在超强耦合条件下对量子比特纠缠保持的研究

Investigation on Maintaining Entanglement of Two Qubits in Ultrastrong Coupling Region

研究了与处于相干态的量子谐振腔相耦合的,具有相互作用的两个量子比特的动力学问题。量子比特与量子谐振腔之间处于超强耦合并且它们之间的失谐量很大。利用绝热近似的方法,可以通过选择量子谐振腔相干态的平均粒子数、量子谐振腔与量子比特的耦合强度、量子谐振腔以及量子比特各自的频率和量子比特之间的相互作用强度这4个参数,来保持量子比特的纠缠。如果量子比特之间的相互作用强度为负数,可以使它们之间的纠缠保持很长时间。这些结果不同于之前的研究,并做出了对应的解释。保持纠缠使得上述结果可能会应用到量子信息处理中。

The dynamics of two qubits with inter-qubit interaction is investigated by an external quantum oscillator in its coherent state. The coupling between the two qubits and the oscillator is in the ultra-strong region and their detuning is large. With adiabatic approximation method, the reservation of one initially entangled state of two qubits by the quantum oscillator is accomplished through the careful choice of the four parameters, the average number of the coherent state of oscillator, the ultra-strong coupling strength, the ratio of two frequencies of qubit and oscillator, and the inter-interaction coupling of two qubits. If the inter-qubit interaction strength is negative, their entanglement can be kept further for a much longer time. These results are different from those in the previous studies and reasonable explanations are given. Maintaining the entanglement of two qubits with very high fidelity will be helpful for the quantum information process.