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arxiv: 2604.24090 · v1 · submitted 2026-04-27 · 🪐 quant-ph · cond-mat.mes-hall· cond-mat.mtrl-sci

Electrically detected magnetic resonance of ⁷⁵As magnetic clock transitions in silicon

Ravi Acharya (1 , 2 , 3) , Shao Qi Lim (1 , 4 , 5) , Brett C. Johnson (5) , Nicholas Gillespie (1
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Christopher T.-K. Lew (5) Alexander M. Jakob (1 4) Daniel L. Creedon (6) Gus O. Bonin (1) Dane R. McCamey (7) Richard J. Curry (2) Jeffrey C. McCallum (1 David N. Jamieson (1 4) ((1) School of Physics University of Melbourne Parkville Australia (2) Photon Science Institute Department of Electrical Electronic Engineering University of Manchester Manchester United Kingdom (3) London Centre for Nanotechnology University College London London United Kingdom (4) Australian Research Council Centre for Quantum Computation Communication Technology (5) Department of Physics School of Science RMIT University Melbourne Australia (6) CSIRO Manufacturing Clayton Australia (7) School of Physics University of New South Wales Sydney Australia)
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Pith reviewed 2026-05-08 04:08 UTC · model grok-4.3

classification 🪐 quant-ph cond-mat.mes-hallcond-mat.mtrl-sci
keywords electrically detected magnetic resonancemagnetic clock transitionsarsenic-75 donorssilicon spin systemslinewidth broadeningdonor Hamiltoniannear-surface donorsquantum device coherence
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The pith

Low-field EDMR detects magnetic clock transitions in near-surface 75As donors in silicon by observing linewidth broadening.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that magnetic clock transitions, where spin transition frequencies lose first-order sensitivity to magnetic field changes, can be observed in ensembles of arsenic-75 donors near silicon surfaces. Using continuous-wave electrically detected magnetic resonance at fields below 10 millitesla, the resonance signals exhibit clear broadening as the clock condition is neared. This broadening matches predictions from a model based on the donor spin Hamiltonian. The work positions low-field EDMR as a practical way to study these decoherence-suppressing transitions in donor systems that sit close to surfaces, which are central to silicon quantum device designs.

Core claim

Magnetic clock transitions from an ensemble of near-surface 75As (I = 3/2) spins in silicon are observed using low-field (< 10 mT) continuous-wave electrically detected magnetic resonance (EDMR). As the CT condition is approached, pronounced linewidth broadening is observed, consistent with a donor Hamiltonian informed linewidth model. These results establish low-field EDMR as a sensitive probe of CTs in near-surface donor systems relevant to silicon-based quantum devices.

What carries the argument

the donor Hamiltonian informed linewidth model, which accounts for the increase in resonance linewidth as the magnetic field tunes toward the clock transition where first-order field sensitivity vanishes.

If this is right

  • Clock transitions suppress decoherence in donor spin systems by eliminating linear magnetic-field noise coupling.
  • Low-field EDMR can locate and characterize clock transitions in near-surface donor ensembles.
  • The approach applies directly to silicon-based quantum devices where surface-proximate donors are used.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same EDMR method could map clock transitions for other donors such as phosphorus or antimony in silicon.
  • Surface-specific broadening data may inform donor placement strategies that preserve longer coherence times.
  • Extension to pulsed EDMR variants might allow direct coherence measurements at the clock condition.

Load-bearing premise

The observed linewidth broadening arises specifically from approaching the clock transition condition according to the donor Hamiltonian rather than from unrelated experimental artifacts or other broadening sources.

What would settle it

No linewidth broadening, or a broadening pattern that fails to match the donor Hamiltonian predictions, when the magnetic field is swept through the calculated clock transition point.

Figures

Figures reproduced from arXiv: 2604.24090 by 2, 3), 4, 4), 4) ((1) School of Physics, 5), Alexander M. Jakob (1, Australia), Australia (2) Photon Science Institute, Australia (6) CSIRO Manufacturing, Australia (7) School of Physics, Brett C. Johnson (5), Christopher T.-K. Lew (5), Clayton, Communication Technology (5) Department of Physics, Dane R. McCamey (7), Daniel L. Creedon (6), David N. Jamieson (1, Department of Electrical, Electronic Engineering, Gus O. Bonin (1), Jeffrey C. McCallum (1, London, Manchester, Melbourne, Nicholas Gillespie (1, Parkville, Ravi Acharya (1, Richard J. Curry (2), RMIT University, School of Science, Shao Qi Lim (1, Sydney, United Kingdom (3) London Centre for Nanotechnology, United Kingdom (4) Australian Research Council Centre for Quantum Computation, University College London, University of Manchester, University of Melbourne, University of New South Wales.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) EDMR device schematic, showing the coplanar view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) Calculated energy level diagram of substitutional view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a) Inverse of the peak-to-peak linewidth, 1 view at source ↗
read the original abstract

Magnetic clock transitions (CTs), defined by vanishing first-order sensitivity of the transition frequency to magnetic field fluctuations, provide a powerful route to suppress decoherence in donor spin systems. Here, we present the observation of magnetic field CTs from an ensemble of near-surface $^{75}$As ($I = 3/2$) spins in silicon using low-field ($< 10$~mT) continuous-wave electrically detected magnetic resonance (EDMR). As the CT condition is approached, pronounced linewidth broadening is observed, consistent with a donor Hamiltonian informed linewidth model. These results establish low-field EDMR as a sensitive probe of CTs in near-surface donor systems relevant to silicon-based quantum devices.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript reports the experimental observation of magnetic clock transitions (CTs) for an ensemble of near-surface 75As (I=3/2) donors in silicon, detected via low-field (<10 mT) continuous-wave electrically detected magnetic resonance (EDMR). The central result is a pronounced broadening of the resonance linewidth as the magnetic field is swept toward the CT condition, which the authors state is consistent with a linewidth model informed by the donor spin Hamiltonian. The work concludes that low-field EDMR provides a sensitive probe of CTs in near-surface donor systems relevant to silicon quantum devices.

