Emergence of highly coherent two-level systems in a noisy and dense quantum network
Abstract
Quantum sensors and qubits are usually two-level systems (TLS), the quantum analogues of classical bits assuming binary values 0 or 1. They are useful to the extent to which superpositions of 0 and 1 persist despite a noisy environment. The standard prescription to avoid decoherence of solid-state qubits is their isolation by means of extreme dilution in ultrapure materials. We demonstrate a different strategy using the rare-earth insulator LiY1−xTbxF4 (x = 0.001) which realizes a dense random network of TLS. Some TLS belong to strongly interacting Tb3+ pairs whose quantum states, thanks to localization effects, form highly coherent qubits with 100-fold longer coherence times than single ions. Our understanding of the underlying decoherence mechanisms—and of their suppression—suggests that coherence in networks of dipolar coupled TLS can be enhanced rather than reduced by the interactions.
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Acknowledgement
We thank Y. Polyhach for support with the spectrometer and M. Döbeli for Rutherford backscattering spectroscopy concentration measurements. We thank H. Sigg and J. Bailey for useful discussions. This work was financially supported by the Swiss National Science Foundation, grant nos. 200021_166271 (G.A. and M.M.) and P500PT_203179 (A.B.); Eidgenössische Technische Hochschule Zürich (grant no. ETH-48 16- 1 (G.J.)); and European Research Council under the European Union’s Horizon 2020 research and innovation programme HERO (grant agreement no. 810451 (G.A.)).
Contributions
A.B., M.G., R.T. and G.A. planned the experiments with inputs from all authors. S.G., G.M., M.M., G.J. and G.A. supervised the project. A.B., N.W. and R.T. adapted and operated the set-up. A.B. and N.W. performed the experiments and collected data. A.B., M.G. and N.W. analysed the data with inputs from all authors. M.G. and M.M. developed the theory and performed the simulations. A.B., M.G., M.M. and G.A. wrote the paper with input from all authors.
Data Availability
Source data are provided with this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.
Code Availability
The source codes used for the numerical simulations are provided with this paper.
Conflict of Interest
The authors declare no competing interests.
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Additional details
- ISSN
- 1745-2481
- URL
- https://rdcu.be/dwr5s
- Swiss National Science Foundation
- 200021_166271
- Swiss National Science Foundation
- P500PT_203179
- ETH Zurich
- ETH-48 16- 1
- European Research Council
- 810451
- Caltech groups
- Kavli Nanoscience Institute, Institute for Quantum Information and Matter