To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z_(2~n)), which could re...To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z_(2~n)), which could realize large-scale QFT using an arbitrary-scale quantum register. By developing a feasible method to realize the control quantum gate Rk, we experimentally realize the 2-bit semiclassical QFT over Z_(2~3) on IBM's quantum cloud computer, which shows the feasibility of the method. Then, we compare the actual performance of 2-bit semiclassical QFT with standard QFT in the experiments.The squared statistical overlap experimental data shows that the fidelity of 2-bit semiclassical QFT is higher than that of standard QFT, which is mainly due to fewer two-qubit gates in the semiclassical QFT. Furthermore, based on the proposed method, N = 15 is successfully factorized by implementing Shor's algorithm.展开更多
High-fidelity two-qubit gates are essential for the realization of large-scale quantum computation and simulation.Tunable coupler design is used to reduce the problem of parasitic coupling and frequency crowding in ma...High-fidelity two-qubit gates are essential for the realization of large-scale quantum computation and simulation.Tunable coupler design is used to reduce the problem of parasitic coupling and frequency crowding in manyqubit systems and thus thought to be advantageous. Here we design an extensible 5-qubit system in which center transmon qubit can couple to every four near-neighboring qubits via a capacitive tunable coupler and experimentally demonstrate high-fidelity controlled-phase(CZ) gate by manipulating central qubit and one nearneighboring qubit. Speckle purity benchmarking and cross entropy benchmarking are used to assess the purity fidelity and the fidelity of the CZ gate. The average purity fidelity of the CZ gate is 99.69±0.04% and the average fidelity of the CZ gate is 99.65±0.04%, which means that the control error is about 0.04%. Our work is helpful for resolving many challenges in implementation of large-scale quantum systems.展开更多
The development of high-fidelity two-qubit quantum gates is essential for digital quantum computing.Here,we propose and realize an all-microwave parametric controlled-Z(CZ)gates by coupling strength modulation in a su...The development of high-fidelity two-qubit quantum gates is essential for digital quantum computing.Here,we propose and realize an all-microwave parametric controlled-Z(CZ)gates by coupling strength modulation in a superconducting Transmon qubit system with tunable couplers.After optimizing the design of the tunable coupler together with the control pulse numerically,we experimentally realized a 100 ns CZ gate with high fidelity of 99.38%±0.34%and the control error being 0.1%.We note that our CZ gates are not affected by pulse distortion and do not need pulse correction,providing a solution for the real-time pulse generation in a dynamic quantum feedback circuit.With the expectation of utilizing our all-microwave control scheme to reduce the number of control lines through frequency multiplexing in the future,our scheme draws a blueprint for the high-integrable quantum hardware design.展开更多
We present two efficient quantum adiabatic algorithms for Bernstein–Vazirani problem and Simon’s problem.We show that the time complexities of the algorithms for Bernstein–Vazirani problem and Simon’s problem are ...We present two efficient quantum adiabatic algorithms for Bernstein–Vazirani problem and Simon’s problem.We show that the time complexities of the algorithms for Bernstein–Vazirani problem and Simon’s problem are O(1)and O(n),respectively,which are the same complexities as the corresponding algorithms in quantum circuit model.In these two algorithms,the adiabatic Hamiltonians are realized by unitary interpolation instead of standard linear interpolation.Comparing with the adiabatic algorithms using linear interpolation,the energy gaps of our algorithms keep constant.Therefore,the complexities are much easier to analyze using this method.展开更多
Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Altho...Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Although it has seen a major boost in the last decade,we are still a long way from reaching the maturity of a full-fledged quantum computer.That said,we will be in the noisy-intermediate scale quantum(NISQ)era for a long time,working on dozens or even thousands of qubits quantum computing systems.An outstanding challenge,then,is to come up with an application that can reliably carry out a nontrivial task of interest on the near-term quantum devices with non-negligible quantum noise.To address this challenge,several near-term quantum computing techniques,including variational quantum algorithms,error mitigation,quantum circuit compilation and benchmarking protocols,have been proposed to characterize and mitigate errors,and to implement algorithms with a certain resistance to noise,so as to enhance the capabilities of near-term quantum devices and explore the boundaries of their ability to realize useful applications.Besides,the development of near-term quantum devices is inseparable from the efficient classical sim-ulation,which plays a vital role in quantum algorithm design and verification,error-tolerant verification and other applications.This review will provide a thorough introduction of these near-term quantum computing techniques,report on their progress,and finally discuss the future prospect of these techniques,which we hope will motivate researchers to undertake additional studies in this field.展开更多
Qubit measurement is generally the most error-prone operation that degrades the performance of near-term quantum devices,and the exponential decay of readout fidelity severely impedes the development of large-scale qu...Qubit measurement is generally the most error-prone operation that degrades the performance of near-term quantum devices,and the exponential decay of readout fidelity severely impedes the development of large-scale quantum information processing.Given these disadvantages, we present a quantum state readout method, named compression readout, that naturally avoids large multi-qubit measurement errors by compressing the quantum state into a single qubit for measurement. Our method generally outperforms direct measurements in terms of accuracy, and the advantage grows with the system size. Moreover, because only one-qubit measurements are performed, our method requires solely a fine readout calibration on one qubit and is free of correlated measurement error, which drastically diminishes the demand for device calibration. These advantages suggest that our method can immediately boost the readout performance of near-term quantum devices and will greatly benefit the development of large-scale quantum computing.展开更多
