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Quantum Measurements with Superconducting Circuits


Affiliations
1 Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
2 Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
 

We measure the state of a superconducting quantum bit (qubit) coupled to a microwave cavity by scattering a microwave signal from the cavity. The scattered signal is amplified using a low-noise Josephson parametric amplifier. We carried out measurements to infer the coherence properties of the qubit. In the strong measurement regime, we observe quantum jumps between the qubit states in real time, while we observe stochastic quantum trajectories in the weak measurement regime. The coherence times and measurement fidelity obtained are sufficient for implementing quantum error correction.

Keywords

Circuit QED, Coherence Properties, Qubits, Quantum Measurement, Superconducting Circuits.
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  • Quantum Measurements with Superconducting Circuits

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Authors

Tanay Roy
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
A. M. Vadiraj
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
Madhavi Chand
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
A. Ranadive
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
Suman Kundu
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
Meghan P. Patankar
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India
R. Vijay
Quantum Measurement and Control Laboratory, Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Mumbai 400 005, India

Abstract


We measure the state of a superconducting quantum bit (qubit) coupled to a microwave cavity by scattering a microwave signal from the cavity. The scattered signal is amplified using a low-noise Josephson parametric amplifier. We carried out measurements to infer the coherence properties of the qubit. In the strong measurement regime, we observe quantum jumps between the qubit states in real time, while we observe stochastic quantum trajectories in the weak measurement regime. The coherence times and measurement fidelity obtained are sufficient for implementing quantum error correction.

Keywords


Circuit QED, Coherence Properties, Qubits, Quantum Measurement, Superconducting Circuits.

References





DOI: https://doi.org/10.18520/cs%2Fv109%2Fi11%2F2069-2076