A quantum teleportation method based on atom-photon entanglement

Abstract

The application discloses a kind of quantum teleportation methods based on atom-photon entanglement: step 1: Alice and Bob prepare the atom sequence of different initial state.Step 2: Alice generates reference light pulse and signal light pulse, and is transmitted in channel by time division multiplexing.Step 3: Alice manipulates signal light pulse and atom interaction to produce entangled state, and after transmission by quantum channel, coherent light and the atom of Bob establish entanglement, to complete three-particle entanglement.Step 4: Alice divides atom sequence, and Bob carries out channel security detection.Step 5: after channel security, Alice encodes secret information on information sequence atom and publishes measurement result.Step 6: Alice does Hadamard gate operation to the atom sequence carrying information.Step 7: Bob demodulates secret information.The application makes full use of long decoherence time atom-photon entanglement resources, meets the communication demand of high channel capacity and high link efficiency, and provides a feasible way for constructing large-scale, loss-resistant quantum internet.

Description

Technical Field

[0001] This invention belongs to the field of quantum secure communication technology, specifically relating to a quantum teleportation method based on atom-photon entanglement. Background Technology

[0002] Quantum teleportation protocols typically require complex quantum operations and classical communication assistance. In practical systems, decoherent evolution of quantum states caused by channel transmission is unavoidable. Existing entangled sources are primarily pure photons. After long-distance quantum channel transmission in optical fibers or free space, the decoherence time of entangled photon pairs between the communicating parties is short. On the other hand, the link efficiency is low due to the dark count rate of the photon detector.

[0003] Reference 1, “Cardoso FR, Lee J, Checchinato R, et al. Impact of temporalcorrelations, coherence, and postselection on two-photon interference[J]. Physical Review Research, 2025, 7(1): 013190,” clearly verifies the inherent defect of photon entanglement sources, namely that photon pairs generated in a cascade manner carry inherent temporal correlations, which interact with decoherence effects and shorten decoherence time.

[0004] Reference 2, "Zhang S, Shi J, Liang Y, et al. Fast delivery of heralded atom-photon quantum correlation over 12 km fiber through multiplexing enhancement[J]. Nature Communications, 2024, 15(1): 10306," achieved the transmission of atom-photon entangled states over 12 km fiber using multiplexing enhancement technology. However, due to the inherent transmission loss of the fiber and the efficiency loss in the photon collection and detection stages, the quantum entanglement distribution efficiency of the link is low, making it difficult to meet the actual needs of long-distance quantum communication.

[0005] The existing literature indicates that quantum communication protocols are significantly limited by the characteristics of photon transmission. Photons are easily lost during transmission in channels such as optical fibers, resulting in short decoherence times and limiting communication distance and efficiency. In single-photon detection, the presence of dark count rate in the detector leads to low link efficiency. Atom-photon entangled sources have longer decoherence times, enabling long-term storage and high-fidelity manipulation of quantum states, effectively alleviating the problem of excessively rapid decoherence in coherent light transmission. Choosing coherent light as the information carrier offers higher light intensity, more stable transmission characteristics, and stronger resistance to loss, effectively reducing the impact of detection noise such as dark count on system performance, resulting in high link efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a quantum teleportation method based on atom-photon entanglement to solve the problems of short decoherence time and low link efficiency in existing communication protocols.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A quantum teleportation method based on atom-photon entanglement includes the following steps: Step 1: Alice in the atomic cavity C A The initial state of preparation is atomic sequence ( i =1,2,...,N); Bob is in the atomic cavity C B The initial state of preparation is atomic sequence ( i =1,2,...,N); where, and It is an atomic sequence The complex number formed by the area and position of the wave packet of the two bases is denoted as . a i and b i , i Indicates the first atomic number in the sequence i One atom; Step 2: Alice generates a pulse sequence through a pulse width modulation (PWM) driver circuit, and then generates a reference light pulse and a signal light pulse through an amplitude modulation (AM) and a polarization modulation (PM) modulator. The reference light is strongly coherent, and the signal light is denoted as a weakly coherent light sequence. , i =1,2,...,N, This represents the first in a weakly coherent light sequence. i A beam of coherent light, with an initial phase of Through time-division multiplexing, strongly coherent light and weakly coherent light are separated by time intervals. T Transmitted along the same optical path; Step 3: Based on the Faraday rotation effect, Alice controls the weakly coherent light sequence. Entering the atomic cavity C A In and atomic sequence Interacting, outputting atomic sequences Coherent optical sequence of energy level information coherent optical sequence Phase and atomic sequence The energy levels they occupy establish an entangled relationship; For weakly coherent light sequences Weakly coherent light with different polarizations: Left-handed circularly polarized light and right-handed circularly polarized light The output coherent light sequence With atomic sequence The entanglement relationship is established as follows:

