Journals > > Topics > Quantum Optics
Quantum Optics|104 Article(s)
Quantum Classifier Based on Compact Encoding and Polynomial Kernel
Ruihong Jia, Guang Yang, Min Nie, Yuanhua Liu, and Meiling Zhang
Kernel method has a wide range of applications in machine learning. The combination of quantum computing and kernel method can effectively solve the problem of increasing computational costs in classical kernel method when the feature space becomes larger. Researches show that the minimized quantum circuits based on kernel method can be reliably executed on noisy intermediate-scale quantum devices. Some classifiers based on the quantum kernel method that have been proposed so far still have certain defects in terms of fully mapping data and circuit architecture. Therefore, we propose a compact quantum classifier based on polynomial kernel functions. First, a polynomial kernel function is introduced to increase the classification iteration rate of nonlinear data, thereby improve the classification efficiency. On this basis, a compact amplitude encoding is further proposed to encode the data labels corresponding to the quantum state. Compared with the existing quantum kernel method classifier, the number of coding bits of the quantum circuit of the proposed model can be reduced from 5 qubits to 3 qubits, and the two-qubit measurement in the existing method is simplified to a single-qubit measurement in the proposed model. In addition, the model achieves the optimal variance of the quantum circuit parameters in the measurement stage, which can effectively save computing resource overhead. Experimental simulations show that the expected value in the proposed classifier model is closer to the theoretical one, and higher classification accuracy is obtained. At the same time, the model has a low degree of entanglement, which effectively reduces the overhead of the entire preparation work. Kernel method has a wide range of applications in machine learning. The combination of quantum computing and kernel method can effectively solve the problem of increasing computational costs in classical kernel method when the feature space becomes larger. Researches show that the minimized quantum circuits based on kernel method can be reliably executed on noisy intermediate-scale quantum devices. Some classifiers based on the quantum kernel method that have been proposed so far still have certain defects in terms of fully mapping data and circuit architecture. Therefore, we propose a compact quantum classifier based on polynomial kernel functions. First, a polynomial kernel function is introduced to increase the classification iteration rate of nonlinear data, thereby improve the classification efficiency. On this basis, a compact amplitude encoding is further proposed to encode the data labels corresponding to the quantum state. Compared with the existing quantum kernel method classifier, the number of coding bits of the quantum circuit of the proposed model can be reduced from 5 qubits to 3 qubits, and the two-qubit measurement in the existing method is simplified to a single-qubit measurement in the proposed model. In addition, the model achieves the optimal variance of the quantum circuit parameters in the measurement stage, which can effectively save computing resource overhead. Experimental simulations show that the expected value in the proposed classifier model is closer to the theoretical one, and higher classification accuracy is obtained. At the same time, the model has a low degree of entanglement, which effectively reduces the overhead of the entire preparation work.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0927002 (2024)
Quantum Walk Wave-Particle Coherent Superposition
Shuo Li, and Rong Zhang
Evolution process and properties of wave-particle quantum walk (QW) are studied by theoretical calculation and quantum simulator's simulation. Quantum control can contribute to the realization of QWs in quantum wave-particle superposition state with a relative phase between walkers. The post-selection operation is used to realize the continuous transitions of QW from the state of waves with multi-path coherence to the state of particles without coherence in two different ways: coherence and mixing. Due to quantum interference, there are essential differences between coherence and mixing, and their specific features are characterized by position variance. We also demonstrate the coherent wave-particle QWs in the real quantum simulator. When the walker is in the wave-particle coherent state, two completely different properties can be observed simultaneously through one measurement. By adjusting the relative phase in the wave-particle coherent state, the diffusion rate of the walker can be controlled. Evolution process and properties of wave-particle quantum walk (QW) are studied by theoretical calculation and quantum simulator's simulation. Quantum control can contribute to the realization of QWs in quantum wave-particle superposition state with a relative phase between walkers. The post-selection operation is used to realize the continuous transitions of QW from the state of waves with multi-path coherence to the state of particles without coherence in two different ways: coherence and mixing. Due to quantum interference, there are essential differences between coherence and mixing, and their specific features are characterized by position variance. We also demonstrate the coherent wave-particle QWs in the real quantum simulator. When the walker is in the wave-particle coherent state, two completely different properties can be observed simultaneously through one measurement. By adjusting the relative phase in the wave-particle coherent state, the diffusion rate of the walker can be controlled.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0527002 (2024)
