Heidelberg 2015 – scientific programme

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A: Fachverband Atomphysik

A 19: Precision Measurements and Metrology V (with Q)

A 19.6: Talk

Wednesday, March 25, 2015, 12:15–12:30, C/HSO

Dispersive Qubit Measurement by Interferometry with Parametric Amplifiers — •Shabir Barzanjeh, David DiVincenzo, and Barbara Terhal — Institute for Quantum Information, RWTH Aachen University, 52056 Aachen, Germany

We perform a detailed analysis of how an amplified interferometer can be used to enhance the quality of a dispersive qubit measurement, such as one performed on a superconducting transmon qubit, using homodyne detection on an amplified microwave signal. Our modeling makes a realistic assessment of what is possible in current circuit-QED experiments; in particular, we take into account the frequency-dependence of the qubit-induced phase shift for short microwaves pulses. We compare the possible signal-to-noise ratios obtainable with (single-mode) SU(1,1) interferometers with the current coherent measurement and find a considerable reduction in measurement error probability in an experimentally-accessible range of parameters.