[0009] ; Alice then Send it to Bob, who then guides it into the atomic cavity. C B and with atomic sequence The entanglement relationship is established, and the output coherent light sequence is denoted as . Based on the principle of entanglement, atomic sequences , atomic sequence and the output coherent light sequence Establish a three-particle entanglement relationship, namely:

[0010]

[0011] Obviously, regardless of the coherent light input at the Alice end... or After two entanglements, a coherent light sequence is output. The phase is unaffected Polarization has an effect; additionally, due to the energy consumed during the coupling process... Through the entanglement and exchange process, the atomic sequence , atomic sequence and from the cavity C B Output coherent light sequence The formation of a three-particle entangled state can be represented as: ; Step 4: Alice sequences the atoms The sequences were randomly divided into two groups: ( j =1,2,...,C) ( k =1,2,...,M), satisfying Alice selects atomic sequences Perform measurements and sequence the atoms The location is given to Bob, and Bob will then provide the corresponding atomic sequence. Divided into two atomic sequences: ( j =1,2,...,C) ( k =1,2,...,M), satisfying Coherent light sequence Divided into sequences ( j =1,2,...,C) and sequence ( k =1,2,...,M); Bob receives the sequence at the corresponding position at the receiving end. and atomic sequence Measurements were performed by interfering the reference light from the same source with the signal light obtained in step 2; Alice and Bob performed channel security checks, based on... The degree of entanglement is used to verify the entanglement relationship. If the entanglement relationship exists, the channel is secure, and proceed to step 5. Because of the legitimacy of Alice and Bob, Eve cannot obtain the state of the atoms at the ends of Alice and Bob's communication. Therefore, Eve can only eavesdrop on the channel in step 2. Even if Eve obtains the information of coherent light through intercept-retransmission, due to the destruction of the three-particle entanglement, Bob can still detect the abnormal entanglement degree of the three particles through channel security detection and infer the conclusion that the channel has been eavesdropped. If Bob infers that the channel has been eavesdropped, he terminates the communication and returns to step 1. Step 5: Alice controls the phase of the external laser pulse to the first preset phase. , recorded as operation At this point, the remaining atomic sequence The energy level states are Alice performs the following four unitary operations on the atomic sequence. Encode: , , , , recorded as , , , ; Alice controls the phase of the external laser pulse to the second preset phase. , recorded as operation At this point, the remaining atomic sequence The energy level states are Alice performs the following four unitary operations on the atomic sequence. Encode: , , , , recorded as , , , The encoded atomic sequence is denoted as ; The above eight operations are the coding operations performed by Alice. U Alice ; Step 6: To facilitate the analysis of entanglement, Alice processed the atomic sequences carrying information. Perform Hadamard door operations; that is: , ; Step 7: Alice analyzes the atomic sequence The measurement was performed, and the results were announced to Bob; Bob measured the atoms. Based on the measurement results, the coding operations performed by Alice can be inferred. U Alice Subsequently, Bob compared Alice's atomic sequence. Decode to obtain the encoding operation U Alice The corresponding encoding information.

[0012] Furthermore, in step 1, the atomic sequence and atomic sequence The preparation process is as follows: The preparation of a single ground state is insufficient to meet the requirements of high channel capacity. Therefore, a superposition state of a doubly degenerate ground state is prepared using stimulated Raman transitions. Entanglement pairs are manipulated for the superposition state of the "Schrödinger cat". A continuous laser pulse from a Raman beam generates the "Schrödinger cat" superposition state. The atomic energy level state is controlled through quantum mechanical interference between local wave packets. By controlling the duration and phase of the laser pulse acting on the qubit, a phase change of π / 2 radians occurs in the atomic system. This pulse changes the internal state of the atom from... Rotate to and The superposition of states causes the wave packet to split in the location space.

