CN112039658A - Quantum key distribution method using orbital angular momentum coding - Google Patents

Abstract

The invention discloses a quantum key distribution method using orbital angular momentum encoding, which comprises the following steps: step 1, constructing a QKD protocol model which is irrelevant to a general measuring device, wherein Alice and Bob are both parties of legal communication needing to establish secure key sharing, and Charlie is an untrusted third-party measuring device; step 2, the third party completes Bell state measurement of the auxiliary photons and sends the measurement result to Alice and Bob through a classical public channel; step 3, the two communication parties obtain a key seed according to the measurement result; step 4, repeating the steps 1-3 to obtain a key seed with enough length; step 5, generating a Fibonacci key matrix with the same rank; and 6, verifying whether the key matrix is correct or not. The invention has the advantages that: (1) no adjustment of the system reference frame is required. (2) No flipping of the qubits is required. (3) And a high-capacity coding mode is used, so that the entangled photon coding capacity is improved. (4) With a high data transmission rate.

Description

A Quantum Key Distribution Method Using Orbital Angular Momentum Coding

technical field

The invention relates to a quantum key distribution method using orbital angular momentum coding, and belongs to the technical field of communication networks.

Background technique

Quantum Key Distribution (QKD) technology is a relatively mature branch of quantum communication, and it is used to design and experiment some miniaturized QKD networks with a limited number of nodes, especially QKD networks based on quantum satellites Increase the communication distance. Although quantum satellites have overcome the problem of long-distance photon loss, the real-time omni-directional coverage and multi-node construction of communication remain to be solved, limiting their practical application range. In addition, establishing a complete quantum satellite communication network in space requires a lot of manpower, material resources and time. In recent years, researchers have begun to study the low-altitude airborne QKD platform. This network deployment method has the remarkable characteristics of simple structure, convenient operation and low cost, and will have broad application prospects in the future quantum communication network.

In a fiber channel-based QKD system, the birefringence phenomenon and attenuation effect in the fiber will limit the safe distance of key distribution, which generally can only reach about 100 kilometers. Achieving quantum key distribution over longer distances requires the use of other methods. In a free-space channel, the information-carrying optical signal can essentially ignore birefringence, and the decoherence effect is small. In addition, the optical signal band used in the experiment has good transmission properties and low loss in free space, and the related detector technology is gradually mature. However, the free space QKD near the ground is still affected by atmospheric turbulence, weather conditions, and terrain, and it is also impossible to achieve a longer safe transmission distance. With the research on aircraft technology and quantum satellites, researchers plan to use earth satellites or other space platforms as relay nodes to achieve longer-distance and even global QKD networks, especially in a vacuum environment, where optical signals can be almost lossless. transmission. Using Orbital Angular Momentum (OAM) to encode quantum information has two advantages: First, the OAM state is rotationally invariant in the transmission direction, so the sender and receiver do not have to adjust the reference system in real time. Second, OAM theoretically has infinite-dimensional eigenstates, and the use of high-dimensional coding can greatly improve the coding efficiency of the system.

In recent years, orbital angular momentum technology has developed rapidly, such as key technologies such as generation, control and interface with other systems. Furthermore, Yu et al. proposed the use of a planar plasmonic interface to generate beams in a single OAM state. The study also shows that unique scattering resonances in nanoplasmonic helical arrays can support photonic band gaps with band-edge modes with multiple OAM values distributed between Fibonacci numbers. Therefore, people began to study the high-capacity quantum key distribution scheme, and made some progress. Research on high-capacity quantum key distribution schemes by developing high-dimensional Hilbert spaces has two main advantages: On the one hand, multiple bits of a shared key can be encoded on a quantum. On the other hand, high-dimensional systems are more robust to certain types of noise. In 2013, Simon et al. proposed a high-capacity, high-efficiency form of quantum key distribution scheme. They used the specially designed OAM entanglement state of light and Fibonacci sequence to realize quantum key distribution. The transmission capacity of single quantum information of this scheme is further increased, but the high-capacity characteristics of its scheme are still difficult to realize, and the encoding is not enough. Flexible restrictions. The problem with this scheme is mainly because increasing the information capacity depends on OAM with larger bandwidth and the method used for encoding, so it is impossible to satisfy both longer transmission distance and lower bit error rate due to the limitation of practical bandwidth . Secondly, although the theoretical analysis of the OAM-QKD protocol by Simon et al. has been proposed, due to the defects in the hardware equipment of the practical application system, it may still suffer from photon number separation attacks and blinding attacks. In 2012, Lo et al. proposed the use of measurement device independence to solve the problem of measurement-side vulnerabilities. In the Measurement-device-independent QKD (MDI-QKD) protocol, both legitimate communication parties (Alice and Bob) send quantum key information to a third party (Charlie) to complete the Bell measurement, even if Charlie is not trusted , can also complete a secure QKD process. And in this system, the transmission distance of Alice or Bob's information is only the distance from Alice or Bob's information to the detector, so the communication distance between Alice and Bob is twice the actual transmission distance in QKD.

