Measurements of a Persistent-Current Qubit Driven by an On-Chip Radiation Source

Monolithic integration of control electronics with superconducting qubits will facilitate scalability of a superconducting quantum computer by reducing the room temperature electronics necessary for performing quantum state manipulation. We report the experimental results of the monolithic integration of an on-chip 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. We will discuss the measurements in the millikelvin regime and the effects of the oscillator noise on the state of the qubit.