Irfan Siddiqi, University of California, Berkeley
Abstract
Great advances have been made in superconducting qubit technology since the first demonstration of coherent oscillations more than 10 years ago. Coherence times have improved by several orders of magnitude, basic gate operations and three qubit entanglement have been demonstrated, but the continuous, high-fidelity monitoring of the qubit state has remained an elusive target. This functionality can play a key role in quantum state feedback, and in particular qubit error correction. We realize such a readout using a wide bandwidth, phase-sensitive parametric amplifier operating near the quantum noise limit. With this level of sensitivity, quantum jumps between the qubit states in a transmon and in a flux qubit are readily resolved in real time. I will discuss the statistics of the quantum jumps as well as the evolution of the qubit under simultaneous measurement and excitation.