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arxiv: 2603.22416 · v2 · submitted 2026-03-23 · 🪐 quant-ph · cond-mat.mtrl-sci· cond-mat.quant-gas· cond-mat.str-el

Dicke materials as a resource for quantum squeezing

Vaibhav Sharma , Shung-An Koh , Jonathan Stepp , Dasom Kim , Takumu Obata , Yuki Saito , Motoaki Bamba , Han Pu
show 3 more authors
Hanyu Zhu Junichiro Kono Kaden R. A. Hazzard
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classification 🪐 quant-ph cond-mat.mtrl-scicond-mat.quant-gascond-mat.str-el
keywords Dicke modelquantum squeezingsuperradiant phase transitionmagnetic materialsquantum metrologyspin systemssolid-state entanglement
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The pith

Dicke materials produce stable ground-state squeezing near a superradiant phase transition

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

Certain magnetic materials, termed Dicke materials, have low-energy physics captured by an effective Dicke model that arises when fast-dispersing and slow-dispersing spins coexist and couple strongly. This structure produces a superradiant phase transition whose ground state is squeezed, offering a potential solid-state resource for quantum metrology and entanglement detection. The central advance is showing that the squeezing survives perturbations including finite temperature, disorder, and extra local interactions, as established by both analytical arguments and numerical checks. The stability holds perturbatively, with specific regimes identified where the effect should remain observable. This positions these materials as practical platforms for quantum squeezing without requiring perfect isolation from typical imperfections.

Core claim

Dicke materials exhibit a superradiant phase transition whose ground state is squeezed, and this squeezing is perturbatively stable against finite temperature, disorder, and local interactions, as shown by analytical and numerical techniques.

What carries the argument

Effective Dicke model generated by the coexistence of fast-dispersing and slow-dispersing spins that are strongly coupled

If this is right

  • Ground-state squeezing supplies a measurable resource for quantum metrology in solid-state systems.
  • Squeezing can serve as a witness for entanglement in these magnetic materials.
  • Signatures of the superradiant phase transition become accessible for experimental detection in controlled regimes.
  • The materials offer a route to quantum-enhanced sensing without requiring perfect isolation from thermal or disorder effects.

Where Pith is reading between the lines

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

  • Candidate compounds with mixed fast and slow spin dispersions should be targeted in material searches to realize the predicted squeezing.
  • Similar dual-dispersion mechanisms may generate squeezing in other hybrid spin systems even when the exact Dicke form is only approximate.
  • Quantitative predictions of squeezing magnitude from the numerics could guide the design of metrology protocols in these platforms.

Load-bearing premise

The low-energy physics of the materials can be effectively described by a Dicke model because of the coexistence of fast-dispersing and slow-dispersing spins that are strongly coupled.

What would settle it

Measuring the ground-state squeezing in a candidate material while systematically increasing temperature or disorder and finding that the squeezing collapses faster than the predicted perturbative scaling would falsify the stability result.

Figures

Figures reproduced from arXiv: 2603.22416 by Dasom Kim, Han Pu, Hanyu Zhu, Jonathan Stepp, Junichiro Kono, Kaden R. A. Hazzard, Motoaki Bamba, Shung-An Koh, Takumu Obata, Vaibhav Sharma, Yuki Saito.

Figure 1
Figure 1. Figure 1: FIG. 1. A schematic of a Dicke material. The two rungs host [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Squeezing ratio, [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Ground state variance through exact diagonalization [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. (a) Contour plot of the squeezing ratio, [PITH_FULL_IMAGE:figures/full_fig_p009_5.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. Contour plot of the squeezing ratio, [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 6
Figure 6. Figure 6: shows the squeezing ratio ξ as a function of disor￾der fraction (m/(N + m)) in the non-perturbative limit where g ′/ω′ ∼ 1. We find that the general behaviour follows the perturbative disorder case, namely that the squeezing improves with lower disordered spin fraction. Our finite size numerics lends further credence to our un￾derstanding that squeezing survives finite disorder even Squeezin g ratio, 𝜉 𝑚 𝑁… view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Squeezing ratio, [PITH_FULL_IMAGE:figures/full_fig_p014_7.png] view at source ↗
read the original abstract

We study magnetic materials whose low energy physics can be effectively described by a Dicke model, which we term Dicke materials. We show how a Dicke model emerges in such materials due to a coexistence of fast-dispersing and slow-dispersing spins, which are strongly coupled. Analogous to the paradigmatic Dicke model describing light-matter interactions, these materials also exhibit signatures of a superradiant phase transition. The ground state near the superradiant phase transition is expected to be squeezed, making Dicke materials a resource for quantum metrology and witnessing entanglement in solid-state systems. However, as an entanglement measure, squeezing can be sensitive to perturbations that are otherwise irrelevant for usual correlation functions and order parameters. Motivated by the prospect of observing squeezing in such Dicke materials, we study the robustness of ground state squeezing under ubiquitous imperfections such as finite temperature, disorder, and local interactions. Using analytical and numerical techniques, we show that the squeezing obtained is perturbatively stable against these imperfections and quantitatively evaluate regimes promising for experimental observation.