Fast Post-processing Method for Practical Quantum Random Number Generators Based on Spontaneous Emission Amplification
Qixia Tong, Yingying Hu, Deyong He, and Zhengfu Han
In practical applications of high-speed quantum random number generators, using Toeplitz matrices as a post-processing method to extract the randomness of quantum random numbers has become a major technology roadmap. However, Toeplitz matrices are more suitable for hardware calculations than for software calculations and typically require that specialized field programmable gate array (FPGA) circuits be constructed for fast calculations. Based on the quantum random generator of spontaneous emission amplification (ASE), a fast post-processing method based on a simple hash function is proposed. The time complexity of this method is only O(N), which is less than O(NlogN) of a Toeplitz matrix, and compared with another commonly used post-processing method, least significant bit (LSB) post-processing has higher efficiency in random number extraction. The random number calculated by the proposed post-processing method in the experiment passes the randomness test of the national institute of standards and technology (NIST) in the United States. In practical applications of high-speed quantum random number generators, using Toeplitz matrices as a post-processing method to extract the randomness of quantum random numbers has become a major technology roadmap. However, Toeplitz matrices are more suitable for hardware calculations than for software calculations and typically require that specialized field programmable gate array (FPGA) circuits be constructed for fast calculations. Based on the quantum random generator of spontaneous emission amplification (ASE), a fast post-processing method based on a simple hash function is proposed. The time complexity of this method is only O(N), which is less than O(NlogN) of a Toeplitz matrix, and compared with another commonly used post-processing method, least significant bit (LSB) post-processing has higher efficiency in random number extraction. The random number calculated by the proposed post-processing method in the experiment passes the randomness test of the national institute of standards and technology (NIST) in the United States.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2024
- Vol. 61, Issue 5, 0527001 (2024)
Enhancing Minimum-Consumption Discrimination of Two-Qubit Quantum States via Entangling Measurements (Invited)
Boxuan Tian, Zhibo Hou, and Guoyong Xiang
Reducing the average number of copies consumed in quantum state discrimination under a given error rate is referred to as minimum-consumption quantum state discrimination. Minimum-consumption quantum state discrimination allows the saved resources to be utilized for subsequent quantum tasks, and it holds significant practical value in tasks such as quantum cryptography. In this paper, we investigate minimum-consumption quantum state discrimination of two-qubit quantum states. The theoretical results indicate that even when two-qubit quantum states only possess classical correlations and no quantum entanglement, entangled measurements still far outperform the effects of performing local measurements on the two qubits individually. Experimental results confirm that when the error rate requirement is low enough, the average number of copies consumed by entangled measurement device is only one-twelfth of that consumed by local measurements, while still meeting the error rate requirement. Our research results highlight the role of entangled measurements in minimum-consuption quantum state discrimination, demonstrating the importance of entanglement in quantum measurements. Reducing the average number of copies consumed in quantum state discrimination under a given error rate is referred to as minimum-consumption quantum state discrimination. Minimum-consumption quantum state discrimination allows the saved resources to be utilized for subsequent quantum tasks, and it holds significant practical value in tasks such as quantum cryptography. In this paper, we investigate minimum-consumption quantum state discrimination of two-qubit quantum states. The theoretical results indicate that even when two-qubit quantum states only possess classical correlations and no quantum entanglement, entangled measurements still far outperform the effects of performing local measurements on the two qubits individually. Experimental results confirm that when the error rate requirement is low enough, the average number of copies consumed by entangled measurement device is only one-twelfth of that consumed by local measurements, while still meeting the error rate requirement. Our research results highlight the role of entangled measurements in minimum-consuption quantum state discrimination, demonstrating the importance of entanglement in quantum measurements.