[0013] Furthermore, in step 2, the time-division multiplexing process is as follows: Step 1, Amplitude Modulation: Reference light time slot: AM fully open, outputting a strong coherent light pulse with a power much higher than the signal light to ensure interference contrast; Signal optical time slot: AM attenuation, outputting weakly coherent optical pulses; Step 2, Polarization Modulation: The pulse sequence generated by amplitude modulation is subjected to PM modulation to generate signal light pulses. The reference light time slot and the signal light time slot alternate at time intervals. T It is distributed into the channel and transmitted to Bob's end.

[0014] Furthermore, in step 5: .

[0015] Furthermore, in step 5, the first preset phase Pick Second preset phase Pick Compared with the prior art, the present invention has the following technical advantages: (1) This invention selects the interaction relationship between atoms and photons as the entanglement source, and realizes long-term storage of quantum states by relying on the inherent long coherence time of atoms. Among them, photons have good transmission characteristics and are suitable for long-distance quantum communication; while atoms can realize high-fidelity quantum state manipulation and storage.

[0016] (2) This invention constructs stable atom-photon entangled pairs in a cavity based on Faraday rotation. During the entanglement establishment process, compared to the two-step QSDC protocol, quantum teleportation only requires one detection of the intermediate transmitted photon. Furthermore, coherent light is used instead of single photons as the information carrier, resulting in a detection efficiency far exceeding that of single-photon detection, effectively reducing the impact of transmission loss on link performance. The atom-photon interaction time is 0.053 seconds. much smaller 87The lifetime of the Rb atom's ground state. For single-photon protocols, successful entanglement between two nodes requires the successful detection of a photon; the probability of a photon being emitted and detected by a single node is... ,in k It is the probability of successfully emitting a photon. It is the efficiency of photon detection ( (i.e., low detection efficiency). Therefore, the probability of two nodes successfully establishing entanglement is... For a single photon, under normal circumstances, k =0.2, The success rate of coherent light detection is much higher than that of single-photon detection, typically stabilizing above 90%. Generally, photon loss reduces the resolution of coherent light homodyne detection. Due to absorption and scattering by the cavity mirrors, photon loss within the cavity is unavoidable, resulting in approximately 6% loss. The failure rate due to atomic attenuation is approximately 2%, thus affecting the probability of successful entanglement. p suss = On the other hand, channel attenuation is the dominant photon loss, which is the same as in the single-photon analysis process, because... The distribution is symmetrical about the midpoint, and considering channel loss, the success probability of perfect detection is 1 / 2. Based on the high detection efficiency of coherent light, its link efficiency can be improved by two orders of magnitude compared with traditional single-photon and atomic entanglement protocols, far exceeding the link efficiency threshold of 1.381.

[0017] In an atom-photon-atom entangled system, assuming that non-entangled states are provided in all cycles attempting to generate entanglement, the fidelity is denoted as... ,when That is, when the system is in the maximum mixing state, the average maximum fidelity of the representation of the protocol can be obtained. , Assuming the protocol allows the transmission of entangled states within a specified time, it has a finite probability of success. When At that time, the deterministic fidelity of the system is denoted as In other words, at the predetermined time point, regardless of whether entanglement generation is successful or not, This represents the average fidelity of the output quantum state. Figure 1The simulation diagram shows the link efficiency and fidelity in this invention. Compared with the entanglement of atoms and single photons in reference 3, "Zhang S, Shi J, Liang Y, et al. Fast delivery of heralded atom-photon quantum correlation over 12 km fiber through multiplexing enhancement[J]. Nature Communications, 2024, 15(1): 10306.", the link efficiency of the method in this invention corresponds to higher fidelity. Therefore, the communication protocol designed by the method of this invention meets the requirements of high-fidelity communication and provides a feasible way to build a large-scale, loss-resistant quantum internet. Attached Figure Description

[0018] Figure 1 This paper presents a simulation comparison of the quantum teleportation method based on atom-photon entanglement of the present invention with the link efficiency in reference 3. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and examples, so that those skilled in the art can better understand the present invention.

