therefore, can be provided with
The corresponding measurement basis is
And phi>The corresponding measurement basis is { | φ { | ]>，|φ⊥>And (c) the step of (c) in which,
therefore, in a preferred embodiment of the present invention, the two different sets of measurement bases can be the straight measurement base (Z base) and the oblique measurement base (X base) described above. Thus, any two non-orthogonal quantum states can be selected from the four quantum states |0>, |1>, | + >, and | - > of the Z and X groups.
For example, preferably, in embodiments of the present invention, two quantum states are selected
And | φ may be |0>、|+>The method can be as follows: i0>、|->The method can be as follows: l 1>、|+>It can also be: l 1>、|->。
In addition, preferably, in the embodiment of the present invention, the two selected quantum states can also be other two non-orthogonal quantum states
And | phi>And the two quantum states
And | phi>The included angle therebetween is not 45 degrees or 135 degrees (e.g., may be 20 degrees, 30 degrees, 40 degrees, etc.).
After the two quantum states are selected, the two selected quantum states can be encoded.
For example, preferably, in the embodiment of the present invention, when the two selected quantum states are: if |0>, + >, 0 can be encoded as |0> and 1 can be encoded as | + >. In addition, when the two selected quantum states are selected in other selection modes, the analogy can be performed, and therefore, the description is omitted.
The transmitting device may then randomly transmit the two quantum states to the receiving device
And | phi>And the receiving device can use the two sets of measurement bases randomly
And { | φ { |)>，|φ ⊥ >And } measuring the received quantum state by using a set of measurement bases to obtain a measurement result.
When the receiving device uses the measuring base
When measuring the received quantum state, if the received quantum state is
The measurement result must be
And if the received quantum state is | φ>Then the measurement result may be
Or may be
When the receiving device uses the measurement basis { | φ { [ phi ]>，|φ ⊥ >When measuring the received quantum state, if the received quantum state is | φ }>Then the measurement result must be | φ>(ii) a And if the received quantum state is
The measurement result may be | phi |>And may also be | φ ⊥ >。
It can therefore be seen that if the measurement result is
And the received quantum state may be
May also be phi>(ii) a If the measurement result is
The received quantum state must be | phi |>. Similarly, if the measurement result is | φ |>Nor can it be determined that the received quantum state is
Is also phi>(ii) a And if the measurement result is | phi ⊥ >Then the received quantum state must be
In addition, in some cases (for example, the quantum state is not transmitted successfully or transmitted incorrectly due to some problems occurring in the transmission process of the quantum state), the measurement result of the receiving device may also be Null (Null), that is, the corresponding data of the quantum state is not measured, and the measurement result is not the same
|φ>、
And | phi ⊥ >But is an empty result.
Therefore, the receiving device will measure whether the measurement result is empty,
And | phi>(i.e., the measurement result is
Or | phi ⊥ >) The data location information of (2) is transmitted to the transmitting device, but the information of the measurement basis used by the receiving device and the measurement result are not disclosed.
The transmitting apparatus and the receiving apparatus can discard the measurement result as empty, respectively,
Or | phi>Corresponding data, only the measurement result is left
And | phi ⊥ >Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; and when the error rate is not greater than a preset threshold value, carrying out error correction and privacy amplification to obtain a secret key.
Therefore, by using the quantum key distribution system, the distribution of the quantum key can be completed by using two quantum states.
In addition, preferably, in the embodiment of the present invention, the transmission channel 23 is an optical fiber or a free space.
In addition, in the technical solution of the present invention, the above-described transmission apparatus may be implemented in various ways. The following will describe the technical solution of the present invention by taking two specific implementation manners as examples.
In the first embodiment, only one laser is provided in the transmitting device.
For example, in an embodiment of the present invention, preferably, fig. 3 is a schematic structural diagram of a quantum key distribution system in a first embodiment of the present invention, and as shown in fig. 3, the sending device 21 includes: a first controller 211, a laser 212, and a modulator 213; the receiving device 22 includes: single photon detection unit 221 and second controller 222;
the signal output end of the first controller 211 is connected with the laser 212 and the modulator 213; the output end of the laser 212 is connected with a modulator 213; the output end of the modulator 213 is connected with the single photon detection unit 221 through a transmission channel 23; the output end of the single photon detection unit 221 is connected with the second controller 222; the synchronization signal terminal of the first controller 211 is connected to the synchronization signal terminal of the second controller 222.