Quantum OAM can generate OAM values with multiple distributions between Fibonacci numbers through nanoplasmonic helical arrays. Based on the above characteristics of OAM, the present invention provides an OAM-MDI-QKD scheme encoded by the relationship between Fibonacci sequence and Lucas sequence. Information transfer capacity for quantum key distribution.

SUMMARY OF THE INVENTION

The technology of the present invention solves the problem: in the QKD system using the optical fiber channel, the birefringence phenomenon and the attenuation effect existing in the optical fiber will limit the safe distance of key distribution, while in the free space channel, the optical signal carrying the information can basically Birefringence is ignored and decoherence effects are small. In addition, the optical signal band has good transmission properties and low loss in free space, and the related detector technology is gradually mature. However, the free space QKD near the ground will be affected by atmospheric turbulence, weather conditions and terrain, and it is also impossible to achieve a longer safe transmission distance. How to improve the transmission capacity of single-shot quantum information without increasing additional bandwidth is a key problem that must be solved to realize the practicality of QKD technology.

The technical scheme adopted by the present invention is: a quantum key distribution method using orbital angular momentum encoding, which comprises the following steps:

Bob使用卢卡斯(lucas)值编码OAM纠缠光子对，记为|φ>。OAM纠缠态中存在的两种光子态分别命名为Fibonacci值的信号(signal)光子态和辅助(idler)光子态，其中信号光子态记为|F_k>_s，辅助光子态记为|F_k>_i，其中k为正整数。Alice和Bob分别将纠缠对中信号光子留给自己。与此同时，Alice和Bob分别将调制好的辅助光子通过自由空间信道发送给第三方测量设备Charlie。Step 1. Build a general measurement device-independent QKD protocol model, in which Alice and Bob are legitimate communication parties who need to establish secure key sharing, and are responsible for preparing photonic information. And Charlie is an untrusted third-party measurement device that detects the entangled photons transmitted by Alice and Bob. Alice uses Fibonacci values to encode OAM entangled photon pairs, denoted as

Bob uses the Lucas value to encode the OAM entangled photon pair, denoted by |φ>. The two photon states existing in the OAM entangled state are named as the signal photon state and the auxiliary (idler) photon state of the Fibonacci value, respectively, where the signal photon state is denoted as |F _k > _s , and the auxiliary photon state is denoted as |F _k > _i , where k is a positive integer. Alice and Bob each keep the signal photons in the entangled pair to themselves. At the same time, Alice and Bob respectively send the modulated auxiliary photons to Charlie, a third-party measurement device, through the free space channel.

和

并阻止任何非Fibonacci值的OAM态通过。L_C1、D_C1、L_C2和D_C2是四个单光子探测器，用于检测Fibonacci值的OAM态，其中L_C1用于检测OAM态|F_k-2>/|F_k-1>；L_C2用于检测OAM态|F_k-1>/|F_k+1>；D_C1用于检测OAM叠加态

D_C2用于检测OAM叠加态

然后，当且仅当L_C1和L_C2、L_C1和D_C2、D_C1和L_C2、D_C1和D_C2四种情况中任一种情况下的两个探测器同时触发时，本次测量成功。最后，Charlie完成了对辅助光子的Bell态测量，并将测量结果通过经典公开信道发送给Alice和Bob。Step 2. In Charlie's measurement device, first use two static optical OAM sorters (Sorter) and a lens to filter out the superposition state

and

and prevents any OAM states of non-Fibonacci values from passing through. L _C1 , D _C1 , L _C2 and D _C2 are four single-photon detectors for detecting OAM states of Fibonacci values, where L _C1 is used to detect OAM states |F _k-2 >/|F _k-1 >; L _C2 is used to detect the OAM state |F _k-1 >/|F _k+1 >; D _C1 is used to detect the OAM superposition state

D _C2 is used to detect OAM superposition states

Then, if and only if the two detectors in any of the four cases L _C1 and L _C2 , L _C1 and D _C2 , D _C1 and L _C2 , D _C1 and D _C2 fire at the same time, this measurement success. Finally, Charlie completes the Bell state measurement of the auxiliary photon and sends the measurement result to Alice and Bob through the classical open channel.