Laser & Optoelectronics Progress
- Publication Date: Feb. 10, 2024
- Vol. 61, Issue 3, 0327001 (2024)
Advances in Entanglement-Based Remote State Preparation (Invited)
Xiaolong Su, Dongmei Han, Na Wang, and Meihong Wang
Remote state preparation stands as a crucial protocol for transmitting quantum states, facilitating the remote preparation and manipulation of quantum states through distributed quantum entanglement. In recent times, notable progress has been achieved in remote state preparation, encompassing the remote preparation of single qubits, continuous-variable qubits, squeezed states, non-Gaussian states, and optical cat states. This paper provides a concise overview of the principles behind remote state preparation, highlighting the research advancements and developmental trends in both discrete and continuous variable systems. Remote state preparation stands as a crucial protocol for transmitting quantum states, facilitating the remote preparation and manipulation of quantum states through distributed quantum entanglement. In recent times, notable progress has been achieved in remote state preparation, encompassing the remote preparation of single qubits, continuous-variable qubits, squeezed states, non-Gaussian states, and optical cat states. This paper provides a concise overview of the principles behind remote state preparation, highlighting the research advancements and developmental trends in both discrete and continuous variable systems.
Laser & Optoelectronics Progress
- Publication Date: Jan. 10, 2024
- Vol. 61, Issue 1, 0127001 (2024)
Nuclear-Magnetic-Resonance-Based Physical Realization of Quantum Toffoli Gate
Yonggang Peng
The three-qubit Toffoli gate is equivalent to the combination of two two-qubit controlled NOT gates and three two-qubit controlled phase-shift gates. The controlled NOT and phase-shift gates respectively comprise a combination of nuclear-magnetic-resonance pulse sequences and a free development operator of two nuclear spins with time. According to the order in which the controlled NOT and phase-shift gates act on the nuclear spin system, the nuclear-magnetic-resonance-based physical realization of a quantum Toffoli gate is achieved. The time-dependent Schr?dinger equation is numerically solved by the Suzuki formula to confirm the correctness and feasibility of the realization of the quantum Toffoli gate based on nuclear magnetic resonance. The three-qubit Toffoli gate is equivalent to the combination of two two-qubit controlled NOT gates and three two-qubit controlled phase-shift gates. The controlled NOT and phase-shift gates respectively comprise a combination of nuclear-magnetic-resonance pulse sequences and a free development operator of two nuclear spins with time. According to the order in which the controlled NOT and phase-shift gates act on the nuclear spin system, the nuclear-magnetic-resonance-based physical realization of a quantum Toffoli gate is achieved. The time-dependent Schr?dinger equation is numerically solved by the Suzuki formula to confirm the correctness and feasibility of the realization of the quantum Toffoli gate based on nuclear magnetic resonance.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2023
- Vol. 60, Issue 7, 0727002 (2023)
Routing Protocol for Quantum Multicast Networks Based on Hyperentangled Relays
Lei Xing, Guang Yang, Min Nie, Yuanhua Liu, and Meiling Zhang
In this study, a multicast routing protocol for hyperentangled relay quantum networks is proposed to solve the problem of path selection, the establishment of multicast communication in quantum networks, and improve the communication performance of quantum multicast networks. The networks use a diamond structure to ensure the fidelity of quantum clones in multicast communication. The single-photon polarization-space mode quantum state was cloned using a quantum cloning machine, and an optimization algorithm based on the Steiner tree was used to generate a multicast tree by considering the number of hyperentanglement resources, hops, and fidelity of the cloned state. A multicast quantum channel between remote users was established based on simultaneous hyperentanglement swapping after selecting the routing. Theoretical analysis and simulation results show that in multicast communication of an increase in destination nodes, the routing protocol based on a hyperentangled relay can obtain a multicast tree with high fidelity. When the number of relay nodes increases, the delay in establishing a quantum channel using simultaneous hyperentangled swapping is lower than that of traditional sequential entangled swapping, and the transmission rate of a quantum state is faster. Therefore, the routing protocol of quantum multicast networks based on hyperentangled relays has the advantages of high fidelity and low-multicast communication delay. In this study, a multicast routing protocol for hyperentangled relay quantum networks is proposed to solve the problem of path selection, the establishment of multicast communication in quantum networks, and improve the communication performance of quantum multicast networks. The networks use a diamond structure to ensure the fidelity of quantum clones in multicast communication. The single-photon polarization-space