A very simpJe theoretical scheme is proposed to implement two-and three-qubit controlled-phase gates firstly only using a single resonant interaction between ladder-type three-level atoms and the single-mode cavity. I...A very simpJe theoretical scheme is proposed to implement two-and three-qubit controlled-phase gates firstly only using a single resonant interaction between ladder-type three-level atoms and the single-mode cavity. In the presented protocol, the quantum information is encoded on the stable ground states of the atoms （as the controlling qubits） and the zero- and one-photon Fock states of cavity-field （as the target qubit）. Under the influence of the atomic spontaneous emission, the decay of the cavity-mode, and deviation of the coupling strength, the three-qubit controlled- phase gate may have a comparatively high fidelity. The experimental feasibility of controlled-phase gate and the ease that is extended to realize N-qubit controlled-phase gate are also discussed.展开更多
We present a two-step deterministic remote state preparation protocol for an arbitrary qubit with the aid of a three-particle Greenberger-Horne-Zeilinger state. Generalization of this protocol for higher-dimensional H...We present a two-step deterministic remote state preparation protocol for an arbitrary qubit with the aid of a three-particle Greenberger-Horne-Zeilinger state. Generalization of this protocol for higher-dimensional Hilbert space systems among three parties is also given. We show that only single-particle yon Neumann measurements, local operations, and classical communication are necessary. Moreover, since the overall information of the quantum state can be divided into two different pieces, which may be at different locations, this protocol may be useful in the quantum information field.展开更多
In data post-processing for quantum key distribution, it is essential to have a highly efficient error reconciliation protocol. Based on the key redistribution scheme, we analyze a one-way error reconciliation protoco...In data post-processing for quantum key distribution, it is essential to have a highly efficient error reconciliation protocol. Based on the key redistribution scheme, we analyze a one-way error reconciliation protocol by data simulation. The relationship between the error correction capability and the key generation efficiency of three kinds of Hamming code are demonstrated. The simulation results indicate that when the initial error rates are （0,1.5%], （1.5,4%], and （4,11%], using the Hamming （31,26）, （15,11）, and （7,4） codes to correct the error, respectively, the key generation rate will be maximized. Based on this, we propose a modified one-way error reconciliation protocol which employs a mixed Hamming code concatenation scheme. The error correction capability and key generation rate are verified through data simulation. Using the parameters of the posterior distribution based on the tested data, a simple method for estimating the bit error rate （BER） with a given confidence interval is estimated. The simulation results show that when the initial bit error rate is 10.00%, after 7 rounds of error correction, the error bits are eliminated completely, and the key generation rate is 10.36%; the BER expectation is 2.96×10^-10, and when the confidence is 95% the corresponding BER upper limit is 2.17×10^-9. By comparison, for the single （7,4） Hamming code error reconciliation scheme at a confidence of 95%,the key generation rate is only 6.09%, while the BER expectation is 5.92x 10＂9, with a BER upper limit of 4.34×10^-8. Hence, our improved protocol is much better than the original one.展开更多
To ensure a long-term quantum computational advantage,the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and hardwares.Here,we demonstrate a superconduct...To ensure a long-term quantum computational advantage,the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and hardwares.Here,we demonstrate a superconducting quantum computing systems Zuchongzhi 2.1,which has 66 qubits in a two-dimensional array in a tunable coupler architecture.The readout fidelity of Zuchongzhi 2.1 is considerably improved to an average of 97.74%.The more powerful quantum processor enables us to achieve larger-scale random quantum circuit sampling,with a system scale of up to 60 qubits and 24 cycles,and fidelity of FXEB=(3·66±0·345)×10^(-4).The achieved sampling task is about 6 orders of magnitude more difficult than that of Sycamore[Nature 574,505(2019)]in the classic simulation,and 3 orders of magnitude more difficult than the sampling task on Zuchongzhi 2.0[arXiv:2106.14734(2021)].The time consumption of classically simulating random circuit sampling experiment using state-of-the-art classical algorithm and supercomputer is extended to tens of thousands of years(about 4·8×104years),while Zuchongzhi 2.1 only takes about 4.2 h,thereby significantly enhancing the quantum computational advantage.展开更多
The first quantum private comparison(QPC) protocol via cavity quantum electrodynamics(QED) is proposed in this paper by making full use of the evolution law of atom via cavity QED, where the third party(TP) is allowed...The first quantum private comparison(QPC) protocol via cavity quantum electrodynamics(QED) is proposed in this paper by making full use of the evolution law of atom via cavity QED, where the third party(TP) is allowed to misbehave on his own but cannot conspire with either of the two users. The proposed protocol adopts two-atom product states rather than entangled states as the initial quantum resource, and only needs single-atom measurements for two users. Both the unitary operations and the quantum entanglement swapping operation are not necessary for the proposed protocol. The proposed protocol can compare the equality of one bit from each user in each round comparison with one two-atom product state. The proposed protocol can resist both the outside attack and the participant attack.Particularly, it can prevent TP from knowing two users' secrets. Furthermore, the qubit efficiency of the proposed protocol is as high as 50%.展开更多
Exploiting the optical excitation selection rules in graphene quantum dots, we investigate theoretically the entanglement generation process and entanglement concentration process of valley qubits. Our protocol shows ...Exploiting the optical excitation selection rules in graphene quantum dots, we investigate theoretically the entanglement generation process and entanglement concentration process of valley qubits. Our protocol shows that the graphene-based quantum dots can be distributed in a maximally entangled state through the interaction with single photons. In our proposed scheme, the setups are simplified as only single-photon detection is required. This provides a fast, all-optical manipulation of on-chip qubits,which gives an effective way for quantum information processing in graphene-based solid qubits.展开更多
We reinvestigate the one-way quantum deficit,which is a measure of quantum correlation emerging from a thermodynamical approach.We give a tight upper bound of the one-way quantum deficit for general mixed states,and g...We reinvestigate the one-way quantum deficit,which is a measure of quantum correlation emerging from a thermodynamical approach.We give a tight upper bound of the one-way quantum deficit for general mixed states,and give a sufficient condition for this bound.Finally,we discuss a universal way to evaluate the one-way quantum deficit for general two-qubit states.展开更多
We propose a one-step method to prepare multi-qubit GHZ and W states with transmon qubits capacitively coupled to a superconducting transmission line resonator(TLR).Compared with the scheme firstly introduced by Wang ...We propose a one-step method to prepare multi-qubit GHZ and W states with transmon qubits capacitively coupled to a superconducting transmission line resonator(TLR).Compared with the scheme firstly introduced by Wang et al.[Phys.Rev.B 81(2010) 104524],our schemes have longer dephasing time and much shorter operation time because the transmon qubits we used are not only more robust to the decoherence and the unavoidable parameter variations,but also have much stronger coupling constant with TLR.Based on the favourable properties of transmons and TLR,our method is more feasible in experiment.展开更多
基金Supported by Key Scientific Research Fund of Hunan Provincial Education Department of China under Grant No. 09A013Natural Science Foundation of Hunan Province of China under Grant No. 08J J3001Normal and Science Foundation of Hengyang Normal University of China under Grant No. 09A28
文摘A very simpJe theoretical scheme is proposed to implement two-and three-qubit controlled-phase gates firstly only using a single resonant interaction between ladder-type three-level atoms and the single-mode cavity. In the presented protocol, the quantum information is encoded on the stable ground states of the atoms （as the controlling qubits） and the zero- and one-photon Fock states of cavity-field （as the target qubit）. Under the influence of the atomic spontaneous emission, the decay of the cavity-mode, and deviation of the coupling strength, the three-qubit controlled- phase gate may have a comparatively high fidelity. The experimental feasibility of controlled-phase gate and the ease that is extended to realize N-qubit controlled-phase gate are also discussed.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10971247 and 10905016Hebei Natural Science Foundation of China under Grant Nos.F2009000311 and A2010000344 the Key Project of Science and Technology Research of Education Ministry of China under Grant No.207011
文摘We present a two-step deterministic remote state preparation protocol for an arbitrary qubit with the aid of a three-particle Greenberger-Horne-Zeilinger state. Generalization of this protocol for higher-dimensional Hilbert space systems among three parties is also given. We show that only single-particle yon Neumann measurements, local operations, and classical communication are necessary. Moreover, since the overall information of the quantum state can be divided into two different pieces, which may be at different locations, this protocol may be useful in the quantum information field.
