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Publication Citation: Measurement crosstalk between two phase qubits coupled by a coplanar waveguide

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Author(s): Fabio Altomare; Katarina Cicak; Mika A. Sillanpaa; Michael S. Allman; Dale Li; Adam J. Sirois; Joshua Strong; Jae Park; Jed D. Whittaker; Raymond W. Simmonds;
Title: Measurement crosstalk between two phase qubits coupled by a coplanar waveguide
Published: September 14, 2010
Abstract: We investigate measurement crosstalk in a system with two flux-biased phase qubits coupled by a resonant coplanar waveguide cavity. After qubit measurement, the superconducting phase undergoes damped oscillations in a deep anharmonic potential producing a frequency chirped voltage or crosstalk signal. We show experimentally that a coplanar waveguide cavity acts as a bandpass filter that can significantly reduce the propagation of this crosstalk signal when the qubits are far off resonance from the cavity. The transmission of the crosstalk signal ∝(ωqCx)2 can be further minimized by reducing the qubit frequencies and the coupling capacitance to the cavity. We model the large amplitude crosstalk signal and qubit response classically with results that agree well with the experimental data. We find that the maximum energy transferred by the crosstalk generating qubit roughly saturates for long energy relaxation times (T1>100 ns) while the delay time necessary for the crosstalk signal to propagate to the cavity scales linearly with T1. Ultimately, the use of resonant cavities as coupling elements and crosstalk filters is extremely beneficial for future architectures incorporating many coupled qubits.
Citation: Physical Review B
Volume: 82
Issue: 9
Pages: 7 pp.
Research Areas: Quantum Information and Measurements, Superconductors
PDF version: PDF Document Click here to retrieve PDF version of paper (693KB)