Recovering quantum coherence of a cavity qubit through environment monitoring and active feedback

Uri Goldblatt, Nitzan Kahn, Sergey Hazanov, Ofir Milul, Barkay Guttel, Lalit M. Joshi, Daniel Chausovsky, Fabien Lafont, Serge Rosenblum

Research output: Contribution to journalArticle


Decoherence in qubits, caused by their interaction with a noisy environment, poses a significant challenge to developing reliable quantum processors. Monitoring the qubit's environment enables not only to identify decoherence events but also to reverse these errors, thereby restoring the qubit coherence. This approach is particularly beneficial for superconducting cavity qubits, whose unavoidable interaction with auxiliary transmons impacts their coherence. In this work, we uncover the intricate dynamics of cavity decoherence by tracking the noisy trajectory of a transmon acting as the cavity's environment. Using real-time feedback, we successfully recover the lost coherence of the cavity qubit, achieving a fivefold increase in its dephasing time. Alternatively, by detecting transmon errors and converting them into erasures, we improve the cavity phase coherence by more than an order of magnitude. These advances are essential for implementing long-lived cavity qubits with high-fidelity gates and can enable more efficient bosonic quantum error correction codes.
Original languageEnglish
Number of pages17
StateIn preparation - 4 Mar 2024


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