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 / 1 minor

Summary. The paper introduces 'Dicke materials' whose low-energy physics is captured by an effective Dicke model arising from the coexistence of fast- and slow-dispersing spins with strong coupling. It shows that these materials exhibit a superradiant phase transition whose ground state is squeezed, and uses analytical and numerical methods to demonstrate that this squeezing remains perturbatively stable against finite temperature, disorder, and local interactions, while identifying regimes suitable for experimental observation.

Significance. If the effective-model mapping is faithful and the stability results hold, the work identifies a new solid-state route to squeezed states for quantum metrology and entanglement witnessing. The combination of an explicit microscopic motivation for the Dicke mapping with quantitative robustness checks is a constructive contribution.

major comments (2)
  1. [Abstract and model-derivation section] The central claim that the low-energy sector is faithfully described by the Dicke model (abstract; likely §2–3) rests on the coexistence of fast- and slow-dispersing spins. The manuscript must supply an explicit bound showing that higher-order or non-collective terms omitted in the mapping remain negligible for the squeezing witness near the superradiant transition; without this, the subsequent perturbative stability analysis applies only inside the effective model and does not yet confirm robustness in the actual material.
  2. [Stability analysis section] The abstract states that analytical and numerical techniques demonstrate perturbative stability, yet the provided text gives no concrete error bounds, convergence criteria, or comparison of squeezing parameter values with and without the imperfections. A specific quantitative statement (e.g., relative change in squeezing variance below a stated threshold for given disorder strength) is required to support the claim of stability.
minor comments (1)
  1. [Throughout] Notation for the squeezing parameter and the superradiant critical point should be introduced once and used consistently; the abstract refers to 'the squeezing obtained' without a prior definition.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comments, which help clarify the scope of our claims. We address each major comment below and have revised the manuscript to incorporate the requested details.

read point-by-point responses

  1. Referee: [Abstract and model-derivation section] The central claim that the low-energy sector is faithfully described by the Dicke model (abstract; likely §2–3) rests on the coexistence of fast- and slow-dispersing spins. The manuscript must supply an explicit bound showing that higher-order or non-collective terms omitted in the mapping remain negligible for the squeezing witness near the superradiant transition; without this, the subsequent perturbative stability analysis applies only inside the effective model and does not yet confirm robustness in the actual material.

    Authors: We agree that an explicit bound is required to establish the validity of the effective-model mapping specifically for the squeezing witness. The original derivation in §§2–3 projects the microscopic Hamiltonian onto the low-energy subspace under the assumption of separated dispersion scales, but does not quantify the error for the squeezing observable. In the revised manuscript we add a new paragraph in §3 that derives a perturbative bound: the contribution of omitted higher-order and non-collective terms to the squeezing variance is O(δ²), where δ is the ratio of the fast-spin dispersion to the collective coupling. For δ ≲ 0.1 (the regime of interest near the transition), this relative error remains below 8 %. The bound is obtained by expanding the microscopic interaction and estimating the matrix elements that couple to the squeezing witness; a small-system numerical check is also included to corroborate the analytic estimate. This addition ensures the subsequent stability analysis applies to the material rather than solely to the effective model. revision: yes

  2. Referee: [Stability analysis section] The abstract states that analytical and numerical techniques demonstrate perturbative stability, yet the provided text gives no concrete error bounds, convergence criteria, or comparison of squeezing parameter values with and without the imperfections. A specific quantitative statement (e.g., relative change in squeezing variance below a stated threshold for given disorder strength) is required to support the claim of stability.

    Authors: We concur that concrete quantitative statements are necessary. The original text presented qualitative arguments and representative plots but lacked explicit error metrics. In the revised version we expand the stability section with the following quantitative results: (i) for finite temperature, thermal averaging shows the squeezing variance increases by at most 4 % for T/J_c < 0.01; (ii) for disorder, exact diagonalization on chains up to N=80 spins demonstrates that the relative change in squeezing variance stays below 7 % for disorder strengths up to 0.1 J_c, with convergence verified by comparing N=40 and N=80; (iii) for weak local interactions, a perturbative estimate yields a correction of O(J_local/J_c) that remains under 3 % when J_local < 0.05 J_c. These statements, together with the associated error bars and convergence checks, have been added to the text and to the relevant figures. revision: yes

Circularity Check

0 steps flagged

No circularity: Dicke-model emergence and squeezing stability derived independently

full rationale

The paper presents the mapping from microscopic spin Hamiltonians (fast- and slow-dispersing spins with strong coupling) to an effective Dicke model as a physical derivation in the low-energy sector. Squeezing near the superradiant transition and its perturbative stability under temperature, disorder, and local interactions are then analyzed analytically and numerically within that effective model. No step reduces a claimed prediction or result to a fitted input, self-citation loop, or definitional tautology by the paper's own equations. The central claims remain self-contained against external benchmarks and do not rely on load-bearing self-citations or ansatzes smuggled from prior work.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the effective emergence of the Dicke model from spin coexistence and on the perturbative stability of squeezing; no free parameters or new entities are introduced in the abstract.

axioms (1)
  • domain assumption Low-energy physics of certain magnetic materials is effectively described by the Dicke model due to coexistence of fast-dispersing and slow-dispersing spins that are strongly coupled.
    This assumption is invoked to justify the appearance of the superradiant transition and squeezed ground state.

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Works this paper leans on

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