mode quantum state was cloned using a quantum cloning machine, and an optimization algorithm based on the Steiner tree was used to generate a multicast tree by considering the number of hyperentanglement resources, hops, and fidelity of the cloned state. A multicast quantum channel between remote users was established based on simultaneous hyperentanglement swapping after selecting the routing. Theoretical analysis and simulation results show that in multicast communication of an increase in destination nodes, the routing protocol based on a hyperentangled relay can obtain a multicast tree with high fidelity. When the number of relay nodes increases, the delay in establishing a quantum channel using simultaneous hyperentangled swapping is lower than that of traditional sequential entangled swapping, and the transmission rate of a quantum state is faster. Therefore, the routing protocol of quantum multicast networks based on hyperentangled relays has the advantages of high fidelity and low-multicast communication delay.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2023
- Vol. 60, Issue 7, 0727001 (2023)
Imaging Scheme Based on Spatially Correlated Quantum Signals
Zhaoheng Ren, Qiang Miao, Dewei Wu, Tianli Wei, Luhan Zhao, and Yongfei Liu
The unique spatial correlation properties of quantum entangled signals can overcome technical barriers, such as those presented by the distance and accuracy, encountered by classical imaging approaches. Therefore, herein, the principle of “ghost imaging” of entangled signals is summarized and is then introduced in the field of navigation. Accordingly, an imaging scheme of hybrid entangled quantum signals generated using a cavity-electric photoelectric light converter is proposed. In contrast to the traditional imaging method, herein, based on theoretical analyses and simulations, the spatial correlation characteristics of entangled microwave signals are completely utilized, and the images that cannot be observed by classical methods are generated in a “nonlocal” manner; correspondingly, the signal-to-noise ratio is higher than that of the classical scheme when weak signals are detected. That is, the imaging quality is better than that of the classical scheme, and it has the ability to resist atmospheric turbulence disturbances unlike the classical scheme. The unique spatial correlation properties of quantum entangled signals can overcome technical barriers, such as those presented by the distance and accuracy, encountered by classical imaging approaches. Therefore, herein, the principle of “ghost imaging” of entangled signals is summarized and is then introduced in the field of navigation. Accordingly, an imaging scheme of hybrid entangled quantum signals generated using a cavity-electric photoelectric light converter is proposed. In contrast to the traditional imaging method, herein, based on theoretical analyses and simulations, the spatial correlation characteristics of entangled microwave signals are completely utilized, and the images that cannot be observed by classical methods are generated in a “nonlocal” manner; correspondingly, the signal-to-noise ratio is higher than that of the classical scheme when weak signals are detected. That is, the imaging quality is better than that of the classical scheme, and it has the ability to resist atmospheric turbulence disturbances unlike the classical scheme.
Laser & Optoelectronics Progress
- Publication Date: Mar. 25, 2023
- Vol. 60, Issue 6, 0627001 (2023)
Improving Satellite Time Service Accuracy Based on Microwave-Optical Wave Entangled Signals
Yongfei Liu, Chunyan Yang, Luhan Zhao, Tianli Wei, Dewei Wu, and Zhaoheng Ren
The satellite time service technology is limited by the measurement accuracy of the classical radio signal, and the time service accuracy can only reach the ns level. In this paper, a satellite time service scheme based on microwave-optical wave-entangled signals is proposed. The advantages of long-distance transmission of microwave signals and single-photon detection of optical wave signals are effectively combined using a cavity electro-opto-mechanical converter. The phase difference is calculated using a phase-conjugating processor to obtain accurate time-difference information. Through theoretical analysis and simulations, it is demonstrated that even if the quantum signal is in low entanglement, the proposed scheme can improve the satellite time service accuracy to the ps level. The satellite time service technology is limited by the measurement accuracy of the classical radio signal, and the time service accuracy can only reach the ns level. In this paper, a satellite time service scheme based on microwave-optical wave-entangled signals is proposed. The advantages of long-distance transmission of microwave signals and single-photon detection of optical wave signals are effectively combined using a cavity electro-opto-mechanical converter. The phase difference is calculated using a phase-conjugating processor to obtain accurate time-difference information. Through theoretical analysis and simulations, it is demonstrated that even if the quantum signal is in low entanglement, the proposed scheme can improve the satellite time service accuracy to the ps level.
