University of Oulu

Zanner, M., Orell, T., Schneider, C.M.F. et al. Coherent control of a multi-qubit dark state in waveguide quantum electrodynamics. Nat. Phys. 18, 538–543 (2022).

Coherent control of a multi-qubit dark state in waveguide quantum electrodynamics

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Author: Zanner, Maximilian1,2; Orell, Tuure3; Schneider, Christian M. F.1,2;
Organizations: 1Institute for Experimental Physics, University of Innsbruck, Innsbruck, Austria
2Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Innsbruck, Austria
3Nano and Molecular Systems Research Unit, University of Oulu, Oulu, Finland
4Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, Québec, Canada
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 8.8 MB)
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Language: English
Published: Springer Nature, 2022
Publish Date: 2022-09-14


Superconducting qubits in a waveguide have long-range interactions mediated by photons that cause the emergence of collective states. Destructive interference between the qubits decouples the collective dark states from the waveguide environment. Their inability to emit photons into the waveguide render dark states a valuable resource for preparing long-lived quantum many-body states and realizing quantum information protocols in open quantum systems. However, they also decouple from fields that drive the waveguide, making manipulation a challenge. Here we show the coherent control of a collective dark state that is realized by controlling the interactions between four superconducting transmon qubits and local drives. The dark state’s protection against decoherence results in decay times that exceed those of the waveguide-limited single qubits by more than two orders of magnitude. Moreover, we perform a phase-sensitive spectroscopy of the two-excitation manifold and reveal bosonic many-body statistics in the transmon array. Our dark-state qubit provides a starting point for implementing quantum information protocols with collective states.

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Series: Nature physics
ISSN: 1745-2473
ISSN-E: 1745-2481
ISSN-L: 1745-2473
Volume: 18
Pages: 538 - 543
DOI: 10.1038/s41567-022-01527-w
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
Funding: M.Z. and S.O. acknowledge funding by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (714235). M.Z. and C.M.F.S. acknowledge support by the Austrian Science Fund FWF within the DK-ALM (W1259-N27). R.A. acknowledges support from the Austrian Science Fund FWF within the SFB-BeyondC (F7106-N38). T.O. and M.S. acknowledge funding by the Emil Aaltonen Foundation and by the Academy of Finland (316619 and 320086). M.L.J. acknowledges funding from the Canada First Research Excellence Fund.
Academy of Finland Grant Number: 316619
Detailed Information: 316619 (Academy of Finland Funding decision)
320086 (Academy of Finland Funding decision)
Copyright information: © The Author(s), under exclusive licence to Springer Nature Limited 2022. This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: