A general approach is proposed to the quantum Rabi model and its several variants within the extended coherent states.The solutions to all these models including the anisotropy and the nonlinear Stark coupling are the...A general approach is proposed to the quantum Rabi model and its several variants within the extended coherent states.The solutions to all these models including the anisotropy and the nonlinear Stark coupling are then obtained in an unified way.The essential characteristics such as the possible first-order phase transition can be detected analytically.This approach can be easily applied to the recent experiments with various tunable parameters without much additional effort,so it should be very helpful to the analysis of the experimental data.展开更多
Although the multi-level structure of superconducting qubits may result in calculation errors, it can be rationally used to effectively improve the speed of gate operations. Utilizing a current-biased Josephson juncti...Although the multi-level structure of superconducting qubits may result in calculation errors, it can be rationally used to effectively improve the speed of gate operations. Utilizing a current-biased Josephson junction （A-type rf-SQUID） as a tunable coupler for superconducting transmission line resonators （TLRs）, under the large detuning condition, we demonstrate the controllable generation of entangled coherent states in circuit quantum electrodynamics （circuit QED）. The coupling between the TLRs and the qubit can be effectively regulated by an external bias current or coupling capacitor. Further investigations indicate that the maximum entangled state can be obtained through measuring the excited state of the superconducting qubits. Then, the influence of the TLR [tecay on the prepared entangled states is analyzed.展开更多
We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artifi...We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artificial atom. When driving the cavity to a coherent state, the probe spectrum shows energy level splitting induced by the quantized electromagnetic field in the cavity. This splitting size is related to the coupling strength between the cavity and the artificial atom and, thus, is fixed after the sample is fabricated. This is in contrast to the classical Autler-Townes splitting of a three-level system in which the splitting is proportional to the driving amplitude, which can be continuously changed. Our experiment results show the difference between the classical microwave driving field and the quantum field of the cavity.展开更多
We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible phys...We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation,a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus,the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.展开更多
A fast scheme to generate Greenberger-Horne-Zeilinger states between different cavities in circuit QED systems is proposed.To implement this scheme,we design a feasible experimental device with three qubits and three ...A fast scheme to generate Greenberger-Horne-Zeilinger states between different cavities in circuit QED systems is proposed.To implement this scheme,we design a feasible experimental device with three qubits and three cavities.In this device,all the couplings between qubit and qubit,cavity and qubit are tunable and are independent with frequencies,and thus the shortcut to adiabaticity technique can be directly applied in our scheme.It is demonstrated that the GHZ state can be generated rapidly with high fidelity in our scheme.展开更多
We present an efficient scheme for the generation of NOON states of photons in circuit QED assisted by a superconducting charge qutrit.It is completed with two kinds of manipulations,that is,the resonant operation on ...We present an efficient scheme for the generation of NOON states of photons in circuit QED assisted by a superconducting charge qutrit.It is completed with two kinds of manipulations,that is,the resonant operation on the qutrit and the resonator,and the single-qubit operation on the qutrit,and they both are high-fidelity operations.Compared with the one by a superconducting transmon qutrit proposed by Su et al.(Sci Rep 4:3898,2014),our scheme does not require to maintain the qutrit in the third excited state with a long time,which relaxes the difficulty of its implementation in experiment.Moreover,the level anharmonicity of a charge qutrit is larger and it is better for us to tune the different transitions of the charge qutrit resonant to the resonator,which makes our scheme faster than others.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11834005 and 11674285).
文摘A general approach is proposed to the quantum Rabi model and its several variants within the extended coherent states.The solutions to all these models including the anisotropy and the nonlinear Stark coupling are then obtained in an unified way.The essential characteristics such as the possible first-order phase transition can be detected analytically.This approach can be easily applied to the recent experiments with various tunable parameters without much additional effort,so it should be very helpful to the analysis of the experimental data.
基金supported by the National Natural Science Foundation of China(Grant No.11264015)
文摘Although the multi-level structure of superconducting qubits may result in calculation errors, it can be rationally used to effectively improve the speed of gate operations. Utilizing a current-biased Josephson junction （A-type rf-SQUID） as a tunable coupler for superconducting transmission line resonators （TLRs）, under the large detuning condition, we demonstrate the controllable generation of entangled coherent states in circuit quantum electrodynamics （circuit QED）. The coupling between the TLRs and the qubit can be effectively regulated by an external bias current or coupling capacitor. Further investigations indicate that the maximum entangled state can be obtained through measuring the excited state of the superconducting qubits. Then, the influence of the TLR [tecay on the prepared entangled states is analyzed.
基金Project supported by the Science Funds from the Ministry of Science and Technology of China(Grant Nos.2014CB921401,2017YFA0304300,2014CB921202,and 2016YFA0300601)the National Natural Science Foundation of China(Grant No.11674376)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07010300)
文摘We couple a ladder-type three-level superconducting artificial atom to a cavity. Adjusting the artificial atom to make the cavity be resonant with the two upper levels, we then probe the lower two levels of the artificial atom. When driving the cavity to a coherent state, the probe spectrum shows energy level splitting induced by the quantized electromagnetic field in the cavity. This splitting size is related to the coupling strength between the cavity and the artificial atom and, thus, is fixed after the sample is fabricated. This is in contrast to the classical Autler-Townes splitting of a three-level system in which the splitting is proportional to the driving amplitude, which can be continuously changed. Our experiment results show the difference between the classical microwave driving field and the quantum field of the cavity.
基金Supported by the National Basic Research Program of China (Grant No. 2006CB921106)the National Natural Science Foundation of China (Grant No. 10874098)the ECIST-FET Project EuroSQUIP, the Swiss SNF, and the NCCR Nanoscience
文摘We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation,a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus,the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.
基金supported in part by the National Natural Science Foundation of China(NSFC)under Grant Nos.11974290 and 11875327the Natural Science Foundation of Guangdong Province under Grant No.2016A030313313+1 种基金the Fundamental Research Funds for the Central Universitiesthe Sun Yat-Sen University Science Foundation.
文摘A fast scheme to generate Greenberger-Horne-Zeilinger states between different cavities in circuit QED systems is proposed.To implement this scheme,we design a feasible experimental device with three qubits and three cavities.In this device,all the couplings between qubit and qubit,cavity and qubit are tunable and are independent with frequencies,and thus the shortcut to adiabaticity technique can be directly applied in our scheme.It is demonstrated that the GHZ state can be generated rapidly with high fidelity in our scheme.
基金supported by the National Natural Science Foundation of China (11174039)NECT-11-0031
文摘We present an efficient scheme for the generation of NOON states of photons in circuit QED assisted by a superconducting charge qutrit.It is completed with two kinds of manipulations,that is,the resonant operation on the qutrit and the resonator,and the single-qubit operation on the qutrit,and they both are high-fidelity operations.Compared with the one by a superconducting transmon qutrit proposed by Su et al.(Sci Rep 4:3898,2014),our scheme does not require to maintain the qutrit in the third excited state with a long time,which relaxes the difficulty of its implementation in experiment.Moreover,the level anharmonicity of a charge qutrit is larger and it is better for us to tune the different transitions of the charge qutrit resonant to the resonator,which makes our scheme faster than others.
