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Triplet-assisted leakage during singlet-triplet qubit readout with a quantum point contact

Karol Kawa*

  • *Contact author: kawa@fzu.cz
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Phys. Rev. B 114, 055302 – Published 28 July, 2026

DOI: https://doi.org/10.1103/szv1-sjgs

Abstract

Quantum point contact readout theory for singlet-triplet qubits in a lateral double quantum dot is extended by including tunneling of triplet configurations in a higher-energy level of the neighboring dot. This additional channel creates energetically allowed leakage pathways that modify the branch-dependent charge and current-noise signatures, even when the Pauli blockade remains effective within the ground-state manifold. The model contains two single-particle levels in each dot. The resulting singlet and triplet block structure is derived together with a Lindblad master equation. Quantum-jump simulations are then used to resolve the dynamics of individual readout events. A complementary Liouvillian steady-state analysis identifies the regime in which tunneling to the excited level qualitatively changes the readout signatures, with the crossover determined by the level spacing.

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Phys. Rev. B 114, 055302– Published 28 July, 2026
  • Received 6 May 2026
  • Accepted 8 July 2026
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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.

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