[0020] This example presents a quantum teleportation method based on atom-photon entanglement, including the following steps: Step 1: Alice in the atomic cavity C A The initial state of preparation is atomic sequence ( i =1,2,...,N); Bob is in the atomic cavity C B The initial state of preparation is atomic sequence ( i =1,2,...,N); where, and It is an atomic sequence The complex number formed by the area and position of the wave packet of the two bases is denoted as . a i and b i , i Indicates the first atomic number in the sequence i One atom.

[0021] atomic sequence and atomic sequence The fabrication process involves the following steps: A superposition of "Schrödinger cat" states is generated using continuous laser pulses from a Raman beam; the atomic energy level states are manipulated through quantum mechanical interference between local wave packets; by controlling the duration and phase of the laser pulses acting on the qubits, a phase change of π / 2 radians is achieved in the atomic system. This pulse changes the internal state of the atom from... Rotate to and The superposition of states causes the wave packet to split in the location space.

[0022] Step 2: Alice generates a pulse sequence through a pulse width modulation (PWM) driver circuit, and then generates a reference light pulse and a signal light pulse through an amplitude modulation (AM) and a polarization modulation (PM) modulator. The reference light is strongly coherent, and the signal light is denoted as a weakly coherent light sequence. , i =1,2,...,N, This represents the first in a weakly coherent light sequence. i A beam of coherent light, with an initial phase of Through time-division multiplexing, strongly coherent light and weakly coherent light are separated by time intervals. T Transmitted along the same optical path; The time-division multiplexing process is as follows: Step 1, Amplitude Modulation: Reference light time slot: AM fully open, outputting a strong coherent light pulse with a power much higher than the signal light to ensure interference contrast; Signal optical time slot: AM attenuation, outputting weakly coherent optical pulses; Step 2, Polarization Modulation: The pulse sequence generated by amplitude modulation is subjected to PM modulation to generate signal light pulses. The reference light time slot and the signal light time slot alternate at time intervals. T It is distributed into the channel and transmitted to Bob's end.

[0023] Step 3: Based on the Faraday rotation effect, Alice controls the weakly coherent light sequence. Entering the atomic cavity C A In and atomic sequence Interacting, outputting atomic sequences Coherent optical sequence of energy level information coherent optical sequence Phase and atomic sequence The energy levels they occupy establish an entangled relationship; For weakly coherent light sequences Weakly coherent light with different polarizations: Left-handed circularly polarized light and right-handed circularly polarized light The output coherent light sequence With atomic sequence The entanglement relationship is established as follows:

[0024] ; Alice then Send it to Bob, who then guides it into the atomic cavity. C B and with atomic sequence The entanglement relationship is established, and the output coherent light sequence is denoted as . Based on the principle of entanglement, atomic sequences , atomic sequence and the output coherent light sequence Establish a three-particle entanglement relationship, namely:

[0025]

[0026] Through the entanglement and exchange process, the atomic sequence , atomic sequence and from the cavity C B Output coherent light The formation of a three-particle entangled state can be represented as: ; Step 4: Alice sequences the atoms The sequences were randomly divided into two groups: ( j =1,2,...,C) ( k =1,2,...,M), satisfying Alice selects atomic sequences Perform measurements and sequence the atoms The location is told to Bob, and Bob will then provide the corresponding atomic sequence. Randomly divided into two atomic sequences: ( j =1,2,...,C) ( k =1,2,...,M), satisfying Coherent light sequence Divided into sequences ( j =1,2,...,C) and sequence ( k=1,2,...,M); Bob receives the sequence at the corresponding position at the receiving end. and atomic sequence Measurements were performed by interfering the reference light from the same source with the signal light obtained in step 2; Alice and Bob performed channel security checks, based on... The degree of entanglement is used to verify the entanglement relationship. If the entanglement relationship exists, the channel is secure, and proceed to step 5. If Bob deduces that the channel is being eavesdropped on, he terminates the communication and returns to step 1. Step 5: Alice controls the phase of the external laser pulse to the first preset phase. (In this embodiment, we take) ), denoted as operation At this point, the remaining atomic sequence The energy level states are Alice performs the following four unitary operations on the atomic sequence. Encode: , , , , recorded as , , , ; Alice controls the phase of the external laser pulse to the second preset phase. (In this embodiment, we take) ), denoted as operation At this point, the remaining atomic sequence The energy level states are Alice performs the following four unitary operations on the atomic sequence. Encode: , , , , recorded as , , , The encoded atomic sequence is denoted as ; The above eight operations are the coding operations performed by Alice. U Alice ; ; Step 6: Alice processes the atomic sequence carrying the information. Perform Hadamard door operations; that is: , ; Step 7: Alice analyzes the atomic sequence The measurement was performed, and the results were announced to Bob; Bob measured the atoms. Based on the measurement results, the coding operations performed by Alice can be inferred. U Alice Subsequently, Bob compared Alice's atomic sequence. Decode to obtain the encoding operation U Alice The corresponding encoding information.

