提出了一个利用处在线性阱中的两个全同的三能级离子与两个不同频率的激光脉冲共振相互作用来实现两比特量子SWAP门的方案,该方案是根据Haffner和Riebe等的实验方法与结果选择40Ca+离子S1/2基态的一个塞曼能级作为基态,以亚稳态D5/2的两个塞曼能级作为两个激发态来实现的,选择适当的参数如质心模的频率v=1.2 MHz,拉比频率Ω=0.1v以及Lamb-Dicke参数η=0.1,计算出实现该方案所用的总时间为T≈1.3×10-3S,该时间远小于亚稳态D5/2的寿命T1≈1.16 S,并且在这个方案里消相干是可以被忽略的.在目前的离子阱技术条件下,该方案是可以实现的.
A novel scheme for realizing a two-qubit quantum SWAP gate in ion-trap systems is proposed. Two three-level ions are considered which are confined in a linear trap interacting with two different frequency laser pulse in the case of resonance. According to the experimental methods and results of Haffner and Riebe, one Zeeman level of the S1/2 ground state of 40Ca+ ion can act as one ground state, while two Zeeman levels of the metastable D5/2 state as the excited states.With choosing appropriate parameters such as V=1.2 MHz, Ω=0.1 V and η=0.1, the total timerequired to complete the procedure is T ≈1.3～10-3s, much shorter than the lifetime Tl≈1.16 sof the metastable D5/2 state, and in this scheme decoherence is negligible. Thus this scheme may be realized with presently available ion-trap techniques.
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