Laser & Optoelectronics Progress
- Publication Date: Mar. 10, 2023
- Vol. 60, Issue 5, 0527001 (2023)
Effect of Snowfall on Communication Performance of Satellite Ground Quantum Link
Changchun Xue, Min Nie, Guang Yang, Meiling Zhang, Aijing Sun, and Changxing Pei
Quantum satellite communication is an important part of global quantum secure communication network. In order to study the effect of snowfall on quantum satellite communication performance, first, based on the Gamma spectrum distribution function of snow particles and Mie scattering theory, the energy attenuation model of light quantum in snowfall environment is established. Then the relationship between the parameters such as snowfall intensity and the fidelity of the satellite-ground link, the channel establishment rate and the channel entanglement is studied, and the numerical simulation is carried out. Finally, in order to accurately simulate the impact of snow interference on the communication performance of satellite-ground links, a weighted noise channel model is introduced, and the impact of snow on the weighted noise channel capacity is analyzed. The results show that the snowfall intensity has a significant effect on the quantum energy and fidelity of light. When the transmission distance is 4.1 km and the snowfall intensity increases from 2.82 mm/d to 8.71 mm/d, the entanglement decreases from 0.738 to 0.206. When the snowfall intensity increases from 3.75 mm/d to 8.25 mm/d, the channel establishment rate decreases from 16.84 pair/s to 7.76 pair/s. When the transmission distance is 2.5 km and the snowfall intensity increases from 4.0 mm/d to 8.5 mm/d, the weighted noise channel capacity decreases from 0.6207 to 0.3547. Therefore, the impact of snowfall on quantum satellite communication system cannot be ignored, and corresponding adjustment strategies should be taken to ensure the reliability and effectiveness of communication according to the snowfall level. Quantum satellite communication is an important part of global quantum secure communication network. In order to study the effect of snowfall on quantum satellite communication performance, first, based on the Gamma spectrum distribution function of snow particles and Mie scattering theory, the energy attenuation model of light quantum in snowfall environment is established. Then the relationship between the parameters such as snowfall intensity and the fidelity of the satellite-ground link, the channel establishment rate and the channel entanglement is studied, and the numerical simulation is carried out. Finally, in order to accurately simulate the impact of snow interference on the communication performance of satellite-ground links, a weighted noise channel model is introduced, and the impact of snow on the weighted noise channel capacity is analyzed. The results show that the snowfall intensity has a significant effect on the quantum energy and fidelity of light. When the transmission distance is 4.1 km and the snowfall intensity increases from 2.82 mm/d to 8.71 mm/d, the entanglement decreases from 0.738 to 0.206. When the snowfall intensity increases from 3.75 mm/d to 8.25 mm/d, the channel establishment rate decreases from 16.84 pair/s to 7.76 pair/s. When the transmission distance is 2.5 km and the snowfall intensity increases from 4.0 mm/d to 8.5 mm/d, the weighted noise channel capacity decreases from 0.6207 to 0.3547. Therefore, the impact of snowfall on quantum satellite communication system cannot be ignored, and corresponding adjustment strategies should be taken to ensure the reliability and effectiveness of communication according to the snowfall level.
Laser & Optoelectronics Progress
- Publication Date: Dec. 10, 2023
- Vol. 60, Issue 23, 2327001 (2023)
Topics
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20