Deep learning has been shown to be able to recognize data patterns better than humans in specific circumstances or contexts.In parallel,quantum computing has demonstrated to be able to output complex wave functions wi...Deep learning has been shown to be able to recognize data patterns better than humans in specific circumstances or contexts.In parallel,quantum computing has demonstrated to be able to output complex wave functions with a few number of gate operations,which could generate distributions that are hard for a classical computer to produce.Here we propose a hybrid quantum-classical convolutional neural network(QCCNN),inspired by convolutional neural networks(CNNs)but adapted to quantum computing to enhance the feature mapping process.QCCNN is friendly to currently noisy intermediate-scale quantum computers,in terms of both number of qubits as well as circuit’s depths,while retaining important features of classical CNN,such as nonlinearity and scalability.We also present a framework to automatically compute the gradients of hybrid quantum-classical loss functions which could be directly applied to other hybrid quantum-classical algorithms.We demonstrate the potential of this architecture by applying it to a Tetris dataset,and show that QCCNN can accomplish classification tasks with learning accuracy surpassing that of classical CNN with the same structure.展开更多
Quantum computing has undergone rapid development in recent years. Owing to limitations on scalability, personal quantum computers still seem slightly unrealistic in the near future. The first practical quantum comput...Quantum computing has undergone rapid development in recent years. Owing to limitations on scalability, personal quantum computers still seem slightly unrealistic in the near future. The first practical quantum computer for ordinary users is likely to be on the cloud. However, the adoption of cloud computing is possible only if security is ensured. Homomorphic encryption is a cryptographic protocol that allows computation to be performed on encrypted data without decrypting them, so it is well suited to cloud computing. Here, we first applied homomorphic encryption on IBM's cloud quantum computer platform. In our experiments, we successfully implemented a quantum algorithm for linear equations while protecting our privacy. This demonstration opens a feasible path to the next stage of development of cloud quantum information technology.展开更多
Since the pillars of quantum theory were established, it was already noted that quantum physics may allow certain correlations defying any local realistic picture of nature, as first recognized by Einstein,Podolsky an...Since the pillars of quantum theory were established, it was already noted that quantum physics may allow certain correlations defying any local realistic picture of nature, as first recognized by Einstein,Podolsky and Rosen. These quantum correlations, now termed quantum nonlocality and tested by violation of Bell's inequality that consists of statistical correlations fulfilling local realism, have found loophole-free experimental confirmation. A more striking way to demonstrate the conflict exists, and can be extended to the multipartite scenario. Here we report experimental confirmation of such a striking way, the multipartite generalized Hardy's paradoxes, in which no inequality is used and the conflict is stronger than that within just two parties. The paradoxes we consider here belong to a general framework [S.-H. Jiang et al., Phys. Rev. Lett. 120(2018) 050403], including previously known multipartite extensions of Hardy's original paradox as special cases. The conflict shown here is stronger than in previous multipartite Hardy's paradox. Thus, the demonstration of Hardy-typed quantum nonlocality becomes sharper than ever.展开更多
Quantum algorithms can be used to efficiently solve certain classically intractable problems by exploiting quantum parallelism.However, the effectiveness of quantum entanglement in quantum computing remains a question...Quantum algorithms can be used to efficiently solve certain classically intractable problems by exploiting quantum parallelism.However, the effectiveness of quantum entanglement in quantum computing remains a question of debate. This study presents a new quantum algorithm that shows entanglement could provide advantages over both classical algorithms and quantum algorithms without entanglement. Experiments are implemented to demonstrate the proposed algorithm using superconducting qubits.Results show the viability of the algorithm and suggest that entanglement is essential in obtaining quantum speedup for certain problems in quantum computing. The study provides reliable and clear guidance for developing useful quantum algorithms.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CB338002)the National Natural Science Foundation of China(Grant No.61502526)
文摘To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z_(2~n)), which could realize large-scale QFT using an arbitrary-scale quantum register. By developing a feasible method to realize the control quantum gate Rk, we experimentally realize the 2-bit semiclassical QFT over Z_(2~3) on IBM's quantum cloud computer, which shows the feasibility of the method. Then, we compare the actual performance of 2-bit semiclassical QFT with standard QFT in the experiments.The squared statistical overlap experimental data shows that the fidelity of 2-bit semiclassical QFT is higher than that of standard QFT, which is mainly due to fewer two-qubit gates in the semiclassical QFT. Furthermore, based on the proposed method, N = 15 is successfully factorized by implementing Shor's algorithm.
