Zheng Fulu, Shen Yuejun, Sun Kewei, Zhao Yang
Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden, Germany.
Division of Materials Science, Nanyang Technological University, Singapore 639798, Singapore.
J Chem Phys. 2021 Jan 28;154(4):044102. doi: 10.1063/5.0033545.
We investigate multiple photon-assisted Landau-Zener (LZ) transitions in a hybrid circuit quantum electrodynamics device in which each of two interacting transmission-line resonators is coupled to a qubit, and the qubits are driven by periodic driving fields and also coupled to a common phonon mode. The quantum state of the entire composite system is modeled using the multi-DAnsatz in combination with the time-dependent Dirac-Frenkel variational principle. Applying a sinusoidal driving field to one of the qubits, this device is an ideal platform to study the photon-assisted LZ transitions by comparing the dynamics of the two qubits. A series of interfering photon-assisted LZ transitions takes place if the photon frequency is much smaller than the driving amplitude. Once the two energy scales are comparable, independent LZ transitions arise and a transition pathway is revealed using an energy diagram. It is found that both adiabatic and nonadiabatic transitions are involved in the dynamics. Used to model environmental effects on the LZ transitions, the common phonon mode coupled to the qubits allows for more available states to facilitate the LZ transitions. An analytical formula is obtained to estimate the short time phonon population and produces results in reasonable agreement with numerical calculations. Equipped with the knowledge of the photon-assisted LZ transitions in the system, we can precisely manipulate the qubit state and successfully generate the qubit dynamics with a square-wave pattern by applying driving fields to both qubits, opening up new venues to manipulate the states of qubits and photons in quantum information devices and quantum computers.
我们研究了混合电路量子电动力学器件中的多光子辅助朗道-齐纳（LZ）跃迁。在该器件中，两个相互作用的传输线谐振器分别与一个量子比特耦合，量子比特由周期性驱动场驱动，并且还与一个共同的声子模式耦合。整个复合系统的量子态使用多D近似结合含时狄拉克-弗伦克尔变分原理进行建模。通过向其中一个量子比特施加正弦驱动场，该器件是通过比较两个量子比特的动力学来研究光子辅助LZ跃迁的理想平台。如果光子频率远小于驱动幅度，会发生一系列干涉性光子辅助LZ跃迁。一旦两个能量尺度可比，就会出现独立的LZ跃迁，并使用能量图揭示跃迁路径。研究发现，动力学过程中涉及绝热跃迁和非绝热跃迁。与量子比特耦合的共同声子模式用于模拟环境对LZ跃迁的影响，它允许更多的可用状态来促进LZ跃迁。得到了一个解析公式来估计短时间的声子布居数，其结果与数值计算结果合理一致。基于对系统中光子辅助LZ跃迁的了解，我们可以精确地操纵量子比特状态，并通过向两个量子比特施加驱动场成功地产生具有方波模式的量子比特动力学，为在量子信息器件和量子计算机中操纵量子比特和光子的状态开辟了新途径。