In the technical scheme of the present invention, the first controller 211 may control the laser 212 to output a single photon by sending a control signal, and control the modulator 213 to randomly modulate the received single photon by sending a random control signal; and for discarding measurement results as null based on information of the respective quantum states sent by the modulator 213 and the received data location,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; when the error rate is not greater than a preset threshold value, carrying out error correction and carrying out privacy amplification to obtain a secret key;
the laser 212 is configured to output a single photon to the modulator 213 according to a control signal;
the modulator 213 is configured to randomly modulate the received single photon into two predetermined quantum states according to a random control signal
And | phi>And transmits the modulated quantum state to the single photon detection unit 221 through the transmission channel 23;
wherein, the
And | phi>Two non-orthogonal quantum states are randomly selected from four quantum states belonging to two groups of different measurement bases, and the two selected quantum states are coded in advance;
the single photon detection unit 221 randomly measures the received quantum state by using one of the two measurement bases to obtain a measurement result, and sends the measurement result to the second controller 222;
the second controller 222 is used for determining whether the measurement result is empty,
And | phi>Is sent to the first controller 211, and is further used to discard the measurement result as empty,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; and when the error rate is not greater than the preset threshold value, correcting the error and carrying out privacy amplification to obtain a secret key.
Through the quantum key distribution system, the sending device can transmit the key to the receiving device by using two quantum states, and the distribution of the quantum key is completed.
In a second embodiment, two lasers are provided in the transmitting device.
For example, in an embodiment of the present invention, preferably, fig. 4 is a schematic structural diagram of a quantum key distribution system in a second embodiment of the present invention, as shown in fig. 4, the sending device 21 includes: a first controller 41, a first laser 42, a second laser 43, and a modulator 44; the receiving device 21 includes: single photon detection unit 221 and second controller 222;
the signal output end of the first controller 41 is respectively connected with the first laser 42, the second laser 43 and the modulator 44; the output ends of the first laser 42 and the second laser 43 are both connected with a modulator 44; the output end of the modulator 44 is connected with the single photon detection unit 221 through a transmission channel 23; the output end of the single photon detection unit 221 is connected with the second controller 222; the synchronization signal terminal of the first controller 41 is connected to the synchronization signal terminal of the second controller 222.
In the technical solution of the present invention, the first controller 41 may control the first laser 42 or the second laser 43 to output a single photon with a determined quantum state by sending a control signal, and control the modulator 44 to randomly select one quantum state from the two received quantum states by sending a random control signal; and for discarding measurements as empty based on information of the various quantum states sent by modulator 44 and the received data location,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; when the error rate is not greater than a preset threshold value, carrying out error correction and privacy amplification to obtain a secret key;
the first laser 42 and the second laser 43 respectively output single photons having a determined first quantum state and a determined second quantum state to the modulator 44 according to a control signal; wherein the first quantum state and the second quantum state are two predetermined quantum states
And | phi>；
The above-mentioned
And | phi>Two non-orthogonal quantum states are randomly selected from four quantum states belonging to two groups of different measurement bases, and the two selected quantum states are coded in advance;
the modulator 44 is configured to randomly select one of the two received quantum states, and transmit the selected quantum state to the single photon detection unit 221 through the transmission channel 23;
the single photon detection unit 221 randomly uses one of the two measurement bases to measure the received quantum state, so as to obtain a measurement result, and sends the measurement result to the second controller 222;
the second controller 222 is used for determining whether the measurement result is empty,
And | phi>Is sent to the first controller 41, and is also used to discard the measurement result as empty,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; and when the error rate is not greater than the preset threshold value, carrying out error correction and privacy amplification to obtain a secret key.
In addition, preferably, in the embodiment of the present invention, the modulator 44 may be an optical switch. For example, in a particularly preferred embodiment of the present invention, when two lasers are used, an optical switch may be used as modulator 44.
For example, in an embodiment of the present invention, the modulator 44 may be an electro-optical modulator (EOM). For example, in a particularly preferred embodiment of the present invention, when only one laser is used, the EOM may be used as the modulator 44.
In addition, preferably, in an embodiment of the present invention, the single photon detection unit 221 may further include: a measurement basis selector and a single photon detector;
the measurement base selector is arranged in front of the single-photon detector;
the measuring base selector is used for randomly selecting a group of measuring bases from the two groups of measuring bases;
the single photon detector is configured to measure the received quantum state according to the selected measurement basis to obtain a measurement result, and send the measurement result to the second controller 222.
In addition, preferably, in the embodiment of the present invention, the measurement basis selector may be a modulator, for example, an optical switch or an electro-optical modulator (EOM). The modulator can randomly select one group of measuring bases from two groups of measuring bases by dynamically modulating photons (polarization).