和Charlie的测量结果，使用公式F_k＝F_k-1+F_k-2,k≥2，k为整数，得到用于生成密钥信息的Fibonacci值，记为F_k。同时，Bob检测到一个确定的Fibonacci值时，可以根据lucas编码的OAM纠缠态公式|φ>和Charlie的测量结果，使用公式L_k＝F_k+1+F_k-1,k≥2，k为整数，得到用于生成密钥信息的lucas值，记为L_k。然后，Alice和Bob根据Fibonacci序列和Lucas序列可以同时得到F_k和L_k，进一步得到密钥种子F_2k＝F_k×L_k。上述过程不需要交换经典信息，也不需要进行比特位翻转。Step 3. According to the measurement results, Alice and Bob keep all the results corresponding to Charlie's successful measurement. Then, Alice modulates the locally reserved signal photons and transmits them to the local LA detector, and Bob also modulates and transmits the locally reserved signal photons to the local _{LB detector} . Alice and Bob use the OAM sorter LA or _LB , respectively, to _detect the signal photon state. If Alice or Bob find that the results published by Charlie do not match what they detected, both parties will terminate the communication. Otherwise, they will perform the actions described below. Alice and Bob, two legitimate communication parties, when one party detects the definite Fibonacci value, the Fibonacci value detected by the other party is still uncertain. When Alice detects a definite Fibonacci value, it can entangle according to the Fibonacci-encoded OAM formula

and Charlie's measurement result, using the formula F _k =F _k-1 +F _k-2 , k≥2, k is an integer, to obtain the Fibonacci value for generating key information, denoted as F _k . At the same time, when Bob detects a certain Fibonacci value, he can use the formula L _k =F _k+1 +F _k-1 , k≥2, k is an integer, and the lucas value used to generate the key information is obtained, denoted as L _k . Then, Alice and Bob can obtain F _k and L _k at the same time according to the Fibonacci sequence and the Lucas sequence, and further obtain the key seed F _2k =F _k ×L _k . The above process does not require the exchange of classical information, nor does it require bit flipping.

Step 4. Alice and Bob repeat steps 1-3 until a long enough key seed is obtained.

Step 5. According to the results of Charlie's detector, Alice and Bob obtain the key seed F _2k of the Fibonacci key matrix. Then, they used a random number generator to generate a Fibonacci key matrix with the same rank.

Step 6. Alice and Bob can verify whether the key matrix is correct through the determinant det(D _2k )=1 corresponding to the Fibonacci key matrix. If the rank of the determinant is not equal to 1, the communication is terminated. Otherwise, they can encrypt digital messages by matrix multiplication using the Fibonacci diagonal key matrix.

The invention takes full advantage of the high-dimensional characteristics of quantum orbital angular momentum, designs a quantum key distribution method using orbital angular momentum encoding, uses Fibonacci numbers and Lucas numbers to encode quantum information, and uses Fibonacci numbers to encode quantum information. The relationship between the sequence and the Lucas sequence decodes the key information, increasing the information capacity of a single quantum key distribution.

The advantages of the present invention compared with the prior art are:

(1) The present invention does not need to adjust the system reference frame. In the QKD system based on OAM coding, because the OAM state is rotationally invariant in the transmission direction, the system does not need to monitor and adjust the reference frame in real time.

(2) The present invention does not need to flip the qubit. Alice and Bob, both communicating parties, can obtain the key seed according to their own sorting machines LA and _LB , and get the measurement result from Charlie, instead of the bit flip method used in the original MDI _- QKD protocol.

