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arxiv: 2511.04310 · v1 · submitted 2025-11-06 · ❄️ cond-mat.mes-hall

Many-body interferometry with semiconductor spins

Daniel Jirovec , Stefano Reale , Pablo Cova-Fari\~na , Christian Ventura-Meinersen , Minh T. P. Nguyen , Xin Zhang , Stefan D. Oosterhout , Giordano Scappucci
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Menno Veldhorst Maximilian Rimbach-Russ Stefano Bosco Lieven M. K. Vandersypen
This is my paper

Pith reviewed 2026-05-18 01:06 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall
keywords semiconductor quantum dotsmany-body interferometryspin spectroscopygermaniumchaotic phasemany-body localizationRamsey interferometry
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The pith

A semiconductor quantum dot array enables full energy spectrum reconstruction of eight interacting spins, showing a localization-to-chaos crossover.

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

The paper shows how to use Ramsey interferometry combined with adiabatic state mapping to measure the energy levels of up to eight spins in a 2 by 4 array of germanium quantum dots. This technique allows reconstruction of the complete spectrum even when spins are interacting strongly. When the interaction energy grows larger than the magnetic disorder, the system begins to display features associated with a chaotic many-body phase rather than remaining localized. A sympathetic reader would care because this demonstrates a scalable way to access complex quantum many-body effects using electrically controlled semiconductor devices that could eventually support quantum simulation tasks.

Core claim

Using a 2x4 array of gate-defined germanium quantum dots, the authors perform spectroscopy on up to eight interacting spins by means of Ramsey interferometry and adiabatic mapping of many-body eigenstates to single-spin eigenstates. This enables complete energy spectrum reconstruction. As the interaction strength exceeds magnetic disorder, signatures of the crossover from a localized to a chaotic phase are observed.

What carries the argument

The adiabatic mapping protocol that converts many-body eigenstates into single-spin eigenstates for readout after Ramsey evolution.

Load-bearing premise

The adiabatic mapping protocol accurately transfers many-body eigenstates onto single-spin eigenstates without significant leakage or diabatic transitions that would distort the reconstructed spectrum.

What would settle it

If experiments with increased interaction strength do not show the predicted changes in energy level statistics or correlations indicating chaos, such as level repulsion, the claim of observing the crossover would be falsified.

Figures

Figures reproduced from arXiv: 2511.04310 by Christian Ventura-Meinersen, Daniel Jirovec, Giordano Scappucci, Lieven M. K. Vandersypen, Maximilian Rimbach-Russ, Menno Veldhorst, Minh T. P. Nguyen, Pablo Cova-Fari\~na, Stefan D. Oosterhout, Stefano Bosco, Stefano Reale, Xin Zhang.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: A we plot the energy levels of a two-spin system as a function of time when pulsing the energy detun￾ing between adjacent dots ϵ as shown. The approximate eigenstates, symbolized by ∼, are also labeled. In the following we omit the ∼, implicitly referring to the ap￾proximate Hamiltonian eigenstates. At t = 0, we initial￾ize |S⟩ at |ϵ| ≫ 0, where both charges reside in the same dot ((2,0) or (0,2) charge co… view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
read the original abstract

Quantum simulators enable studies of many-body phenomena which are intractable with classical hardware. Spins in devices based on semiconductor quantum dots promise precise electrical control and scalability advantages, but accessing many-body phenomena has so far been restricted by challenges in nanofabrication and simultaneous control of multiple interactions. Here, we perform spectroscopy of up to eight interacting spins using a 2x4 array of gate-defined germanium quantum dots. The spectroscopy protocol is based on Ramsey interferometry and adiabatic mapping of many-body eigenstates to single-spin eigenstates, enabling a complete energy spectrum reconstruction. As the interaction strength exceeds magnetic disorder, we observe signatures of the crossover from localization to a chaotic phase marking a step towards the observation of many-body phenomena in quantum dot systems.

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 spectroscopy of up to eight interacting spins in a 2x4 array of gate-defined germanium quantum dots. The protocol combines Ramsey interferometry with adiabatic mapping of many-body eigenstates onto single-spin eigenstates to reconstruct the full energy spectrum. As exchange interaction J exceeds magnetic disorder, the authors report spectral signatures of a crossover from localization to a chaotic phase.

