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QI: Fachverband Quanteninformation
QI 6: Implementations II
QI 6.3: Vortrag
Dienstag, 10. März 2026, 10:15–10:30, BEY/0245
Harnessing the non-Abelian Berry phase for universal control of zero-field spin qubits — •Baksa Kolok1,2, Csongor Hunyady1, and András Pályi1,2 — 1Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics — 2HUN-REN-BME-BCE Quantum Technology Research Group, Budapest University of Technology and Economics
Spin qubits in semiconductor quantum dots achieve their longest coherence times at zero magnetic field when nuclear spins are suppressed, making zero-field operation attractive. It also promises reduced control complexity by removing the need for magnets and enabling electrical, baseband manipulation. In this talk, I present a control framework that realizes universal quantum computation in sparse quantum-dot arrays operating entirely at zero magnetic field. Initialization and readout rely on singlet-triplet energy separation and Pauli spin blockade. Single-qubit gates emerge geometrically: when a qubit is shuttled around closed loops in the array, it accumulates a non-Abelian Berry phase that implements a deterministic SU(2) rotation. Although the number of accessible loops, and thus the native gate set, is discrete, we show that in generic devices two loops already provide full single-qubit controllability. Moreover, the same pair of loops suffices for complete quantum process tomography, enabling characterization of decoherence in zero-field architectures. Combined with exchange-based entangling gates, these results position sparse quantum-dot arrays as a promising platform for high-coherence, all-electric quantum computation without magnetic fields or microwave pulses.
Keywords: spin qubit; geometric phase; spin-orbit interaction; single-qubit gate; quantum process tomography