Device characterization of Si/SiGe double quantum dots using exchange oscillations in Earth's magnetic field
Abstract
Exchange-based semiconductor qubits encompass a broad family of encodings constructed from singlet- and triplet-like spin states, several of which are compatible with operation at zero applied magnetic field. Their reliable operation requires characterization of environmental noise, residual idle interactions, and exchange-dependent decay, but this characterization often relies on multi-axis control calibration or deliberately engineered magnetic-field gradients. A simpler zero-applied-field diagnostic is particularly valuable for hybrid semiconductor-superconductor systems, in which magnetic fields can degrade superconducting components. Here, we use the intrinsic magnetic-field gradient produced by residual nuclear spins in isotopically enriched Si/SiGe to implement exchange oscillations between two quantum dots as a characterization tool without a micromagnet, dynamic nuclear polarization, or prior multi-axis calibration. Using Carr-Purcell-Meiboom-Gill exchange sequences, we extend the singlet coherence from T2*=1.17±0.02 μs to T2CPMG=74.8±1.8 μs with N=70 refocusing pulses. The oscillation phase resolves residual exchange in the tens-of-kilohertz regime and enables it to be mapped across the (1,1) charge cell. These results establish intrinsic-gradient exchange oscillations as a simple, more relevant zero-field diagnostic for exchange-only and related semiconductor qubit encodings that is amenable to rapid, high-throughput device characterization.
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BibTeX
@misc{stemp2026device,
title = {{Device characterization of Si$/$SiGe double quantum dots using exchange oscillations in Earth's magnetic field}},
author = {Holly G. Stemp and Harry Hanlim Kang and Chih Hwan Yang and Gabriel D. Cutter and Frederike Brockmeyer and Patrick J. Strohbeen and Max Hays and Jeffrey A. Grover and William D. Oliver},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.31093},
eprint = {2608.31093},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.31093},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Device characterization of Si/SiGe double quantum dots using exchange oscillations in Earth's magnetic field
AU - Holly G. Stemp
AU - Harry Hanlim Kang
AU - Chih Hwan Yang
AU - Gabriel D. Cutter
AU - Frederike Brockmeyer
AU - Patrick J. Strohbeen
AU - Max Hays
AU - Jeffrey A. Grover
AU - William D. Oliver
PY - 2026
DA - 2026/08/31
PB - arXiv
DO - 10.48550/arxiv.2608.31093
UR - https://arxiv.org/abs/2608.31093
AB - Exchange-based semiconductor qubits encompass a broad family of encodings constructed from singlet- and triplet-like spin states, several of which are compatible with operation at zero applied magnetic field. Their reliable operation requires characterization of environmental noise, residual idle interactions, and exchange-dependent decay, but this characterization often relies on multi-axis control calibration or deliberately engineered magnetic-field gradients. A simpler zero-applied-field diagnostic is particularly valuable for hybrid semiconductor-superconductor systems, in which magnetic fields can degrade superconducting components. Here, we use the intrinsic magnetic-field gradient produced by residual nuclear spins in isotopically enriched Si/SiGe to implement exchange oscillations between two quantum dots as a characterization tool without a micromagnet, dynamic nuclear polarization, or prior multi-axis calibration. Using Carr-Purcell-Meiboom-Gill exchange sequences, we extend the singlet coherence from T_2^*=1.17±0.02 μs to T_2^CPMG=74.8±1.8 μs with N=70 refocusing pulses. The oscillation phase resolves residual exchange in the tens-of-kilohertz regime and enables it to be mapped across the (1,1) charge cell. These results establish intrinsic-gradient exchange oscillations as a simple, more relevant zero-field diagnostic for exchange-only and related semiconductor qubit encodings that is amenable to rapid, high-throughput device characterization.
ER -