研究了两个(σ)1z(×)(σ)2z Ising型耦合量子比特的能级,这是一种典型的赝自旋约瑟夫森结比特模型.论述了两个磁通量子比特通过耦合可以构成量子力学四能级系统;研究了两量子比特间主要因子含能量差ε,隧穿幅度t和耦合因子j(包括耦合强度和耦合方向)对能级的影响.结果表明:对于由两个相同量子比特构成的系统,在φ＝(1/2)φ处,不仅两抗铁磁态的能级受控于耦合因子,它们之间的跃迁频率也由耦合因子控制.
We investigate the energy levels of two qubits that are coupled via (σ)1z (×)(σ)2z Ising-type of coupling. We demonstrate that two flux qubits can be coupled to form a quantum mechanical four level system. We not only investigate how the energy bias ε and tunneling amplitude t affect the energy levels, but also especially analyze the effect of the coupling factor j (both coupling strength and coupling direction) between two qubits. The results indicate that, for a two identical qubits system, not only the energy level of two antiferromagnetic states but also the transition frequency between them at φ = (1/2)φ0 is controlled by the coupling factors.
参考文献
| [1] | Chiorescu I,Bertet P,Semba K,et al.Coherent dynamics of a flux qubit coupled to a harmonic oscillator[J].Nature,2004,431:159. |
| [2] | Yu Y,Han S,et al.Coherent temporal oscillations of macroscopic quantum states in a Josephson junction[J].Science,2002,296:889. |
| [3] | Majer J B,Paauw F G,Haar A C J ter,et al.Spectroscopy on two coupled superconducting flux qubits[J].Phys.Rev.Lett.,2005,94:090501. |
| [4] | Nakamura Y,Pashkin Yu A,Tsai J S.Coherent control of macroscopic quantum states in a single-Cooper-pair box[J].Nature,1999,398:786. |
| [5] | Martinis J M,Nam S,Aumentado J,et al.Rabi oscillations in a large Josephson-junction qubit[J].Phys.Rev.Lett.,2002,89:117901. |
| [6] | Friedman J R,Patel V,Chen W,et al.Quantum superposition of distinct macroscopic states[J].Nature,2000,406:43. |
| [7] | Amin M H S,Smirnov A Y,Maassen van den Brink A.Josephson-phase qubit without tunneling[J].Phys.Rev.B,2003,67:100508. |
| [8] | Kis Z,Paspalakis E.Arbitrary totation and entanglement of flux SQUID qubits[J].Phys.Rev.B,2004,69:024510. |
| [9] | Zhang P,Wang Z D,Sun J D,et al.Quantum logic gate operation and entanglement with superconducting quantum interferencedevices in a cavity via a Raman transition[J].Phys.Rev.A,2005,71:052310. |
| [10] | Yang C P,Chu Shih-I,Han S.Possible realization of entanglement,logical gates,and quantum-information transfer with superconducting-quantum-interference-device qubits in cavity QED[J].Phys.Rev.A,2003,67:042311. |
| [11] | Wal C H van der,Haar A C J ter,Wilhelm F K,et al.Quantum superposition of macroscopic persistent-current states[J].Science,2000,290:773. |
| [12] | Chiorescu I,Nakamura Y,et al.Coherent quantum dynamics of a superconducting flux qubit[J].Science,2003,299:1869. |
| [13] | Pashkin Yu A,Yamamoto T,Astafiev O,et al.Quantum oscillations in two coupled charge qubits[J].Nature (London),2003,421:823. |
| [14] | Berkley A J,Xu H,Ramos R C,et al.Entangled macroscopic quantum states in two superconducting qubits[J].Science,2003,300:1548. |
| [15] | van der Wal C H,Wilhelm F K,Harmans C J P M,et al.Engineering decoherence in Josephson persistent-current qubits:measurement apparatus and other electromagnetic environments[J].Eur.Phys.J.B.,2003,31:111. |
| [16] | Ralph J F,Clark T D,Spiller T P,et al.Entanglement generation in persistent current qubits[J].Phys.Rev.B,2004,70:144527. |
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