We present an alternative scheme to exactly implement one-qubit and two-qubit quantum gates with a single trapped cold ion driven by a travelling laser field. The internal degree of freedom of the ion acts as the targ...We present an alternative scheme to exactly implement one-qubit and two-qubit quantum gates with a single trapped cold ion driven by a travelling laser field. The internal degree of freedom of the ion acts as the target qubit and the control qubit is encoded by two Fock states of the external vibration of the ion. The conditions to realize these operations, including the duration of each applied laser pulse and Lamb-Dicke parameter, are derived. In our scheme neither the auxiliary atomic level nor the Lamb-Dicke approximation is required. The multiquantum transition between the internal and external degrees of freedom of the ion is considered.展开更多
An approach is proposed to implement the universal quantum gates between the ions confined individually in the separated traps.Instead of the typical adiabatic operations,performed for manipulating the ion-ion couplin...An approach is proposed to implement the universal quantum gates between the ions confined individually in the separated traps.Instead of the typical adiabatic operations,performed for manipulating the ion-ion coupling,here the switchable couplings between ions are implemented non-adiabatically by using the fast laser pulses.Consequently,the desirable quantum gates between the ions could be implemented by using only a series of laser pulses.The proposal may be conveniently generalized to the quantum computation with the scalable ion-traps.展开更多
Entangling multiple qubits is one of the central tasks of quantum information processing.We propose an approach to entangle a number of cold ions(individually trapped in a string of microtraps)by a moved cavity.The ca...Entangling multiple qubits is one of the central tasks of quantum information processing.We propose an approach to entangle a number of cold ions(individually trapped in a string of microtraps)by a moved cavity.The cavity is pushed to include the ions one by one with a uniform velocity and thus the information stored in former ions could be transferred to the latter ones by such a moving cavity bus.Since the positions of the trapped ions are precisely located,the strengths and durations of the ion-cavity interactions can be exactly controlled.As a consequence,by properly setting the relevant parameters,typical multi-ion entangled states,e.g.,W state for 10 ions,could be deterministically generated.The feasibility of the proposal is also discussed.展开更多
Persistent circulating currents in a mesoscopic open ring with side-branch structures are derived by transfer matrix method in the framework of quantum waveguide theory on networks.The behavior of transmission probabi...Persistent circulating currents in a mesoscopic open ring with side-branch structures are derived by transfer matrix method in the framework of quantum waveguide theory on networks.The behavior of transmission probability may show the Fano resonance in the presence of geometric scattering of side-branch structures.It is shown that persistent circulating currents in the main loop with equal length of both arms in the absence of magnetic Aux occur near the Fermi wave vectors where the Fano resonance appears.The numerical results show that a larger persistent current is associated with a stronger Fano resonance.The persistent circulating currents can be controlled by the Aux of side-branch structure.展开更多
We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates.Their microwave transmissions are measured at 20 mK....We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates.Their microwave transmissions are measured at 20 mK.It is found that these two types of resonators possess significantly different loaded quality factors;one is 5.6×10^(3) and the other is 4.0×10^(4).The measured data are fitted well by classical ABCD matrix approach and consequently the coupling capacitances are determined.It is found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.60076011,the Special Funds for Major State Basic Research Project under Grant No.2000683the Ministry of Science and Technology of China,the Shanghai Municipal Commission of Science and Technologythe Shanghai Foundation for Research and Development for Applied Materials。
文摘We present an alternative scheme to exactly implement one-qubit and two-qubit quantum gates with a single trapped cold ion driven by a travelling laser field. The internal degree of freedom of the ion acts as the target qubit and the control qubit is encoded by two Fock states of the external vibration of the ion. The conditions to realize these operations, including the duration of each applied laser pulse and Lamb-Dicke parameter, are derived. In our scheme neither the auxiliary atomic level nor the Lamb-Dicke approximation is required. The multiquantum transition between the internal and external degrees of freedom of the ion is considered.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11147116,10874142 and 90921010the National Basic Research Program of China under Grant No 2010CB923104the Open Project of State Key Laboratory of Functional Materials for Informatics.
文摘An approach is proposed to implement the universal quantum gates between the ions confined individually in the separated traps.Instead of the typical adiabatic operations,performed for manipulating the ion-ion coupling,here the switchable couplings between ions are implemented non-adiabatically by using the fast laser pulses.Consequently,the desirable quantum gates between the ions could be implemented by using only a series of laser pulses.The proposal may be conveniently generalized to the quantum computation with the scalable ion-traps.
基金by the National Natural Science Foundation of China under Grant Nos 10874142 and 90921010the National Basic Research Program of China under Grant No 2010CB923104.
文摘Entangling multiple qubits is one of the central tasks of quantum information processing.We propose an approach to entangle a number of cold ions(individually trapped in a string of microtraps)by a moved cavity.The cavity is pushed to include the ions one by one with a uniform velocity and thus the information stored in former ions could be transferred to the latter ones by such a moving cavity bus.Since the positions of the trapped ions are precisely located,the strengths and durations of the ion-cavity interactions can be exactly controlled.As a consequence,by properly setting the relevant parameters,typical multi-ion entangled states,e.g.,W state for 10 ions,could be deterministically generated.The feasibility of the proposal is also discussed.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19475017the Doctoral Education Fund of the State Education Commission of China under Grant No.9373010.
文摘Persistent circulating currents in a mesoscopic open ring with side-branch structures are derived by transfer matrix method in the framework of quantum waveguide theory on networks.The behavior of transmission probability may show the Fano resonance in the presence of geometric scattering of side-branch structures.It is shown that persistent circulating currents in the main loop with equal length of both arms in the absence of magnetic Aux occur near the Fermi wave vectors where the Fano resonance appears.The numerical results show that a larger persistent current is associated with a stronger Fano resonance.The persistent circulating currents can be controlled by the Aux of side-branch structure.
基金Supported by the National Natural Science Foundation of China under Grant No 11174373the National Basic Research Program of China under Grant No 2010CB923104.
文摘We design and fabricate two types of superconducting niobium coplanar waveguide microwave resonators with different coupling capacitors on high purity Si substrates.Their microwave transmissions are measured at 20 mK.It is found that these two types of resonators possess significantly different loaded quality factors;one is 5.6×10^(3) and the other is 4.0×10^(4).The measured data are fitted well by classical ABCD matrix approach and consequently the coupling capacitances are determined.It is found that the transmission peak deviates from the standard Lorentizian with a frequency broadening.