Preferably, in an embodiment of the present invention, the measurement-based selector may also be a Beam Splitter (BS). The two outlets of the beam splitter can be respectively connected with an optical component (such as a polaroid) and then connected with a single photon detector. Thus, the beam splitter can use a passive approach to randomly select one of the two sets of measurement bases.
Through the quantum key distribution system, the sending device can transmit the key to the receiving device by using two quantum states, and the distribution of the quantum key is completed.
In addition, in the technical scheme of the invention, a quantum key distribution method is also provided.
Fig. 5 is a schematic flowchart of a quantum key distribution method in the embodiment of the present invention. As shown in fig. 5, the quantum key distribution method in the embodiment of the present invention includes:
For example, preferably, in embodiments of the present invention, two different sets of measurement bases may be selected. The two different sets of measurement bases may be the straight measurement base (Z base) and the oblique measurement base (X base) described above. Any two non-orthogonal quantum states can then be selected from the four quantum states |0>, |1>, | + >, and | - > of the Z and X bases.
For example, preferably, in embodiments of the present invention, two quantum states are selected
And | φ may be |0>、|+>The method can be as follows: |0>、|->It can be that: l 1>、|+>It can also be: l 1>、|->。
In addition, preferably, in the embodiment of the present invention, the two selected quantum states may be other two non-orthogonal quantum states
And | phi>And the two quantum states
And | phi>The included angle therebetween is not 45 degrees or 135 degrees (e.g., may be 20 degrees, 30 degrees, 40 degrees, etc.).
For convenience of description, the technical solution of the present invention will be clearly and specifically described below by taking one of the selected quantum states (i.e., the two selected quantum states: |0>, | + >) as an example.
After the two quantum states are selected, the two selected quantum states can be encoded.
For example, preferably, in the embodiment of the present invention, when the two selected quantum states are: if |0>, | + >, 0 can be encoded as |0> and 1 can be encoded as | + >.
The above are all two selected quantum states: the description of |0>, | + > is made for the example. When the two selected quantum states are other selection modes, the analogy can be carried out, and therefore, the description is omitted.
In the technical scheme of the invention, the two quantum states are selected
And | phi>Then, the transmitting end can use the two selected quantum states to transmit random information to the receiving device, i.e. the transmitting device transmits the random information to the receiving deviceRandomly transmitting the two quantum states
And | phi>。
And 53, the receiving device randomly uses one of the two measurement bases to measure the received quantum state to obtain a measurement result.
In the technical scheme of the invention, the device can be provided with
The corresponding measurement basis is
And phi>The corresponding measurement basis is { | φ { |)>，|φ ⊥ >-means for, among other things,
therefore, in this step, the receiving apparatus can be randomly used
And { | φ>，|φ ⊥ >And measuring the received quantum state by any group of measurement bases in the measurement device to obtain a measurement result.
For example, when the two groups of measurement bases are a direct measurement base and an oblique measurement base, respectively, the receiving device may randomly use the direct measurement base or the oblique measurement base to measure the received quantum state, and obtain corresponding measurement results.
In this step, the receiving device determines whether the measurement result is empty,
And | phi>(i.e., the measurement result is
Or | phi ⊥ >) The data position information of (2) is transmitted to the transmitting device, but the information of the measurement basis used by the receiving device and the measurement result are not disclosed.
For example, in the preferred embodiment of the present invention, when the two quantum states transmitted by the transmitting device are: if |0>, | + >, the receiving apparatus transmits information of the data position where the measurement result is |1> or | minus > to the transmitting apparatus in this step.
In the technical scheme of the invention, the measurement result is empty because the transmitting device and the receiving device are discarded,
Or | phi>Corresponding data, only the measurement result is left
Or | phi ⊥ >And the corresponding data, therefore, the sending device and the receiving device can carry out parameter estimation according to the reserved data of the preset part, thereby obtaining the corresponding error rate. In the present invention, the above-mentioned error rate can be obtained by using a common parameter estimation method, which is not described herein again.
After the error rate is obtained, whether the error rate is greater than a preset threshold value can be judged. If the error rate is greater than the preset threshold, it indicates too many errors, and the obtained key information must be discarded, so the whole process will be terminated. If the error rate is greater than the predetermined threshold, it is an error rate within an acceptable range, so that the following step 57 may be performed to obtain the final key.
In the technical solution of the present invention, a common error correction method may be used to correct errors in the received original key information, so as to obtain the corrected key information, and therefore, the specific error correction method is not described herein again.
In the technical scheme of the invention, the common privacy amplification method can be used for carrying out privacy amplification on the corrected key information so as to obtain the final key, and therefore, the specific privacy amplification method is not described in detail herein.
Through the above steps 51 to 58, the key can be transmitted between the transmitting apparatus and the receiving apparatus.
