Liu Yu-xi, You J Q, Wei L F, Sun C P, Nori Franco
Frontier Research System, The Institute of Physical and Chemical Research (RIKEN), Wako-shi 351-0198, Japan.
Phys Rev Lett. 2005 Aug 19;95(8):087001. doi: 10.1103/PhysRevLett.95.087001. Epub 2005 Aug 17.
We analyze the optical selection rules of the microwave-assisted transitions in a flux qubit superconducting quantum circuit (SQC). We show that the parities of the states relevant to the superconducting phase in the SQC are well defined when the external magnetic flux phi(e) = phi(0)/2; then the selection rules are the same as the ones for the electric-dipole transitions in usual atoms. When phi(e) does not = phi(0)/2, the symmetry of the potential of the artificial "atom" is broken, a so-called delta-type "cyclic" three-level atom is formed, where one- and two-photon processes can coexist. We study how the population of these three states can be selectively transferred by adiabatically controlling the electromagnetic field pulses. Different from lambda-type atoms, the adiabatic population transfer in our three-level delta atom can be controlled not only by the amplitudes but also by the phases of the pluses.
我们分析了磁通量子比特超导量子电路（SQC）中微波辅助跃迁的光学选择规则。我们表明，当外部磁通量$\phi(e)=\phi(0)/2$时，SQC中与超导相位相关的态的宇称定义良好；此时选择规则与普通原子中电偶极跃迁的选择规则相同。当$\phi(e)\neq\phi(0)/2$时，人工“原子”势的对称性被打破，形成了所谓的$\delta$型“循环”三能级原子，其中单光子和双光子过程可以共存。我们研究了如何通过绝热控制电磁场脉冲来选择性地转移这三个态的布居。与$\lambda$型原子不同，我们的三能级$\delta$原子中的绝热布居转移不仅可以通过脉冲的幅度来控制，还可以通过脉冲的相位来控制。
