A research team led by Professor Guo Guoping and Professor Cao Gang from the University of Science and Technology of China, Chinese Academy of Sciences, and Sigmund Kohler from the Institute of Materials Science in Madrid, created a response theory for strongly coupled multi-qubit systems. Their research results were recently published in the journal Physical Review Letters.
Researchers develop a new response theory for strongly coupled multi-qubit systems. This breakthrough addresses challenges faced in understanding periodicity-driven QD-Cavity hybrid systems.
Semiconductor quantum dots (QDs), which strongly couple with microwave photons, are key to studying light-matter interactions. In previous studies, the research team used high-impedance superconducting resonators to achieve strong coupling of quantum dot-cavity hybrid systems. Based on this strong coupling, the research team further studied circuit quantum electrodynamics (cQED) of periodically driven strongly coupled hybrid systems.
In this study, the researchers first prepared a high-impedance resonant cavity composite device integrating two double quantum dots (DQDs). By detecting the microwave response signal of a dual quantum dot-cavity hybrid system under periodic driving, they found that the existing dispersive cavity readout theory fails due to the enhancement of coupling strength.
Therefore, compared to existing theories, the researchers developed a new response theory that considers the cavity as part of the drive system. Using this theory, they successfully simulated and explained the signals in the experiment and further studied the dual DQD-cavity hybrid system under periodic driving.
This study opens a path to understanding periodic driven QD-cavity hybrid systems. In addition, the established theoretical method is not only applicable to hybrid systems with different coupling strengths, but can also be extended to multi-qubit systems.