[0027] Specifically, and The corresponding information for the operation is "0" or "1". U 1. U 2. U 3 and U The four operations correspond to the information "00", "01", "10", and "11" respectively. Bob performs the operations according to the codes. , , , , , , , The resulting encoding information is 000~111.

[0028] The quantum teleportation method based on atom-photon entanglement presented in this embodiment requires only one detection of the intermediate photon during the entanglement establishment process, compared to the two-step QSDC protocol. Furthermore, coherent light is used instead of single photons as the information carrier, resulting in significantly higher detection efficiency than single-photon detection, effectively reducing the impact of transmission loss on link performance. The atom-photon interaction time is 0.053 seconds. much smaller 87 The lifetime of the Rb atom's ground state. For single-photon protocols, successful entanglement between two nodes requires the successful detection of a photon; the probability of a photon being emitted and detected by a single node is... ,in k It is the probability of successfully emitting a photon. It is the efficiency of photon detection ( (i.e., low detection efficiency). Therefore, the probability of two nodes successfully establishing entanglement is... For a single photon, under normal circumstances, k =0.2, The success rate of coherent light detection is much higher than that of single-photon detection, typically stabilizing above 90%. Generally, photon loss reduces the resolution of coherent light homodyne detection. Due to absorption and scattering by the cavity mirrors, photon loss within the cavity is unavoidable, resulting in approximately 6% loss. The failure rate due to atomic attenuation is approximately 2%, thus affecting the probability of successful entanglement. p suss = On the other hand, channel attenuation is the dominant photon loss, which is the same as in the single-photon analysis process, because... The distribution is symmetrical about the midpoint, and considering channel loss, the success probability of perfect detection is 1 / 2. Based on the high detection efficiency of coherent light, its link efficiency can be improved by two orders of magnitude compared with traditional single-photon and atomic entanglement protocols, far exceeding the link efficiency threshold of 1.381.

[0029] The quantum teleportation method based on atom-photon entanglement presented in this embodiment includes a sender Alice, a receiver Bob, and a quantum channel for transmitting information. Alice manipulates coherent light to interact with atoms to prepare atom-photon entangled pairs, divides the detection sequence and the information sequence, sends the coherent light from the entangled pair to Bob, and re-establishes the entanglement relationship. Bob completes security detection by measuring the detection sequence and the corresponding entangled photons. After mutual confirmation that the channel is secure and there is no eavesdropping, Alice performs encoding operations on the atoms of the information sequence and publishes the measurement results. After confirming that the channel has not been interrupted by interference, Bob combines the previous measurement data and decodes the confidential information through unitary transformation.