(3) The present invention uses a high-capacity encoding method. Using the obtained Fibonacci values as seeds for the Fibonacci block diagonal matrix, the sequence of digital messages can then be encrypted using matrix multiplication. In the Simon et al. protocol, each Fibonacci value is used to represent a three-digit binary string. In the present invention, the same Fibonacci number is used to construct the Fibonacci diagonal matrix, and the Fibonacci block diagonal matrix is further constructed with the Lucas number from Bob, and the generated key is obviously longer than that encoded as a three-digit binary string. The invention improves the encoding ability of entangled photons.

(4) The present invention has a high data transmission rate. Sorters LA and LB were placed at Alice's end and Bob's end, respectively, and two pairs of detectors, _{L C1} and _{D C1} , L _C2 and D _C2 , were placed in Charlie's measurement device. Unlike the original MDI-QKD protocol proposed by Lo et al., key information is generated for each probe result and neither case is discarded. That is, in Charlie's measurement device, when any of L _C1 and L _C2 , L _C1 and D _C2 , D _C1 and L _C2 , and D _C1 and D _C2 respond to the detectors, both Alice and Bob can obtain the secret key information.

Description of drawings

Fig. 1 is the experimental schematic diagram of the OAM-MDI-QKD scheme based on Fibonacci coding of the present invention;

The symbols in the figure are explained as follows:

Alice and Bob are legitimate communication parties;

Charlie is an untrusted third-party measurement device;

L _C1 , D _C1 , L _C2 and D _C2 are four single-photon detectors;

Sorter is a photonic OAM state sorter;

BS is a beam splitter;

L _A and L _B are the OAM state sorters at the Alice end and the Bob end, respectively;

Decoy-IM is a decoy state intensity modulator;

SLM is a spatial light modulator;

l is a quantum superposition state with Fibonacci sequence characteristics and Lucas sequence characteristics generated by photonic OAM;

|F _k-1 > _A , |F _k-2 > _A and |F _k+1 > _B , |F _k-1 > _B are the signal photon states and stay in the local (Alice or Bob);

|F _k-2 > _B , |F _k-1 > _B and |F _k-1 > _A , |F _k+1 > _A are auxiliary photon states, which are sent to a third party (Charlie) for measurement.

Detailed ways

A quantum key distribution method using orbital angular momentum coding proposed by the present invention needs to solve the following two problems: (1) In the classical quantum key distribution protocol, the transmission capacity of a single quantum information is mostly 1 bit The choice of horizontal and vertical basis vectors to encode quantum information under polarization coding cannot effectively increase the information capacity. How to change the encoding method of quantum information to increase the capacity of single quantum information transmission in key distribution is the first and foremost problem that must be solved. Problems; (2) The quantum key distribution scheme cannot quickly enter the practical stage. One of the main reasons is the uncertainty of the quantum measurement process, which leads to the low efficiency of the overall scheme. In the entanglement protocol (Ekert91 protocol), the efficiency factor q = 1/2. How to improve the efficiency of quantum key distribution scheme is a key technology for its practical application.

The main realization idea of the present invention is to fully utilize the high-dimensional characteristics of quantum OAM, use Fibonacci sequence to encode quantum information, and design a quantum key distribution method using orbital angular momentum encoding.

Fibonacci and Lucas numbers

Fibonacci sequence: F _k =F _k-1 +F _k-2 , k≥2, k is an integer; Lucas sequence: L _k =L _k-1 +L _k-2 , k≥2, k is an integer.

The relationship that exists between them:

L _k =F _k+1 +F _k-1 , F _2k =F _k ×L _k .

Construct a Fibonacci matrix:

Construct the Fibonacci diagonal key matrix:

det(D _2k )=(-1) ^k(k+1) .

The present invention is a quantum key distribution method using orbital angular momentum encoding, and the specific implementation steps of the method are as follows:

Bob使用卢卡斯(lucas)值编码OAM纠缠光子对，记为|φ>。OAM纠缠态中存在的两种光子态分别命名为Fibonacci值的信号(signal)光子态和辅助(idler)光子态，其中信号光子态记为|F_k>_s，辅助光子态记为|F_k>_i，其中k为正整数。Fibonacci值和lucas值的OAM纠缠态如下所示：Step 1. Build a general measurement device-independent QKD protocol model, in which Alice and Bob are legitimate communication parties who need to establish secure key sharing, and are responsible for preparing photonic information. And Charlie is an untrusted third-party measurement device that detects the entangled photons transmitted by Alice and Bob. Alice uses Fibonacci values to encode OAM entangled photon pairs, denoted as

