SciPost Submission Page
Near-resonant nuclear spin detection with megahertz mechanical resonators
by Diego Aldo Visani, Letizia Catalini, Christian Lukas Degen, Alexander Eichler, Javier del Pino
Submission summary
| Authors (as registered SciPost users): | Diego Visani |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202508_00046v2 (pdf) |
| Date submitted: | Nov. 14, 2025, 3:45 p.m. |
| Submitted by: | Diego Visani |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Mechanical resonators operating in the megahertz range have become a versatile platform for fundamental and applied quantum research. Their exceptional properties, such as low mass and high quality factor, make them also appealing for force sensing experiments. In this work, we propose a method for detecting, and ultimately controlling, nuclear spins by coupling them to megahertz resonators via a magnetic field gradient. Dynamical backaction between the sensor and an ensemble of N nuclear spins produces a shift in the sensor's resonance frequency. The mean frequency shift due to the Boltzmann polarization is challenging to measure in nanoscale sample volumes. Here, we show that the fluctuating polarization of the spin ensemble results in a measurable increase of the resonator's frequency variance. On the basis of analytical as well as numerical results, we predict that the variance measurement will allow single nuclear spin detection with existing resonator devices.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
We have thoroughly revised the manuscript in response to the detailed comments of Referee 1. In particular, we have clarified the physical origin and magnitude of polarization fluctuations relative to the mean shift, made the role of the fluctuating bath and the relaxation times T1 and T2 more explicit, and improved the presentation of Fig. 1 and the bibliography formatting. Referee 2 was very positive about the work and its relevance, and we have also implemented their suggestions.
A detailed, point-by-point reply to each Referee is provided in the separate response form, where we address all comments and indicate the corresponding changes in the revised manuscript.
We hope that the revised version meets the standards of SciPost Physics and look forward to your assessment.
Sincerely,
Diego A. Visani, Letizia Catalini, Christian L. Degen,
Alexander Eichler, and Javier del Pino
List of changes
- Clarified the relation between polarization fluctuations and mean frequency shift, especially for small spin ensembles and single spins, and explicitly linked this to the main analytical results.
- Made the role of the fluctuating bath and the origin of the stochastic terms in the Langevin equations more explicit, including the meaning of the correlation time and its connection to relaxation processes.
- Added a clearer explanation of the physical origin of the relaxation rates 1/T1 and 1/T2 in nanoscale nuclear spin systems.
- Improved Fig. 1 and its caption to clearly indicate the position of the resonator and spins and their coupling mechanism.
- Revised the bibliography to ensure consistent formatting and capitalization of all titles.
- Adopted a fractional frequency representation for the frequency resolution where appropriate and connected it to relevant experimental work.
- Added a short discussion of the main experimental limitations and challenges to realizing the predicted regimes.
- Polished the manuscript text to improve clarity, structure, and overall presentation in the discussion of physical interpretation and relevance to nanoscale NMR and quantum sensing.
Current status:
Reports on this Submission
Strengths
1- theoretical detailed analysis with message to experiment
Weaknesses
1- quite lengthy
Report
All in all, I can now agree to publication in SciPost Physics.
Still, I find Fig. 1 rather a riddle! Don't worry, I understand what you are showing. But I suggest to add another figure which presents a sketch of a (experimental) setup, e.g. with a cantilever and a driving kind of mechanism so that the reader gets an idea of the discussed apparatus. In your response, you refer to other papers; but your nice work should be self-contained.
Requested changes
see report
Recommendation
Publish (easily meets expectations and criteria for this Journal; among top 50%)