Coupling Of A 3D Cavity Qubit With Piezoelectric Material

With deeper understanding of the quantum world,more basic rules of quantum mechanics are applied to the life of human society.Quantum computers,which are totally different from the conventional ones,take advantage of the characteristics of quantum mechanics to achieve a faster computing.After decades of research,quantum computers have gradually been realized experimentally from an initial assumption.Among many quantum computer implementations,superconducting quantum computing is a unique one with excellent scalability,convenient controllability and acceptable coherence time.A lot of important progress have been made in this attractive research area,such as Sycamore with 53 qubits was released by Google in 2019.The main research of this article is to couple a qubit in a three-dimensional cavity(3D transmon)with piezoelectric material.The first part introduces the theory of 3D transmon and how to fabricate a 3D transmon in the lab.I briefly outline the physical parameters which should be considered in constructing a 3D transmon and how these parameters affect the characteristics of a3 D transmon.Then I discuss about how to realize such a qubit in the micro-machining center of School of Electronic Science and Engineering in Nanjing University.After continuous improvement,we have successfully obtained qubits with good performance and the related physical parameters have been measured.The second part is about the conversion of quantum information.Here we have tried to do the information conversion between a 3D transmon and a piezoelectric Al N oscillator.Such coupled system is realized with the similar micro-machining processes as those in fabricating a 3D transmon.Anti-crossings between the energy levels have been observed.Furthermore,we have extended the 3D to the planar structures to couple multiple qubits and piezoelectric vibrators.The third part is about the design of low-temperature infrared filters.With these filters,the infrared noise along the measuring circuit in the dilution refrigerator can be removed as much as possible to improve the accuracy of quantum measurement.