CNAM Colloquium: Kevin Osborn, UMD

Date
Thu, Dec 3, 2015 2:00 pm - 3:00 pm
Location
Room 1201 John S Toll Bldg

Description

SPEAKER: Kevin Osborn, UMD

TITLE: The Tunneling Atom Laser: Manipulating lossy two-level defects to produce coherent microwave gain in a resonator

ABSTRACT: Superconducting qubits have coherence limitations set by two-level system (TLS) defects which absorb microwave energy. These TLSs are known to arise in dielectric films such as native oxides, at material interfaces, etc. As a result, TLSs contribute to damping in qubits and related parametric amplifiers, where a Josephson junction is used for the nonlinearity. Here I will show a new method to adiabatically invert (excite) these same TLSs using a resonator which has no other significant nonlinearity. Pump fields are applied at detuned frequencies from the resonator, and with an additional sweeping dc field, the TLS population is generally inverted. When TLSs are inverted we find that they produce gain nonlinearity rather than a damping contribution. This occurs despite TLS randomness in multiple standard model parameters. We show that the threshold for lasing can be explained in terms of a cavity quantum electrodynamics model. Furthermore, with this control, the resonator is found to pass from the regime of ordinary defect loss, through a state of negligible material dissipation (and infinite quality factor), and finally to a regime of coherent microwave gain.