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arxiv: 2605.09878 · v1 · submitted 2026-05-11 · 🪐 quant-ph · cond-mat.stat-mech

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Clifford Ergotropy

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Pith reviewed 2026-05-12 04:59 UTC · model grok-4.3

classification 🪐 quant-ph cond-mat.stat-mech
keywords Clifford ergotropyquantum magicstabilizer Rényi entropyquantum thermodynamicsClifford operationsresource theorymany-body systemssecond law
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The pith

Clifford ergotropy is bounded above by a quantity that decreases as the quantum magic of the state increases.

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

The paper defines Clifford ergotropy as the maximum energy extractable from a quantum state when only Clifford operations are allowed. It derives universal upper bounds on this quantity expressed through the infinite-order filtered stabilizer Rényi entropy, so that greater magic tightens the bound and reduces possible extraction. A reader would care because Clifford operations are efficient and physically realizable, turning the result into a concrete limit on work extraction in any process restricted to those operations. The bounds are demonstrated explicitly for one- and two-qubit cases and then used to obtain a form of the second law that holds for typical many-body states under the same restriction.

Core claim

Clifford ergotropy, the extractable energy under the restriction to Clifford operations, admits universal upper bounds that decrease with increasing magic as quantified by the infinite-order filtered stabilizer Rényi entropy. These bounds are illustrated for one- and two-qubit systems, where the two-qubit case exhibits a transition in the control landscape, and they imply a second law of thermodynamics under Clifford operations for typical states in many-body systems.

What carries the argument

The universal upper bound that directly relates Clifford ergotropy to the infinite-order filtered stabilizer Rényi entropy, which quantifies magic and thereby limits extractable energy.

If this is right

  • The bound is tight enough to be useful for one- and two-qubit systems and reveals a transition in the two-qubit Clifford control landscape.
  • Typical many-body states obey a second law of thermodynamics when energy extraction is restricted to Clifford operations.
  • The upper bounds hold universally and become stricter as the state's magic, measured by the infinite-order filtered stabilizer Rényi entropy, increases.
  • The analysis connects resource-theoretic magic directly to thermodynamic extractability under efficient gate restrictions.

Where Pith is reading between the lines

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

  • In any quantum device limited to Clifford gates, extra magic resources would be required to reach the highest possible energy extraction in a thermodynamic process.
  • The same bounding technique could be adapted to other restricted gate sets that arise in near-term hardware, yielding analogous thermodynamic limits.
  • Numerical checks on small simulators could directly test whether the predicted transition in the two-qubit control landscape appears in physical devices.

Load-bearing premise

That restricting allowed operations to the Clifford group captures the thermodynamic cost of magic and that the filtered stabilizer Rényi entropy is the appropriate quantifier of that cost for systems of every size.

What would settle it

A calculation or measurement on any two-qubit state in which the actual Clifford ergotropy exceeds the numerical value of the upper bound supplied by its infinite-order filtered stabilizer Rényi entropy.

Figures

Figures reproduced from arXiv: 2605.09878 by Ryusuke Hamazaki, Somnath Maity.

Figure 1
Figure 1. Figure 1: FIG. 1. Comparison between the ergotropy [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
read the original abstract

We discuss the interplay between thermodynamics and magic resources in closed quantum dynamics by introducing Clifford ergotropy, the amount of extractable energy under the restriction to Clifford operations. We provide universal upper bounds on Clifford ergotropy, which decrease with increasing magic as quantified by the infinite-order filtered stabilizer R\'enyi entropy. We demonstrate the utility of this bound for one- and two-qubit systems, with the latter exhibiting a notable transition in the control landscape of Clifford ergotropy. Finally, we show that our analysis has nontrivial consequences even for many-body systems, including a form of the second law of thermodynamics under Clifford operations for typical quantum states.

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 paper introduces Clifford ergotropy as the maximum energy extractable from a quantum state via Clifford unitaries alone. It derives universal upper bounds on this quantity that decrease monotonically with the infinite-order filtered stabilizer Rényi entropy (a magic monotone), demonstrates the bounds and a control-landscape transition for one- and two-qubit systems, and extends the analysis to many-body systems to obtain a form of the second law that holds for typical states under Clifford-restricted dynamics.

Significance. If the universal bounds and the many-body second-law statement are rigorously established, the work supplies a concrete resource-theoretic link between magic and thermodynamic work extraction under a computationally relevant restriction (Clifford operations). The explicit small-system calculations and the observation that the bound tightens with magic provide falsifiable predictions that could be tested in near-term devices; the many-body extension, if free of hidden assumptions on the Hamiltonian spectrum, would be a notable addition to the literature on restricted-operation thermodynamics.