基金supported in part by the Foundation for Key Program of Chinese Ministry of Education under Grant No.212177Scientific Research Foundation of the Education Department of Shaanxi Province under Grant No.12JK0973
文摘In data post-processing for quantum key distribution, it is essential to have a highly efficient error reconciliation protocol. Based on the key redistribution scheme, we analyze a one-way error reconciliation protocol by data simulation. The relationship between the error correction capability and the key generation efficiency of three kinds of Hamming code are demonstrated. The simulation results indicate that when the initial error rates are （0,1.5%], （1.5,4%], and （4,11%], using the Hamming （31,26）, （15,11）, and （7,4） codes to correct the error, respectively, the key generation rate will be maximized. Based on this, we propose a modified one-way error reconciliation protocol which employs a mixed Hamming code concatenation scheme. The error correction capability and key generation rate are verified through data simulation. Using the parameters of the posterior distribution based on the tested data, a simple method for estimating the bit error rate （BER） with a given confidence interval is estimated. The simulation results show that when the initial bit error rate is 10.00%, after 7 rounds of error correction, the error bits are eliminated completely, and the key generation rate is 10.36%; the BER expectation is 2.96×10^-10, and when the confidence is 95% the corresponding BER upper limit is 2.17×10^-9. By comparison, for the single （7,4） Hamming code error reconciliation scheme at a confidence of 95%,the key generation rate is only 6.09%, while the BER expectation is 5.92x 10＂9, with a BER upper limit of 4.34×10^-8. Hence, our improved protocol is much better than the original one.
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)。
文摘To ensure a long-term quantum computational advantage,the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and hardwares.Here,we demonstrate a superconducting quantum computing systems Zuchongzhi 2.1,which has 66 qubits in a two-dimensional array in a tunable coupler architecture.The readout fidelity of Zuchongzhi 2.1 is considerably improved to an average of 97.74%.The more powerful quantum processor enables us to achieve larger-scale random quantum circuit sampling,with a system scale of up to 60 qubits and 24 cycles,and fidelity of FXEB=(3·66±0·345)×10^(-4).The achieved sampling task is about 6 orders of magnitude more difficult than that of Sycamore[Nature 574,505(2019)]in the classic simulation,and 3 orders of magnitude more difficult than the sampling task on Zuchongzhi 2.0[arXiv:2106.14734(2021)].The time consumption of classically simulating random circuit sampling experiment using state-of-the-art classical algorithm and supercomputer is extended to tens of thousands of years(about 4·8×104years),while Zuchongzhi 2.1 only takes about 4.2 h,thereby significantly enhancing the quantum computational advantage.
基金Supported by the National Natural Science Foundation of China under Grant No.61402407
文摘The first quantum private comparison(QPC) protocol via cavity quantum electrodynamics(QED) is proposed in this paper by making full use of the evolution law of atom via cavity QED, where the third party(TP) is allowed to misbehave on his own but cannot conspire with either of the two users. The proposed protocol adopts two-atom product states rather than entangled states as the initial quantum resource, and only needs single-atom measurements for two users. Both the unitary operations and the quantum entanglement swapping operation are not necessary for the proposed protocol. The proposed protocol can compare the equality of one bit from each user in each round comparison with one two-atom product state. The proposed protocol can resist both the outside attack and the participant attack.Particularly, it can prevent TP from knowing two users' secrets. Furthermore, the qubit efficiency of the proposed protocol is as high as 50%.
基金supported by the National Natural Science Foundation of China(1140403161205117+3 种基金and61471050)Beijing Higher Education Young Elite Teacher Project(YETP0456)the Fundamental Research Funds for the Central Universities(2014RC0903)the State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications)
文摘Exploiting the optical excitation selection rules in graphene quantum dots, we investigate theoretically the entanglement generation process and entanglement concentration process of valley qubits. Our protocol shows that the graphene-based quantum dots can be distributed in a maximally entangled state through the interaction with single photons. In our proposed scheme, the setups are simplified as only single-photon detection is required. This provides a fast, all-optical manipulation of on-chip qubits,which gives an effective way for quantum information processing in graphene-based solid qubits.
基金Supported by National Natural Science Foundation of China under Grant Nos. 11271237 and 61228305
文摘We reinvestigate the one-way quantum deficit,which is a measure of quantum correlation emerging from a thermodynamical approach.We give a tight upper bound of the one-way quantum deficit for general mixed states,and give a sufficient condition for this bound.Finally,we discuss a universal way to evaluate the one-way quantum deficit for general two-qubit states.
基金Supported by the National Natural Science Foundation of China under Grant No. 10947017/A05Key Lab of Novel Thin Film Solar Cells (KF200912)Graduates’ Innovative Scientific Research Project of Zhejiang Province under Grant No. 2011831
文摘We propose a one-step method to prepare multi-qubit GHZ and W states with transmon qubits capacitively coupled to a superconducting transmission line resonator(TLR).Compared with the scheme firstly introduced by Wang et al.[Phys.Rev.B 81(2010) 104524],our schemes have longer dephasing time and much shorter operation time because the transmon qubits we used are not only more robust to the decoherence and the unavoidable parameter variations,but also have much stronger coupling constant with TLR.Based on the favourable properties of transmons and TLR,our method is more feasible in experiment.
