Student Support for Quantum Computation With Superconducting Quantum Devices

摘要

The research done by the graduate students on this grant focus on two topics: predominately, the focus was on the measurements of a persistent- current qubit driven by an on-chip radiation source, and secondarily on the fabrication of qubits for a fast turn around time. For the first topic the student preformed experiments of the monolithic integration of an onchip radiation source with a persistent-current (PC) qubit and dc SQUID measurement device. The devices were fabricated at MIT Lincoln Laboratory in a Nb/Al/AlOx/Nb trilayer process. The two PC qubit states were detected by measuring the switching current of an underdamped dc SQUID magnetometer inductively coupled to the qubit. The radiation source comprised an overdamped dc SQUID operating in the voltage state and inductively coupled to the qubit and measurement SQUID through a low-Q RLC filter. The oscillator was designed to have tunable amplitude and frequency to satisfy the requirements for coherent quantum manipulation of a superconducting PC qubit. Measurements were made in the millikelvin regime and the effects of the oscillator noise on the state of the qubit were obtained. For the second topic, work was done for implementing a fabrication process for superconducting qubits with a turn- around time of the order of a few weeks.