Bob uses the Lucas value to encode the OAM entangled photon pair, denoted by |φ>. The two photon states existing in the OAM entangled state are named as the signal photon state and the auxiliary (idler) photon state of the Fibonacci value, respectively, where the signal photon state is denoted as |F _k > _s , and the auxiliary photon state is denoted as |F _k > _i , where k is a positive integer. The OAM entangled states of Fibonacci and lucas values are as follows:

Alice and Bob each keep the signal photons in the entangled pair to themselves. At the same time, Alice and Bob respectively send the modulated auxiliary photons to Charlie, a third-party measurement device, through the free space channel.

和

并阻止任何非Fibonacci值的OAM态通过。L_C1、D_C1、L_C2和D_C2是四个单光子探测器，用于检测Fibonacci值的OAM态，其中L_C1用于检测OAM态|F_k-2>/|F_k-1>；L_C2用于检测OAM态|F_k-1>/|F_k+1>；D_C1用于检测OAM叠加态

D_C2用于检测OAM叠加态

然后，当且仅当L_C1和L_C2、L_C1和D_C2、D_C1和L_C2、D_C1和D_C2四种情况中任一种情况下的两个探测器同时触发时，本次测量成功。最后，Charlie完成了对辅助光子的Bell态测量，并将测量结果通过经典公开信道发送Alice和Bob。Step 2. In Charlie's measurement equipment, first use two static optical OAM sorters (Sorter) and a lens to filter out the superposition state respectively

and

and prevents any OAM states of non-Fibonacci values from passing through. L _C1 , D _C1 , L _C2 and D _C2 are four single-photon detectors for detecting OAM states of Fibonacci values, where L _C1 is used to detect OAM states |F _k-2 >/|F _k-1 >; L _C2 is used to detect the OAM state |F _k-1 >/|F _k+1 >; D _C1 is used to detect the OAM superposition state

D _C2 is used to detect OAM superposition states

Then, if and only if the two detectors in any of the four cases L _C1 and L _C2 , L _C1 and D _C2 , D _C1 and L _C2 , D _C1 and D _C2 fire at the same time, this measurement success. Finally, Charlie completed the Bell state measurement of the auxiliary photon, and sent the measurement result to Alice and Bob through the classical open channel.

Table 1 Possible measurement results of key information in OAM-MDI-QKD scheme

In Table 1, when Charlie performs the Bell state measurement, T means that the detectors L _C1 and L _C2 respond simultaneously; U means that the detectors L _C1 and D _C2 respond simultaneously; V means that the detectors D _C1 and L _C2 respond simultaneously; W means that the detectors D C1 and L C2 respond simultaneously; Detectors D _C1 and D _C2 respond simultaneously.

Step 3. According to the possible measurement results given in Table 1, Alice and Bob keep all the results (T, U, V and W) corresponding to Charlie's successful measurement. Then, Alice modulates the locally reserved signal photons and transmits them to the local LA detector, and Bob also modulates and transmits the locally reserved signal photons to the local _{LB detector} . Alice and Bob use the OAM sorter LA or _LB , respectively, to _detect the signal photon state. If Alice (or Bob) finds that the results published by Charlie do not match what they detected, both parties will terminate the communication. Otherwise, they proceed to do the following.

Table 2 Possible output results of this scheme

可知发送的辅助光子的值为F_k-2，对比Charlie公布的测量结果和响应的探测器，此次通信正常。Alice根据公式F_k＝F_k-1+F_k-2,k≥2可以求出Fibonacci数值F_k。同理，Bob方拥有的Fibonacci数值为F_k-1，根据OAM纠缠态