基金the National Key R&D Program of China(Grant No.2017YFA0304300)the Chinese Academy of Sciences+6 种基金Anhui Initiative in Quantum Information TechnologiesTechnology Committee of Shanghai Municipalitythe National Natural Science Foundation of China(Grants Nos.11905217,11774326,and 11905294)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the Natural Science Foundation of Shanghai(Grant No.19ZR1462700)the Key-Area Research and Development Program of Guangdong Provice(Grant No.2020B0303030001)the Youth Talent Lifting Project(Grant No.2020-JCJQ-QT-030)。
文摘High-fidelity two-qubit gates are essential for the realization of large-scale quantum computation and simulation.Tunable coupler design is used to reduce the problem of parasitic coupling and frequency crowding in manyqubit systems and thus thought to be advantageous. Here we design an extensible 5-qubit system in which center transmon qubit can couple to every four near-neighboring qubits via a capacitive tunable coupler and experimentally demonstrate high-fidelity controlled-phase(CZ) gate by manipulating central qubit and one nearneighboring qubit. Speckle purity benchmarking and cross entropy benchmarking are used to assess the purity fidelity and the fidelity of the CZ gate. The average purity fidelity of the CZ gate is 99.69±0.04% and the average fidelity of the CZ gate is 99.65±0.04%, which means that the control error is about 0.04%. Our work is helpful for resolving many challenges in implementation of large-scale quantum systems.
基金the USTC Center for Micro-and Nanoscale Research and Fabrication for supporting the sample fabricationQuantum CTek Co.,Ltd.for supporting the fabrication and the maintenance of room-temperature electronics+7 种基金supported by the National Key R&D Program of China(Grant No.2017YFA0304300)the Chinese Academy of Sciencesthe Anhui Initiative in Quantum Information Technologiesthe Technology Committee of Shanghai Municipalitythe National Natural Science Foundation of China(Grants No.11905217 and 11905294)the Natural Science Foundation of Shanghai(Grant No.19ZR1462700)he Key-Area Research and Development Program of Guangdong Province(Grant No.2020B0303030001)the China Postdoctoral Science Foundation。
文摘The development of high-fidelity two-qubit quantum gates is essential for digital quantum computing.Here,we propose and realize an all-microwave parametric controlled-Z(CZ)gates by coupling strength modulation in a superconducting Transmon qubit system with tunable couplers.After optimizing the design of the tunable coupler together with the control pulse numerically,we experimentally realized a 100 ns CZ gate with high fidelity of 99.38%±0.34%and the control error being 0.1%.We note that our CZ gates are not affected by pulse distortion and do not need pulse correction,providing a solution for the real-time pulse generation in a dynamic quantum feedback circuit.With the expectation of utilizing our all-microwave control scheme to reduce the number of control lines through frequency multiplexing in the future,our scheme draws a blueprint for the high-integrable quantum hardware design.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504430,11805279,61501514,and 61502526)
文摘We present two efficient quantum adiabatic algorithms for Bernstein–Vazirani problem and Simon’s problem.We show that the time complexities of the algorithms for Bernstein–Vazirani problem and Simon’s problem are O(1)and O(n),respectively,which are the same complexities as the corresponding algorithms in quantum circuit model.In these two algorithms,the adiabatic Hamiltonians are realized by unitary interpolation instead of standard linear interpolation.Comparing with the adiabatic algorithms using linear interpolation,the energy gaps of our algorithms keep constant.Therefore,the complexities are much easier to analyze using this method.
