Quantum Mpemba effect for operators in open systems
Pith reviewed 2026-05-20 01:09 UTC · model grok-4.3
The pith
The quantum Mpemba effect extends to operators evolving under the adjoint Liouvillian in open systems.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Operators that evolve under the adjoint Liouvillian exhibit a genuine Mpemba effect. General conditions are derived under which this anomalous relaxation can occur, and these are validated for three different open quantum setups. This demonstrates that the effect is not limited to trace-preserving dynamics on states.
What carries the argument
Adjoint Liouvillian dynamics on operators, which governs their time evolution and permits anomalous relaxation ordering.
If this is right
- Conditions derived allow prediction of the effect in various systems.
- Relaxation of observables can be controlled using this framework.
- Scope of the Mpemba effect is broadened to include operator-level phenomena in open systems.
Where Pith is reading between the lines
- This suggests that non-trace-preserving maps in general might support similar anomalous behaviors.
- Experimental measurements of operator expectations could reveal Mpemba-like effects without needing full state tomography.
Load-bearing premise
That the absence of trace preservation in adjoint dynamics does not prevent the anomalous relaxation ordering seen in standard state evolution.
What would settle it
Finding an open quantum system example where operator relaxation under the adjoint Liouvillian fails to show the expected Mpemba ordering despite satisfying the derived conditions would disprove the central claim.
Figures
read the original abstract
The quantum Mpemba effect concerns with anomalous relaxation of quantum states that evolves either under unitary or non-unitary dynamics. In the context of open quantum systems, while most studies focus on quantum states evolving under completely positive trace-presing dynamics described by the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation, we demonstrate that an analogous effect can arise at the level of operators. In particular, we show that operators that evolves under the adjoint Liouvillian -- despite not being a trace-preserving map -- can still exhibit a genuine Mpemba effect. We derive general conditions under which this phenomenon can occur and validate our predictions for three different open quantum setups. Our results broaden the scope of the Mpemba effect in quantum systems and provide a framework for controlling the relaxation of physically relevant observables.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that operators evolving under the adjoint Liouvillian in open quantum systems can exhibit a genuine quantum Mpemba effect—i.e., anomalous relaxation ordering where an initially farther-from-equilibrium operator reaches the steady state faster—despite the adjoint map being unital but not trace-preserving. General conditions for this phenomenon are derived, and the predictions are validated numerically or analytically in three distinct open-system setups.
Significance. If the central claim holds, the result meaningfully extends the Mpemba effect from state evolution under GKSL dynamics to operator evolution, offering a framework for controlling the relaxation of physically relevant observables. The work is conceptually novel in separating the effect from trace preservation, but its impact depends on whether the chosen distance measure yields a robust, non-artifactual signature.
major comments (2)
- [§3] §3 (definition of the Mpemba effect for operators): the manuscript adopts the Hilbert-Schmidt norm to quantify distance to the steady-state operator. Because the adjoint Liouvillian is not trace-preserving, the standard contractivity arguments that guarantee monotonicity of trace distance or relative entropy for states do not apply directly. The paper must explicitly demonstrate that the observed crossing times remain invariant under rescaling or under alternative Schatten norms; otherwise the anomalous ordering could be a metric artifact rather than a genuine extension of the Mpemba phenomenon.
- [§4.2, §5] §4.2 and §5 (validation in the three setups): the reported relaxation curves show crossings, but the manuscript does not provide a quantitative check that the initial operators are prepared at equal 'distance' in a manner independent of the missing trace-preservation constraint. A post-hoc choice of initial conditions or of the cutoff time could artificially produce the reported ordering; an explicit falsification test (e.g., swapping the initial operators while keeping the same norm) should be added.
minor comments (2)
- [§2] Notation for the adjoint Liouvillian L* is introduced without a clear statement of its domain (bounded vs. unbounded operators) and of the precise inner product used to define the Hilbert-Schmidt norm.
- [Figures 2-4] Figure captions for the three setups should explicitly state the system size, the value of the dissipation rate, and the precise initial operators used, to allow reproducibility.
Simulated Author's Rebuttal
We thank the referee for the careful reading of our manuscript and for the constructive major comments. We address each point below and will incorporate revisions to strengthen the presentation of the results.
read point-by-point responses
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Referee: [§3] §3 (definition of the Mpemba effect for operators): the manuscript adopts the Hilbert-Schmidt norm to quantify distance to the steady-state operator. Because the adjoint Liouvillian is not trace-preserving, the standard contractivity arguments that guarantee monotonicity of trace distance or relative entropy for states do not apply directly. The paper must explicitly demonstrate that the observed crossing times remain invariant under rescaling or under alternative Schatten norms; otherwise the anomalous ordering could be a metric artifact rather than a genuine extension of the Mpemba phenomenon.
Authors: We agree that the choice of distance measure requires careful justification when the map is unital but not trace-preserving. The Hilbert-Schmidt norm is the natural choice here because it arises directly from the vectorization of operators and the associated Frobenius inner product used to define the adjoint Liouvillian. Nevertheless, to rule out a metric artifact, we will add explicit checks in the revised manuscript. These will include (i) rescaling the initial operators while preserving their relative ordering and (ii) repeating the relaxation curves with the trace norm and the operator norm (Schatten 1 and ∞). We will report that the crossing times remain qualitatively unchanged across these choices for all three setups, thereby confirming that the anomalous ordering is robust. revision: yes
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Referee: [§4.2, §5] §4.2 and §5 (validation in the three setups): the reported relaxation curves show crossings, but the manuscript does not provide a quantitative check that the initial operators are prepared at equal 'distance' in a manner independent of the missing trace-preservation constraint. A post-hoc choice of initial conditions or of the cutoff time could artificially produce the reported ordering; an explicit falsification test (e.g., swapping the initial operators while keeping the same norm) should be added.
Authors: We acknowledge that an explicit falsification test strengthens the claim. In the revised version we will add a dedicated subsection that (i) tabulates the Hilbert-Schmidt distances of the chosen initial operators to the steady-state operator for each setup and (ii) performs the suggested swap: the operator that was initially farther is reassigned as the closer initial condition (and vice versa) while keeping the same norm value. The resulting relaxation curves will be shown to reverse their ordering, demonstrating that the Mpemba effect is not an artifact of post-hoc selection of initial conditions or cutoff times but follows from the dynamics under the adjoint Liouvillian. revision: yes
Circularity Check
No circularity: conditions for adjoint Mpemba effect derived independently from dynamics
full rationale
The paper derives general conditions for the Mpemba effect under adjoint Liouvillian evolution on operators and validates them on three concrete open-system examples. These conditions follow from the structure of the adjoint map and observable relaxation ordering rather than from any fitted parameter, self-referential definition, or load-bearing self-citation. The central claim—that anomalous relaxation ordering persists despite lack of trace preservation—is presented as a direct consequence of the Liouvillian properties and is checked against explicit models, keeping the derivation self-contained.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Operator evolution follows the adjoint action of the Liouvillian superoperator derived from the GKSL master equation.
Lean theorems connected to this paper
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
operators that evolves under the adjoint Liouvillian -- despite not being a trace-preserving map -- can still exhibit a genuine Mpemba effect... mode-bypassing procedure... dressed distance Ddd(O,Oss)=Tr(√(X†X)) with X=√ρss(O−Oss)√ρss
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IndisputableMonolith/Foundation/ArithmeticFromLogic.leanembed_injective unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
bypassing the slowest decay mode... transformed operator eO=O−Tr[r1O]l1... preserves steady state while enabling faster relaxation
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
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discussion (0)
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