major comments (2)
  1. [Abstract / §3] Abstract and the derivation of the universal bound (presumably §3): the claim that the upper bound on Clifford ergotropy is independent of the specific eigenvalues of H and holds for arbitrary many-body Hamiltonians is load-bearing for the universality statement. The skeptic correctly notes that Clifford orbits may not sample the spectrum uniformly unless the Hamiltonian commutes with the Clifford group action or its eigenspaces are Clifford-invariant; the manuscript must explicitly state the spectral assumption (or prove independence) rather than relying on the post-Clifford energy evaluation alone.
  2. [§4 / many-body section] Two-qubit transition and many-body extension: the reported change in optimal Clifford control with increasing magic is interesting, but the manuscript must show that the same magic-monotone bound continues to upper-bound the extractable work when the system size grows and the Hamiltonian is generic (e.g., a random Ising model). Without an explicit check that the filtered Rényi entropy still controls the overlap with the Clifford orbit for non-stabilizer initial states, the many-body second-law claim risks being limited to Hamiltonians whose spectrum aligns with stabilizer subspaces.
minor comments (2)
  1. Notation: the infinite-order filtered stabilizer Rényi entropy is introduced without a compact symbol; adopting a short notation (e.g., M_∞) would improve readability when the bound is stated repeatedly.
  2. [Abstract] The abstract states that the bounds 'decrease with increasing magic'; the manuscript should include a short remark clarifying whether the inequality is strict or non-increasing, and whether equality cases are characterized.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive suggestions. We address the two major comments below and will revise the manuscript accordingly to strengthen the presentation of the universal bound and the many-body extension.

read point-by-point responses
  1. Referee: [Abstract / §3] Abstract and the derivation of the universal bound (presumably §3): the claim that the upper bound on Clifford ergotropy is independent of the specific eigenvalues of H and holds for arbitrary many-body Hamiltonians is load-bearing for the universality statement. The skeptic correctly notes that Clifford orbits may not sample the spectrum uniformly unless the Hamiltonian commutes with the Clifford group action or its eigenspaces are Clifford-invariant; the manuscript must explicitly state the spectral assumption (or prove independence) rather than relying on the post-Clifford energy evaluation alone.

    Authors: We agree that an explicit statement of the spectral assumption is needed for rigor. The bound is derived from the fact that the infinite-order filtered stabilizer Rényi entropy constrains the maximum overlap between a state and any Clifford orbit, which in turn limits the achievable energy difference after a Clifford unitary; this difference is then evaluated with respect to the eigenvalues of H. Because the entropy bound is independent of H, the resulting upper bound on Clifford ergotropy inherits that independence provided the Clifford group acts sufficiently ergodically on the energy eigenspaces. We will add a clarifying paragraph in §3 that states this assumption explicitly (namely, that either H commutes with the Clifford action or its spectrum is sufficiently non-degenerate that the orbit samples the eigenvalues uniformly) and note that the bound remains valid for any H satisfying this condition. This addresses the concern without altering the derivation. revision: yes

  2. Referee: [§4 / many-body section] Two-qubit transition and many-body extension: the reported change in optimal Clifford control with increasing magic is interesting, but the manuscript must show that the same magic-monotone bound continues to upper-bound the extractable work when the system size grows and the Hamiltonian is generic (e.g., a random Ising model). Without an explicit check that the filtered Rényi entropy still controls the overlap with the Clifford orbit for non-stabilizer initial states, the many-body second-law claim risks being limited to Hamiltonians whose spectrum aligns with stabilizer subspaces.

    Authors: The many-body second-law statement is formulated for typical (Haar-random or high-entropy) initial states, for which the filtered stabilizer Rényi entropy directly bounds the distance to the nearest stabilizer state and hence the maximum overlap with any Clifford orbit. Because typical states have energy distributions that concentrate around the mean for generic local Hamiltonians (including random Ising models), the Clifford-restricted work extraction is controlled by the same monotone irrespective of the precise spectrum. We will expand the discussion in §4 to include a short argument showing that the bound carries over to generic many-body Hamiltonians via this typicality, without requiring stabilizer-subspace alignment. While a full numerical survey for large random Ising instances lies beyond the present scope, the analytic typicality argument suffices to support the claim for the class of states considered. revision: partial

Circularity Check

0 steps flagged

No significant circularity; bounds derived from definitions without reduction to inputs.

full rationale

The paper introduces Clifford ergotropy directly from the restriction to Clifford unitaries and derives universal upper bounds using the infinite-order filtered stabilizer Rényi entropy as a magic quantifier. These steps follow from the operational definitions and standard properties of Clifford orbits and stabilizer polytopes, without fitting parameters to data subsets, self-citation chains that bear the central claim, or renaming known results as new derivations. The many-body second-law consequence is presented as a consequence for typical states, remaining independent of the specific Hamiltonian spectrum in the stated universality. No load-bearing step reduces by construction to its own inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 1 invented entities

The central claims rest on the newly introduced definition of Clifford ergotropy and the choice of the infinite-order filtered stabilizer Rényi entropy as the magic quantifier; these are domain assumptions standard in quantum resource theories but not independently verified here.

axioms (2)
  • domain assumption Clifford operations form the relevant restricted set of unitaries for thermodynamic work extraction
    The paper defines Clifford ergotropy by restricting to this gate set by construction.
  • domain assumption The infinite-order filtered stabilizer Rényi entropy quantifies the relevant magic resource for energy extraction
    The bounds are stated to decrease with this specific entropy measure.
invented entities (1)
  • Clifford ergotropy no independent evidence
    purpose: Quantify maximum extractable energy under Clifford restriction
    Newly defined quantity whose properties are derived in the paper.

pith-pipeline@v0.9.0 · 5395 in / 1416 out tokens · 49763 ms · 2026-05-12T04:59:31.159762+00:00 · methodology

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Reference graph

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