Enhanced coherence of a quantum doublet coupled to Tomonaga-Luttinger liquid leads |
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Authors: | Antonio Cirillo Matteo Mancini Domenico Giuliano Pasquale Sodano |
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Affiliation: | a Dipartimento di Fisica, Università di Perugia, Via A. Pascoli, I-06123, Perugia, Italy b I.N.F.N., Sezione di Perugia, Via A. Pascoli, I-06123, Perugia, Italy c Dipartimento di Fisica, Università della Calabria, Arcavacata di Rende I-87036, Cosenza, Italy d I.N.F.N., Gruppo Collegato di Cosenza, Arcavacata di Rende I-87036, Cosenza, Italy e Perimeter Institute for Theoretical Physics, 31 Caroline St. N, Waterloo ON, N2L 2Y5, Canada |
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Abstract: | We use boundary field theory to describe the phases accessible to a tetrahedral qubit coupled to Josephson junction chains acting as Tomonaga-Luttinger liquid leads. We prove that, in a pertinent range of the fabrication and control parameters, an attractive finite coupling fixed point emerges due to the geometry of the composite Josephson junction network. We show that this new stable phase is characterized by the emergence of a quantum doublet which is robust not only against the noise in the external control parameters (magnetic flux, gate voltage) but also against the decoherence induced by the coupling of the tetrahedral qubit with the superconducting leads. We provide protocols allowing to read and to manipulate the state of the emerging quantum doublet and argue that a tetrahedral Josephson junction network operating near the new finite coupling fixed point may be fabricated with today?s technologies. |
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Keywords: | Boundary critical phenomena Josephson junction arrays Quantum impurity models |
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