Significance. If the linewidth broadening can be shown to arise specifically from the vanishing first-order field sensitivity at the CT (rather than competing mechanisms), the result would be significant for silicon-based quantum information processing. It would demonstrate a practical, low-field characterization method for donor CTs in device-like near-surface environments, where surface-induced decoherence is a key concern, and could complement higher-field techniques for validating decoherence-suppression strategies.

major comments (2)
  1. [Results (linewidth vs. field data)] The central claim that the observed linewidth broadening is produced by the CT condition (vanishing first-order field sensitivity) rests on consistency with the donor Hamiltonian linewidth model, but the manuscript provides no explicit exclusion of near-surface artifacts. No control data (e.g., depth-dependent measurements or surface-passivation comparisons) are presented to rule out contributions from interface electric fields, strain gradients, or charge noise that could produce comparable field-dependent broadening.
  2. [Discussion (linewidth model)] The donor Hamiltonian informed linewidth model is invoked to explain the data, yet the text does not specify whether the model is parameter-free, what fixed parameters are taken from literature, or whether any free parameters are fitted to the observed broadening. Without residuals, chi-squared values, or a table of model parameters, it is not possible to assess the uniqueness of the CT attribution.
minor comments (2)
  1. [Abstract] The abstract states the data are 'consistent with' the model but does not report the magnitude of the broadening, the field range over which it occurs, or any uncertainty estimates; adding these quantitative details would strengthen the presentation.
  2. Standard experimental parameters (microwave power, modulation amplitude, temperature, and donor depth distribution) are referenced only qualitatively; a concise methods paragraph or table would improve reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their detailed and constructive report. The two major comments highlight important points about the attribution of the observed linewidth broadening and the transparency of the model. We address each below and indicate the changes planned for the revised manuscript.

read point-by-point responses

  1. Referee: [Results (linewidth vs. field data)] The central claim that the observed linewidth broadening is produced by the CT condition (vanishing first-order field sensitivity) rests on consistency with the donor Hamiltonian linewidth model, but the manuscript provides no explicit exclusion of near-surface artifacts. No control data (e.g., depth-dependent measurements or surface-passivation comparisons) are presented to rule out contributions from interface electric fields, strain gradients, or charge noise that could produce comparable field-dependent broadening.

    Authors: We agree that dedicated control measurements (depth profiling or passivation comparisons) would strengthen the exclusion of near-surface artifacts. Such experiments lie outside the scope of the present study, which focuses on demonstrating low-field EDMR detection of the CTs themselves. However, the broadening we report is not a generic increase but occurs specifically as the applied field is tuned toward the calculated clock-transition condition for the 75As hyperfine manifold; the functional form of the field dependence matches the second-order sensitivity predicted by the donor Hamiltonian. Generic mechanisms such as strain gradients or charge noise would not be expected to produce a resonance-width minimum that tracks the independently calculated CT field. In the revised manuscript we will add a paragraph in the discussion that explicitly compares the expected signatures of interface electric fields and strain against the observed data and the Hamiltonian model. revision: partial

  2. Referee: [Discussion (linewidth model)] The donor Hamiltonian informed linewidth model is invoked to explain the data, yet the text does not specify whether the model is parameter-free, what fixed parameters are taken from literature, or whether any free parameters are fitted to the observed broadening. Without residuals, chi-squared values, or a table of model parameters, it is not possible to assess the uniqueness of the CT attribution.

    Authors: The linewidth model uses the known 75As donor spin Hamiltonian (hyperfine interaction A, nuclear quadrupole interaction, and electron g-factor) with all numerical values taken from established literature; no free parameters are adjusted to fit the observed broadening curve. The model simply computes the second-order field sensitivity at each resonance and converts it to an expected linewidth via the measured inhomogeneous broadening at high field. In the revised manuscript we will (i) add an explicit statement that the calculation is parameter-free with respect to the linewidth data, (ii) include a table of all fixed Hamiltonian parameters together with their literature sources, and (iii) provide a supplementary figure showing the model curve overlaid on the data together with residuals. revision: yes

Circularity Check

0 steps flagged

No significant circularity: experimental observation with external model consistency

full rationale

The paper reports direct experimental observation of magnetic clock transitions via low-field EDMR on near-surface 75As donors, noting linewidth broadening as the CT condition is approached. This is described only as 'consistent with' a donor Hamiltonian informed linewidth model, without any derivation chain, first-principles prediction, or parameter fitting that reduces the observed broadening back to the input data by construction. No self-definitional steps, fitted inputs renamed as predictions, or load-bearing self-citations for uniqueness theorems are present. The central result is an empirical measurement whose interpretation relies on an independent standard donor spin Hamiltonian, making the derivation self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No information available from abstract to identify free parameters, axioms, or invented entities.

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Reference graph

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