Reservoir- and Measurement-free Microwave Initialization of Semiconductor Spin Qubits
Abstract
Scalable quantum processors require repeated qubit initialization throughout large arrays. In semiconductor spin qubits, fast initialization commonly relies on local reservoir access or measurement-based feedback, requiring dedicated infrastructure that becomes increasingly difficult to distribute as processors scale. Here, we demonstrate reservoir- and measurement-free initialization of a silicon spin-qubit pair in an industrially fabricated Si/SiGe quantum-dot device using a fixed sequence of microwave and baseband pulses. Odd spin-parity states relax to the singlet charge state, whereas blocked even spin-parity states are microwave-driven through the triplet manifold and subsequently converted to the singlet by singlet-triplet mixing and charge hybridization. Repeated cycles produce the singlet-associated charge outcome with a median probability of 99.4% across the sampled preparation states, while exchange spectroscopy independently verifies mapping to the target |↑↓⟩ operational state. Microwave spectroscopy and time-domain measurements identify the dark-state-limited single-cycle transfer and the subsequent blockade-lifting dynamics that set the initialization time scale. The demonstrated pumping sequence uses approximately 12 μs of microwave bursts and mixing dwells, while we project sub-microsecond initialization under improved device conditions. These results establish fixed-sequence microwave initialization as a scalable control primitive for semiconductor spin-qubit processors, based on singlet-triplet physics that can be adapted to platforms with suitable Pauli-blockade transitions.
Related
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- Qubits Are Not Enough: Deflation and Measurement Limits in Variational Quantum Modal Analysis
BibTeX
@misc{camenzind2026reservoir,
title = {{Reservoir- and Measurement-free Microwave Initialization of Semiconductor Spin Qubits}},
author = {Leon C. Camenzind and Ik Kyeong Jin and Akito Noiri and Kenta Takeda and Takashi Nakajima and Takashi Kobayashi and Seigo Tarucha},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.39415},
eprint = {2609.39415},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.39415},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Reservoir- and Measurement-free Microwave Initialization of Semiconductor Spin Qubits
AU - Leon C. Camenzind
AU - Ik Kyeong Jin
AU - Akito Noiri
AU - Kenta Takeda
AU - Takashi Nakajima
AU - Takashi Kobayashi
AU - Seigo Tarucha
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.39415
UR - https://arxiv.org/abs/2609.39415
AB - Scalable quantum processors require repeated qubit initialization throughout large arrays. In semiconductor spin qubits, fast initialization commonly relies on local reservoir access or measurement-based feedback, requiring dedicated infrastructure that becomes increasingly difficult to distribute as processors scale. Here, we demonstrate reservoir- and measurement-free initialization of a silicon spin-qubit pair in an industrially fabricated Si/SiGe quantum-dot device using a fixed sequence of microwave and baseband pulses. Odd spin-parity states relax to the singlet charge state, whereas blocked even spin-parity states are microwave-driven through the triplet manifold and subsequently converted to the singlet by singlet-triplet mixing and charge hybridization. Repeated cycles produce the singlet-associated charge outcome with a median probability of 99.4% across the sampled preparation states, while exchange spectroscopy independently verifies mapping to the target |↑↓⟩ operational state. Microwave spectroscopy and time-domain measurements identify the dark-state-limited single-cycle transfer and the subsequent blockade-lifting dynamics that set the initialization time scale. The demonstrated pumping sequence uses approximately 12 μs of microwave bursts and mixing dwells, while we project sub-microsecond initialization under improved device conditions. These results establish fixed-sequence microwave initialization as a scalable control primitive for semiconductor spin-qubit processors, based on singlet-triplet physics that can be adapted to platforms with suitable Pauli-blockade transitions.
ER -