可知发送的辅助光子的值为F_k+1，对比Charlie公布的测量结果和响应的探测器，此次通信正常。Bob根据公式L_k＝F_k+1+F_k-1,k≥2可以求出Lucas数值L_k。然后，Alice和Bob根据Fibonacci序列和Lucas序列可以同时得到F_k和L_k，进一步得到密钥种子F_2k＝F_k×L_k。上述过程不需要交换经典信息，也不需要进行比特位翻转。当Alice和Bob检测到的结果为其他情况时，如表2中所示，通信双方也可以使用上述相同的方法得到密钥种子F_2k。Among the two communicating parties, when one party detects the definite Fibonacci value, the Fibonacci value detected by the other party still cannot be determined. By analyzing Figure 1, the OAM entanglement state of both communication parties and Charlie's measurement results (as shown in Table 2), both parties can obtain the determined Fibonacci value. For example, if Alice and Bob detect |F _k-1 > and |F _k-1 >, respectively, and the responding detectors in Charlie are L _C1 and L _C2 , the measurement is |F _k-2 > and |F _k+1 >, corresponding to the first possible case in Table 2. The Fibonacci value owned by Alice's side is F _k-1 , according to the OAM entangled state

It can be seen that the value of the auxiliary photon sent is F _k-2 . Comparing the measurement results published by Charlie and the responding detector, the communication is normal. Alice can obtain the Fibonacci value F _k according to the formula F _k =F _k-1 +F _k-2 , k≥2. Similarly, the Fibonacci value owned by Bob's side is F _k-1 , according to the OAM entangled state

It can be seen that the value of the auxiliary photon sent is F _k+1 . Comparing the measurement results published by Charlie and the responding detector, the communication is normal. Bob can calculate the Lucas value L _k according to the formula L _k =F _k+1 +F _k-1 , k≥2. Then, Alice and Bob can obtain F _k and L _k at the same time according to the Fibonacci sequence and the Lucas sequence, and further obtain the key seed F _2k =F _k ×L _k . The above process does not require the exchange of classical information, nor does it require bit flipping. When the results detected by Alice and Bob are other cases, as shown in Table 2, the two communicating parties can also obtain the key seed F _2k using the same method as above.

Step 4. Alice and Bob repeat steps 1-3 until a long enough key seed is obtained (for example: according to Shannon's one-time pad encryption theory, to achieve unconditional security, the key generated by quantum key distribution should be the same as the plaintext, etc. long, and guarantees that a different key is used for plaintext encryption each time).

Step 5. According to the results of Charlie's detector, Alice and Bob obtain the key seed F _2k of the Fibonacci key matrix. Then, they used a random number generator to generate a Fibonacci key matrix with the same rank.

Step 6. Alice and Bob can verify whether the key matrix is correct through the determinant det(D _2k )=1 corresponding to the Fibonacci key matrix. If the rank of the determinant is not equal to 1, the communication is terminated. Otherwise, they can encrypt digital messages by matrix multiplication using the Fibonacci diagonal key matrix.

The present invention is an improved MDI-QKD scheme based on OAM coding, which is carried out on the basis of the original MDI-QKD protocol. The improved scheme is different from the original scheme in two points: 1) In the improved scheme, different l values are used. This method does not weaken the security of the protocol. The security proof of OAM application in quantum communication is detailed in the literature of Simon et al. In addition, the use of OAM state coding can avoid the problem of base dependence, improve the performance of the photon preparation stage, and make the key rate no longer affected by this defect. 2) The second difference is that at the detector side, due to the different settings of the base, the corresponding measurement devices and methods are also different. The main reason why the original MDI-QKD protocol can eliminate eavesdropping on the detector side is that it does not depend on the measurement equipment. The measurement device only publishes the measurement results, and the generation of the security key also requires operations such as bit flipping. The measuring device of the present invention is functionally the same as the original MDI-QKD protocol of Lo et al. It can be seen from the above analysis that the core of the security of the MDI-QKD protocol lies in post-select and bit-flip, There is no change in post selection in the improved scheme, so from the principle of the protocol, the improved scheme does not weaken the security performance of the original MDI-QKD protocol.

In the practical application of the QKD system, because the ideal single-photon source is difficult to achieve, other light sources are generally used instead. When non-ideal light sources are used, they may be eavesdropped by means of photon splitting attacks, so it is generally necessary to introduce decoy state technology. The MDI-QKD polarization coding scheme proposed by Lo et al. applies weakly coherent light sources and decoy states in practical implementation, and some security evidences can be found from this scheme, such as GLLP, Shor-Preskill, and mutual unbiased basis. Similarly, in the MDI-QKD protocol scheme based on OAM coding, if non-ideal light source and decoy state technology are used, its security can also be guaranteed by GLLP, Shor-Preskill, etc., and its security is equivalent to the original scheme.

