Direct measurement of the energy spectrum of a quantum dot qubit

Quantum Physics [Submitted on 31 Mar 2026] Direct measurement of the energy spectrum of a quantum dot qubit J. Reily, Daniel J. King, Jonathan C. Marcks, M.A. Wolfe, Piotr Marciniec, E.S. Joseph, Tyler J. Kovach, Brighton X. Coe, Mark Friesen, Benjamin D. Woods, M.A. Eriksson The mapping between gate voltages applied to a double quantum dot, and the parameters of a Hubbard-like Hamiltonian, is of utmost importance for understanding and operating spin qubits. State-of-the-art techniques for measuring Hamiltonian parameters (e.g., detuning axis pulsed spectroscopy, DAPS) provide details about energy levels; however, tunnel coupling estimates typically reveal only a small portion of the full Hamiltonian. Here, we demonstrate a Hamiltonian-agnostic technique for measuring the double dot energy spectrum over a wide energy range, at every value of the detuning, called delta-axis spectroscopy (DAXS). We apply the DAXS method to obtain the energy spectrum of a Si/SiGe double quantum dot and use this data to extract the diagonal and off-diagonal couplings of a 15-level Hubbard-like Hamiltonian, demonstrating very good agreement with the experimental measurements. Comments: 13 pages, including supplemental materials Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.29229 [quant-ph]   (or arXiv:2603.29229v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.29229 Focus to learn more Submission history From: Mark Friesen [view email] [v1] Tue, 31 Mar 2026 03:52:32 UTC (8,050 KB) Access Paper: view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)