基金support from the Youth Talent Lifting Project(Grant No.2020-JCJQ-QT-030)the National Natural Science Foundation of China(Grant Nos.11905294,and 12274464)+7 种基金the China Postdoctoral Science Foundation,and the Open Research Fund from State Key Laboratory of High Performance Computing of China(Grant No.201901-01)support from the National Natural Science Foundation of China(Grant Nos.11805279,12074117,61833010,and 12061131011)support from the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the National Natural Science Foundation of China(Grant Nos.61832003,61872334,and 61801459)the National Natural Science Foundation of China(Grant No.12005015)the National Natural Science Foundation of China(Grant Nos.11974205,and 11774197)the National Key Research and Development Program of China(Grant No.2017YFA0303700)the Key Research and Development Program of Guangdong Province(Grant No.2018B030325002).
文摘Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Although it has seen a major boost in the last decade,we are still a long way from reaching the maturity of a full-fledged quantum computer.That said,we will be in the noisy-intermediate scale quantum(NISQ)era for a long time,working on dozens or even thousands of qubits quantum computing systems.An outstanding challenge,then,is to come up with an application that can reliably carry out a nontrivial task of interest on the near-term quantum devices with non-negligible quantum noise.To address this challenge,several near-term quantum computing techniques,including variational quantum algorithms,error mitigation,quantum circuit compilation and benchmarking protocols,have been proposed to characterize and mitigate errors,and to implement algorithms with a certain resistance to noise,so as to enhance the capabilities of near-term quantum devices and explore the boundaries of their ability to realize useful applications.Besides,the development of near-term quantum devices is inseparable from the efficient classical sim-ulation,which plays a vital role in quantum algorithm design and verification,error-tolerant verification and other applications.This review will provide a thorough introduction of these near-term quantum computing techniques,report on their progress,and finally discuss the future prospect of these techniques,which we hope will motivate researchers to undertake additional studies in this field.
基金supported by Innovation Program for Quantum Science and Technology (2021ZD0300200)Shanghai Municipal Science and Technology Major Project (2019SHZDZX01)+13 种基金Special funds from Jinan Science and Technology Bureau and Jinan High Tech Zone Management Committeethe Chinese Academy of Sciences (CAS)Anhui Initiative in Quantum Information TechnologiesTechnology Committee of Shanghai MunicipalityNatural Science Foundation of Shandong Province (ZR202209080019)Key-Area Research and Development Program of Guangdong Provice (2020B0303030001)supported in part by the Japanese MEXT Quantum Leap Flagship Program (MEXT Q-LEAP,JPMXS0118069605)the support from the Youth Talent Lifting Project (2020-JCJQ-QT-030)the National Natural Science Foundation of China (12274464,and 11905294)China Postdoctoral Science Foundationthe Open Research Fund from State Key Laboratory of High Performance Computing of China (201901-01)supported by Shanghai Rising-Star Program (23QA1410000)the Youth Innovation Promotion Association of CAS (2022460)the support from THE XPLORER PRIZE。
基金supported by the Youth Talent Lifting Project(Grant No.2020-JCJQ-QT-030)National Natural Science Foundation of China(Grants Nos.11905294,and 12274464)+1 种基金China Postdoctoral Science FoundationOpen Research Fund from State Key Laboratory of High Performance Computing of China(Grant No.201901-01)。
文摘Qubit measurement is generally the most error-prone operation that degrades the performance of near-term quantum devices,and the exponential decay of readout fidelity severely impedes the development of large-scale quantum information processing.Given these disadvantages, we present a quantum state readout method, named compression readout, that naturally avoids large multi-qubit measurement errors by compressing the quantum state into a single qubit for measurement. Our method generally outperforms direct measurements in terms of accuracy, and the advantage grows with the system size. Moreover, because only one-qubit measurements are performed, our method requires solely a fine readout calibration on one qubit and is free of correlated measurement error, which drastically diminishes the demand for device calibration. These advantages suggest that our method can immediately boost the readout performance of near-term quantum devices and will greatly benefit the development of large-scale quantum computing.
