Active protection of a superconducting qubit with an interferometric Josephson isolator

Nonreciprocal microwave devices play critical roles in high-fidelity, quantum-nondemolition (QND) measurement schemes. They impose unidirectional routing of readout signals and protect the quantum systems from unwanted noise originated by the output chain. However, cryogenic circulators and isolator...

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Bibliographic Details
Published in:Nature communications 2019-07, Vol.10 (1), p.3154-10, Article 3154
Main Authors: Abdo, Baleegh, Bronn, Nicholas T., Jinka, Oblesh, Olivadese, Salvatore, Córcoles, Antonio D., Adiga, Vivekananda P., Brink, Markus, Lake, Russell E., Wu, Xian, Pappas, David P., Chow, Jerry M.
Format: Article
Language:English
Subjects:
639/766/1130/1064
639/766/483/2802
Accuracy
Chains
Circuits
Humanities and Social Sciences
Interferometry
Isolators
Magnetic fields
Magnetic materials
Mixers
multidisciplinary
Noise
Noise levels
Qubits (quantum computing)
Routing
Science
Science (multidisciplinary)
Superconductivity
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Summary:Nonreciprocal microwave devices play critical roles in high-fidelity, quantum-nondemolition (QND) measurement schemes. They impose unidirectional routing of readout signals and protect the quantum systems from unwanted noise originated by the output chain. However, cryogenic circulators and isolators are disadvantageous in scalable superconducting architectures because they use magnetic materials and strong magnetic fields. Here, we realize an active isolator formed by coupling two nondegenerate Josephson mixers in an interferometric scheme and driving them with phase-shifted, same-frequency pumps. By incorporating our Josephson-based isolator into a superconducting qubit setup, we demonstrate fast, high-fidelity, QND measurements of the qubit while providing 20 dB of protection within a bandwidth of 10 MHz against amplified noise reflected off the Josephson amplifier in the output chain. A moderate reduction of 35% is observed in T 2E when the Josephson-based isolator is turned on. Such a moderate degradation can be mitigated by minimizing heat dissipation in the pump lines. Magnetic-based isolators are critical components for protecting qubits against noise in quantum setups but unsuitable for large processors. Here, Abdo et al. show good protection of a qubit in a high-fidelity quantum readout setup using a Josephson-based isolator devoid of magnetic materials.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-019-11101-3