Superconducting circuit realization of combinatorial gauge symmetry
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Published version
Date
2021-09-08
Authors
Chamon, Claudio
Green, Dmitry
Kerman, Andrew J.
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Published version
OA Version
Citation
C. Chamon, D. Green, A. Kerman. 2021. "Superconducting Circuit Realization of Combinatorial Gauge Symmetry." PRX Quantum, Volume 2, pp. 030341 - 030341 (15). https://doi.org/10.1103/PRXQuantum.2.030341
Abstract
We propose a superconducting quantum circuit based on a general symmetry principle—combinatorial gauge symmetry—designed to emulate topologically ordered quantum liquids and serve as a foundation for the construction of topological qubits. The proposed circuit exhibits rich features: in the classical limit of large capacitances its ground state consists of two superimposed loop structures; one is a crystal of small loops containing disordered U(1) degrees of freedom, and the other is a gas of loops of all sizes associated with Z2 topological order. We show that these classical results carry over to the quantum case, where phase fluctuations arise from the presence of finite capacitances, yielding Z2 quantum topological order. A key feature of the exact gauge symmetry is that amplitudes connecting different Z2 loop states arise from paths having zero classical energy cost. As a result, these amplitudes are controlled by dimensional confinement rather than tunneling through energy barriers. We argue that this effect may lead to larger energy gaps than previous proposals that are limited by such barriers, potentially making it more likely for a topological phase to be experimentally observable. Finally, we discuss how our superconducting circuit realization of combinatorial gauge symmetry can be implemented in practice.
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.