基金the National Key R&D Program of China(2017YFA0304300),the Chinese Academy of Sciences,Anhui Initiative in Quantum Information Technologies,Technology Committee of Shanghai Municipality,National Natural Science Foundation of China(11905217,11774326,and 11905294)‘Shang-hai Municipal Science and Technology Major Project(2019SHZDZX01)’Natural Science Foundation of Shanghai(19ZR1462700)‘Key-Area Research and Development Program of Guangdong Province(2020B0303030001)’the Youth Talent Lifting Project(2020-JCJQ-QT-030)。
基金support from the National Natural Science Foundation of China(Grant No.11805279).He-Liang Huang acknowledges support from the Youth Talent Lifting Project(Grant No.2020-JCJQ-QT-030),the National Natural Science Foundation of China(Grant No.11905294),the China Postdoctoral Science Foundation,and the Open Research Fund from State Key Laboratory of High Performance Computing of China(Grant No.201901-01).
文摘Deep learning has been shown to be able to recognize data patterns better than humans in specific circumstances or contexts.In parallel,quantum computing has demonstrated to be able to output complex wave functions with a few number of gate operations,which could generate distributions that are hard for a classical computer to produce.Here we propose a hybrid quantum-classical convolutional neural network(QCCNN),inspired by convolutional neural networks(CNNs)but adapted to quantum computing to enhance the feature mapping process.QCCNN is friendly to currently noisy intermediate-scale quantum computers,in terms of both number of qubits as well as circuit’s depths,while retaining important features of classical CNN,such as nonlinearity and scalability.We also present a framework to automatically compute the gradients of hybrid quantum-classical loss functions which could be directly applied to other hybrid quantum-classical algorithms.We demonstrate the potential of this architecture by applying it to a Tetris dataset,and show that QCCNN can accomplish classification tasks with learning accuracy surpassing that of classical CNN with the same structure.
基金Acknowledgements The authors acknowledge the use of IBM's Quantum Experience for this work. The views expressed are those of the author and do not reflect the official policy or position of IBM or the IBM Quantum Experience team, This project was supported by the National Basic Research Program of China (Grant No, 201acBaa8002), National Natural Science Foundation of China (Grant Nos. 11504430 and 61502526).
文摘Quantum computing has undergone rapid development in recent years. Owing to limitations on scalability, personal quantum computers still seem slightly unrealistic in the near future. The first practical quantum computer for ordinary users is likely to be on the cloud. However, the adoption of cloud computing is possible only if security is ensured. Homomorphic encryption is a cryptographic protocol that allows computation to be performed on encrypted data without decrypting them, so it is well suited to cloud computing. Here, we first applied homomorphic encryption on IBM's cloud quantum computer platform. In our experiments, we successfully implemented a quantum algorithm for linear equations while protecting our privacy. This demonstration opens a feasible path to the next stage of development of cloud quantum information technology.
基金supported by the National Natural Science Foundation of China(11475089 and 11875167)the Chinese Academy of Sciences,the National Fundamental Research Programthe China Postdoctoral Science Foundation(2018M630063)
文摘Since the pillars of quantum theory were established, it was already noted that quantum physics may allow certain correlations defying any local realistic picture of nature, as first recognized by Einstein,Podolsky and Rosen. These quantum correlations, now termed quantum nonlocality and tested by violation of Bell's inequality that consists of statistical correlations fulfilling local realism, have found loophole-free experimental confirmation. A more striking way to demonstrate the conflict exists, and can be extended to the multipartite scenario. Here we report experimental confirmation of such a striking way, the multipartite generalized Hardy's paradoxes, in which no inequality is used and the conflict is stronger than that within just two parties. The paradoxes we consider here belong to a general framework [S.-H. Jiang et al., Phys. Rev. Lett. 120(2018) 050403], including previously known multipartite extensions of Hardy's original paradox as special cases. The conflict shown here is stronger than in previous multipartite Hardy's paradox. Thus, the demonstration of Hardy-typed quantum nonlocality becomes sharper than ever.
基金supported by the National Basic Research Program of China (Grant No. 2013CB338002)the National Natural Science Foundation of China (Grant Nos. 11504430, and 61502526)
文摘Quantum algorithms can be used to efficiently solve certain classically intractable problems by exploiting quantum parallelism.However, the effectiveness of quantum entanglement in quantum computing remains a question of debate. This study presents a new quantum algorithm that shows entanglement could provide advantages over both classical algorithms and quantum algorithms without entanglement. Experiments are implemented to demonstrate the proposed algorithm using superconducting qubits.Results show the viability of the algorithm and suggest that entanglement is essential in obtaining quantum speedup for certain problems in quantum computing. The study provides reliable and clear guidance for developing useful quantum algorithms.