Contents that are not described in detail in the specification of the present invention belong to the prior art known to those skilled in the art.

The above is only a preferred embodiment of a quantum key distribution method using orbital angular momentum encoding according to the present invention. Under the premise of the principle of the encoded quantum key distribution method, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of a quantum key distribution method using orbital angular momentum encoding of the present invention.

Claims (1)

1. A quantum key distribution method using orbital angular momentum encoding, characterized by: the method comprises the following steps:

step 1, constructing a QKD protocol model which is irrelevant to general measuring equipment, wherein Alice and Bob are both legal communication parties needing to establish secure key sharing and are responsible for preparing photon information; charlie is an untrusted third party measurement device responsible for detecting entangled photons transmitted by Alice and Bob; alice encodes OAM entangled photon pairs using Fibonacci values, noted

Bob encodes OAM entangled photon pairs using Lucas values, denoted as φ>(ii) a Two photon states existing in the OAM entangled state are respectively named as a signal photon state and an auxiliary photon state of Fibonacci value, wherein the signal photon state is marked as | F_k>_sThe auxiliary photon state is denoted as | F_k>_iWherein k is a positive integer; respectively reserving the entanglement centering signal photons for Alice and Bob; meanwhile, Alice and Bob respectively send the modulated auxiliary photons to third-party measuring equipment Charlie through a free space channel;

step 2. in the Charlie measurement equipment, two static optical OAM sorters and a lens are used to filter out the superimposed state

And

and preventing any OAM state of non-Fibonacci values from passing; l is_C1、D_C1、L_C2And D_C2Is four single photon detectors for detecting OAM states of Fibonacci values, wherein L_C1For detecting OAM state | F_k-2>/|F_k-1>；L_C2For detecting OAM state | F_k-1>/|F_k+1>；D_C1For detecting OAM stack states

D_C2For detecting OAM superimposed state

Then, if and only if L_C1And L_C2、L_C1And D_C2、D_C1And L_C2、D_C1And D_C2When two detectors under any one of the four conditions are triggered simultaneously, the measurement is successful; finally, Charlie completes Bell state measurement of the auxiliary photons and sends the measurement result to Alice and Bob through a classical public channel;

step 3, according to the measurement result, Alice and Bob reserve the successful measurement condition of corresponding Charlie in all the results; then, Alice transmits the locally reserved signal photon after modulating the signal photon to the local L_AIn the detector, Bob also modulates and transmits locally reserved signal photons to L of the local side_BIn the detector; alice and Bob use OAM sorter L, respectively_AOr L_BDetecting the signal photon state; if Alice or Bob finds that the result issued by Charlie does not match the result detected by the Charlie, the two communication parties terminate the communication; otherwise, they will perform the following operations; when one party detects the determined Fibonacci value, the other party still cannot determine the detected Fibonacci value; when Alice detects a certain Fibonacci value, it can be based on the Fibonacci encoded OAM entanglement status formula

And Charlie measurements, using formula F_k＝F_k-1+F_k-2K is more than or equal to 2, k is an integer, and a Fibonacci value for generating key information is obtained and is recorded as F_k(ii) a Meanwhile, when Bob detects a certain Fibonacci value, the value can be according to the Lucas coded OAM entanglement state formula | phi>And Charlie measurements, using formula L_k＝F_k+1+F_k-1K is not less than 2, k is an integer, and a lucas value for generating key information is obtained and recorded as L_k(ii) a Then, Alice and Bob can simultaneously obtain F according to the Fibonacci sequence and the Lucas sequence_kAnd L_kGo forward toStep (b) to obtain a key seed F_2k＝F_k×L_k(ii) a The process does not need to exchange classical information and does not need to carry out bit flipping;

step 4, Alice and Bob repeat steps 1-3 until a sufficiently long key seed is obtained;

step 5, according to the result of the Charlie detector, Alice and Bob obtain a key seed F of the Fibonacci key matrix_2k(ii) a Then, they generate Fibonacci key matrices with the same rank using a random number generator;

and 6, enabling Alice and Bob to pass through a determinant det (D) corresponding to the Fibonacci key matrix_2k) Verifying whether the key matrix is correct or not as 1; if the rank of the determinant is not equal to 1, communication is aborted; otherwise, they can encrypt the digital message by matrix multiplication using the Fibonacci diagonal key matrix.

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