In summary, in the technical solution of the present invention, since the sending device can transmit the secret key to the receiving device only by using two non-orthogonal quantum states without using four quantum states, and complete the distribution of the quantum secret key, compared with the prior art, the technical solution of the present invention can perform the secure quantum secret key distribution on the premise of ensuring the security by using fewer quantum states, thereby effectively reducing the equipment cost and improving the secret key rate.
In addition, in the technical scheme of the invention, one laser can be used as the sending device, two lasers can also be used as the sending device, and the sending device can be selected according to the requirements of practical application scenes. In addition, the technical scheme of the invention can be realized by using various physical implementation modes of quantum states such as polarization coding, phase coding and the like, and details are not repeated.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. A quantum key distribution system, comprising: a transmitting device and a receiving device;
the transmitting device and the receiving device are connected through a transmission channel;
the transmitting device is used for randomly transmitting two pre-agreed non-orthogonal quantum states to the receiving device
And | phi>(ii) a And also for discarding measurement results as empty based on the information sent for each quantum state and received data location,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; when the error rate is not greater than a preset threshold value, carrying out error correction and carrying out privacy amplification to obtain a secret key;
wherein, the
And | phi>Two non-orthogonal quantum states arbitrarily selected from four quantum states belonging to two different measurement groups are selected, and the two selected quantum states are encoded in advance
And | phi>The included angle between the two is not 45 degrees or 135 degrees;
the receiving device is used for measuring the received quantum state by using one of the two different measurement bases at random to obtain a measurement result; and also for measuring whether the measurement result is empty,
And | phi>The information of the data position of (2) is transmitted to the transmitting device, and the measurement result is discarded as empty,
Or | phi>Performing parameter estimation on the corresponding data according to the reserved preset part of data to obtain an error rate; and when the error rate is not greater than the preset threshold value, correcting the error and carrying out privacy amplification to obtain a secret key.
2. The system of claim 1, wherein:
the transmission channel is an optical fiber or free space.
3. The system of claim 1,
the transmission apparatus includes: a first controller, a laser and a modulator;
the receiving apparatus includes: the single photon detection unit and the second controller;
the signal output end of the first controller is connected with the laser and the modulator;
the output end of the laser is connected with the modulator;
the output end of the modulator is connected with the single photon detection unit through a transmission channel;
the output end of the single photon detection unit is connected with a second controller;
and the synchronous signal end of the first controller is connected with the synchronous signal end of the second controller.
4. The system of claim 1,
the transmission apparatus includes: a first controller, a first laser, a second laser and a modulator;
the receiving apparatus includes: the single photon detection unit and the second controller;
the signal output end of the first controller is respectively connected with the first laser, the second laser and the modulator;
the output ends of the first laser and the second laser are connected with the modulator;
the output end of the modulator is connected with the single photon detection unit through a transmission channel;
the output end of the single photon detection unit is connected with a second controller;
and the synchronous signal end of the first controller is connected with the synchronous signal end of the second controller.
5. The system of claim 4, wherein:
the modulator is an optical switch or an optoelectronic modulator.
6. The system of claim 4 wherein said single photon detection unit comprises: a measurement basis selector and a single photon detector;
the measurement base selector is arranged in front of the single-photon detector;
the measuring base selector is used for randomly selecting a group of measuring bases from two groups of different measuring bases;
and the single-photon detector is used for measuring the received quantum state according to the selected measurement basis to obtain a measurement result and sending the measurement result to the second controller.
7. The system of claim 6, wherein:
the measuring base selector is an optical switch, a photoelectric modulator or a beam splitter.
8. A method for quantum key distribution, the method comprising:
arbitrarily selecting two non-orthogonal quantum states from four quantum states belonging to two different measurement groups
And | phi>And pre-encoding the two selected quantum states
And | phi>The included angle between the two is not 45 degrees or 135 degrees;
the transmitting device randomly transmits the two quantum states to the receiving device
And | phi>；
The receiving device randomly uses one of the two different measurement bases to measure the received quantum state to obtain a measurement result;
the receiving device will measure whether the result is empty,
And | phi>The information of the data position of (2) is sent to the sending device;
the transmitting device and the receiving device discard the measurement result as empty,
Or | phi>The corresponding data;
the sending device and the receiving device carry out parameter estimation according to the reserved data of the preset part to obtain an error rate; and when the error rate is not greater than the preset threshold value, the transmitting device and the receiving device carry out error correction and privacy amplification to obtain a secret key.
9. The method of claim 8, wherein:
the two groups of different measuring bases are a straight measuring base and an inclined measuring base.
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