Claims

1. A method for quantum teleportation based on atomic-photon entanglement, characterized in that, Includes the following steps: Step 1: Alice in the atomic cavity C A The initial state of preparation is atomic sequence ( i =1,2,...,N); Bob is in the atomic cavity C B The initial state of preparation is atomic sequence ( i =1,2,...,N); where, and It is an atomic sequence The complex number formed by the area and position of the wave packet of the two bases is denoted as . a i and b i , i Indicates the first atomic number in the sequence i One atom; Step 2: Alice generates a pulse sequence through a pulse width modulation driving circuit, and then generates a reference light pulse and a signal light pulse through an amplitude modulator and a polarization modulator. The reference light is strongly coherent light, and the signal light is denoted as a weakly coherent light sequence. , i =1,2,...,N, This represents the first in a weakly coherent light sequence. i A beam of coherent light, with an initial phase of Through time-division multiplexing, strongly coherent light and weakly coherent light are separated by time intervals. T Transmitted along the same optical path; Step 3: Based on the Faraday rotation effect, Alice controls the weakly coherent light sequence. Entering the atomic cavity C A In and atomic sequence Interacting, outputting atomic sequences Coherent optical sequence of energy level information coherent optical sequence Phase and atomic sequence The energy levels they occupy establish an entangled relationship; For weakly coherent light sequences Weakly coherent light with different polarizations: Left-handed circularly polarized light and right-handed circularly polarized light The output coherent light sequence With atomic sequence The entanglement relationship is established as follows: ； Alice then Send it to Bob, who then guides it into the atomic cavity. C B and with atomic sequence The entanglement relationship is established, and the output coherent light sequence is denoted as . Based on the principle of entanglement, atomic sequences , atomic sequence and the output coherent light sequence Establish a three-particle entanglement relationship, namely: Through the entanglement and exchange process, the atomic sequence , atomic sequence and from the cavity C B Output coherent light sequence The formation of a three-particle entangled state can be represented as: ； Step 4: Alice sequences the atoms The sequences were randomly divided into two groups: ( j =1,2,...,C) ( k =1,2,...,M), satisfying Alice selects atomic sequences Perform measurements and sequence the atoms The location is given to Bob, and Bob will then provide the corresponding atomic sequence. Divided into two atomic sequences: ( j =1,2,...,C) ( k =1,2,...,M), satisfying Coherent light sequence Divided into sequences ( j =1,2,...,C) and sequence ( k =1,2,...,M); Bob receives the sequence at the corresponding position at the receiving end. and atomic sequence Measurements were performed by interfering the reference light from the same source with the signal light obtained in step 2; Alice and Bob performed channel security checks, based on... The degree of entanglement is used to verify the entanglement relationship. If the entanglement relationship exists, the channel is secure, and proceed to step 5. If Bob deduces that the channel is being eavesdropped on, he terminates the communication and returns to step 1. Step 5: Alice controls the phase of the external laser pulse to the first preset phase. , recorded as operation At this point, the remaining atomic sequence The energy level states are Alice performs the following four unitary operations on the atomic sequence. Encode: , , , , recorded as , , , ; Alice controls the phase of the external laser pulse to the second preset phase. , recorded as operation At this point, the remaining atomic sequence The energy level states are Alice performs the following four unitary operations on the atomic sequence. Encode: , , , , recorded as , , , The encoded atomic sequence is denoted as ; The above eight operations are the coding operations performed by Alice. U Alice ; Step 6: Alice processes the atomic sequence carrying the information. Perform Hadamard door operations; that is: , ; Step 7: Alice analyzes the atomic sequence The measurement was performed, and the results were announced to Bob; Bob measured the atoms. Based on the measurement results, the coding operations performed by Alice can be inferred. U Alice Subsequently, Bob compared Alice's atomic sequence. Decode to obtain the encoding operation U Alice The corresponding encoding information.

2. The quantum teleportation method based on atoms and photons as described in claim 1, characterized in that, In step 1, the atomic sequence and atomic sequence The fabrication process involves the following steps: A superposition of "Schrödinger cat" states is generated using continuous laser pulses from a Raman beam; the atomic energy level states are manipulated through quantum mechanical interference between local wave packets; by controlling the duration and phase of the laser pulses acting on the qubits, a phase change of π / 2 radians is achieved in the atomic system. This pulse changes the internal state of the atom from... Rotate to and The superposition of states causes the wave packet to split in the location space.

3. The quantum teleportation method based on atom-photon entanglement as described in claim 1, characterized in that, In step 2, the time-division multiplexing process is as follows: Step 1, Amplitude Modulation: Reference light time slot: AM fully open, outputting a strong coherent light pulse with a power much higher than the signal light to ensure interference contrast; Signal optical time slot: AM attenuation, outputting weakly coherent optical pulses; Step 2, Polarization Modulation: The pulse sequence generated by amplitude modulation is subjected to PM modulation to generate signal light pulses. The reference light time slot and the signal light time slot alternate at time intervals. T It is distributed into the channel and transmitted to Bob's end.

4. The quantum teleportation method based on atom-photon entanglement as described in claim 1, characterized in that, In step 5: 。 5. The quantum teleportation method based on atom-photon entanglement as described in claim 1, characterized in that, In step 5, the first preset phase Pick Second preset phase Pick .

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