Significance. If the adiabatic mapping remains faithful and the spectral features are robust, the work constitutes a concrete experimental step toward many-body quantum simulation in electrically tunable semiconductor platforms. The demonstration of tunable localization-to-chaos crossover in an eight-spin device is a notable advance over prior few-spin studies in quantum dots.

major comments (2)
  1. [Methods (adiabatic mapping and Ramsey protocol)] The adiabatic mapping protocol is central to the spectrum reconstruction that underpins the localization-to-chaos claim, yet the manuscript provides no explicit fidelity benchmarks, Landau-Zener estimates, or time-dependent simulations for the 8-spin case at the ramp times and interaction strengths used. Without these, residual diabatic leakage cannot be ruled out as a source of apparent level broadening or mixing.
  2. [Results (spectral reconstruction and crossover analysis)] The reported crossover signatures rest on the reconstructed spectra, but the text does not detail post-selection criteria, calibration stability, or quantitative error bars on the extracted level statistics. This omission leaves open whether the observed broadening is robust against experimental choices.
minor comments (2)
  1. [Figure captions] Figure captions should explicitly state the number of experimental repetitions and the fitting procedure used to extract the many-body energies.
  2. [Notation and definitions] Notation for the disorder strength and interaction parameter J should be defined consistently in the main text and supplementary material.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our work and for the constructive comments, which help clarify the presentation of our methods and results. We address each major comment below and will incorporate revisions to strengthen the manuscript.

read point-by-point responses

  1. Referee: [Methods (adiabatic mapping and Ramsey protocol)] The adiabatic mapping protocol is central to the spectrum reconstruction that underpins the localization-to-chaos claim, yet the manuscript provides no explicit fidelity benchmarks, Landau-Zener estimates, or time-dependent simulations for the 8-spin case at the ramp times and interaction strengths used. Without these, residual diabatic leakage cannot be ruled out as a source of apparent level broadening or mixing.

    Authors: We agree that explicit validation of the adiabatic mapping is important for the 8-spin case. Although supporting estimates were performed during analysis, they were omitted from the original submission for brevity. In the revised manuscript we will add Landau-Zener transition probability calculations for the relevant ramp times and interaction strengths, together with time-dependent simulations of the full 8-spin Hamiltonian to quantify residual diabatic leakage and confirm that it does not account for the observed spectral features. revision: yes

  2. Referee: [Results (spectral reconstruction and crossover analysis)] The reported crossover signatures rest on the reconstructed spectra, but the text does not detail post-selection criteria, calibration stability, or quantitative error bars on the extracted level statistics. This omission leaves open whether the observed broadening is robust against experimental choices.

    Authors: We acknowledge that additional details on data processing are needed. The revised version will include a clear description of the post-selection criteria applied to the Ramsey data, a summary of calibration stability across the measurement runs, and quantitative error bars or uncertainty estimates on the extracted level spacings and statistics used to identify the localization-to-chaos crossover. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental spectrum reconstruction rests on measured data

full rationale

The paper is an experimental work that performs spectroscopy on up to eight spins in a germanium quantum-dot array using Ramsey interferometry combined with adiabatic mapping to reconstruct the many-body energy spectrum. The central claim of observing a localization-to-chaos crossover when interaction exceeds magnetic disorder is drawn directly from the measured spectra rather than from any theoretical derivation, prediction, or first-principles calculation that reduces to its own inputs by construction. No self-definitional steps, fitted inputs renamed as predictions, or load-bearing self-citations appear in the protocol description or results. The reconstruction method is presented as a measurement technique whose validity is assessed against the experimental outcomes themselves, making the work self-contained against external benchmarks with no reduction of claimed results to tautological inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

The central claim rests on the experimental platform and mapping protocol rather than new theoretical axioms or invented particles; no free parameters or invented entities are introduced in the abstract.

pith-pipeline@v0.9.0 · 5707 in / 1017 out tokens · 27723 ms · 2026-05-18T01:06:26.099138+00:00 · methodology

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Forward citations

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Reference graph

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    ADDITIONAL SPIN CHAINS We report other measured spin chains in Fig. S13. Specifically, we show data for a chain formed by dots 2-1-5-6 (Fig. S13A), chain 3-4-8-7 (Fig. S13C), and another instance of the full eight-spin chain (Fig. S13E). The gray lines represent the modeled frequencies. Figures S13B, D, and F report the effective exchanges applied as extr...

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  73. [73]

    DISCUSSION ON ADIABA TIC RAMPS FIG. S14. FFT of oscillations for the 8-spin chain reported in Fig. 4 measured at different ramp timesτ ramp initializing and reading-out dot 7 and 8 respectively. The data where normalized at the maximum signal among all the spectra in order to compare the FFT intensities. To ensure adiabatic ramps to the interacting regime...

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  74. [74]

    S16.AFrequencies as extracted from model Hamiltonian with experimentally fitted parameters (Fig

    SIMULA TED SPECTRAL FORM F ACTOR 0 5 10 15 20 25 30 35 Energy Level index 7.5 5.0 2.5 0.0 2.5 5.0 7.5 Exp-Theo (MHz) J/E Z = 0 J/E Z = 1 J/E Z = 2 J/E Z = 0 J/E Z = 1 J/E Z = 2 0 5 10 15 20 25 30 35 Energy Level index 0 2 4 6 8 10 12 14Error (%) A B C D EZJ/=0, 1, 2 EZJ/ 0 1 2 0 20 40 60 80 100 120f (MHz) 10 9 10 8 10 7 10 6 10 5 Time (t) 10 4 10 3 10 2 1...

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