Continuous measurements for control of superconducting quantum circuits

Developments over the last two decades have opened the path towards quantum technologies in many quantum systems, such as cold atoms, trapped ions, cavity-quantum electrodynamics (QED), and circuit-QED. However, the fragility of quantum states to the effects of measurement and decoherence still pose...

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Bibliographic Details
Published in:Advances in physics: X 2020-01, Vol.5 (1), p.1813626
Main Authors: Hacohen-Gourgy, S., Martin, L. S.
Format: Article
Language:English
Subjects:
Circuit-QED
Circuits
Cold atoms
Cold traps
continuous measurement
Error correction
Error correction & detection
Fault tolerance
Feedback
Fragility
quantum control
Quantum electrodynamics
quantum feedback
Quantum mechanics
superconducting qubits
Trajectory measurement
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Summary:Developments over the last two decades have opened the path towards quantum technologies in many quantum systems, such as cold atoms, trapped ions, cavity-quantum electrodynamics (QED), and circuit-QED. However, the fragility of quantum states to the effects of measurement and decoherence still poses one of the greatest challenges in quantum technology. An imperative capability in this path is quantum feedback, as it enhances the control possibilities and allows for prolonging coherence times through quantum error correction. While changing parameters from shot to shot of an experiment or procedure can be considered feedback, quantum mechanics also allows for the intriguing possibility of performing feedback operations during the measurement process itself. This broader approach to measurements leads to the concepts of weak measurement, quantum trajectories, and numerous types of feedback with no classical analogs. These types of processes are the primary focus of this review. We introduce the concept of quantum feedback in the context of circuit-QED, an experimental platform with significant potential in quantum feedback and technology. We then discuss several experiments and see how they elucidate the concepts of continuous measurements and feedback. We conclude with an overview of coherent feedback, with application to fault-tolerant error correction.
ISSN:2374-6149
2374-6149
DOI:10.1080/23746149.2020.1813626