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arXiv · 2510.20127

Electronically-controlled one- and two-qubit gates for transmon quasicharge qubits

Nicholas M. Christopher·Deniz E. Stiegemann·Abhijeet Alase·Thomas M. Stace
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Abstract

Superconducting protected qubits aim to achieve sufficiently low error rates so as to allow realization of error-corrected, utility-scale quantum computers. A recent proposal encodes a protected qubit in the quasicharge degree of freedom of the conventional transmon device. Operating such a protected `quasicharge qubit' requires implementing new strategies. Here we show that an electronically-controllable tunnel junction formed by two topological superconductors can be used to implement single- and two-qubit gates on quasicharge qubits. Schemes for both these gates are based on the same dynamical $4\pi$-periodic Josephson effect and therefore have the same gate times and error characteristics. We simulate the dynamics of a topological Josephson junction in a parameter regime with non-negligible charging energy, and characterize the robustness of such gate operations against charge noise. Our results point to a compelling strategy for implementation of quasicharge qubit gates based on junctions of minimal Kitaev chains of quantum dots.

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Nicholas M. Christopher, Deniz E. Stiegemann, Abhijeet Alase, Thomas M. Stace. 2025-10-23. Electronically-controlled one- and two-qubit gates for transmon quasicharge qubits. https://arxiv.org/abs/2510.20127

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