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arxiv: 2605.07124 · v1 · submitted 2026-05-08 · 🪐 quant-ph

Nonselective generalized measurements as a resource for quantum thermal machines in a double quantum dot

Bruno Carvalho , Jonas F. G. Santos , Moises Rojas This is my paper

Pith reviewed 2026-05-11 01:05 UTC · model grok-4.3

classification 🪐 quant-ph
keywords quantum thermal machinesgeneralized measurementsdouble quantum dotinterdot tunnelingrefrigerationmeasurement-driven thermodynamicsquantum thermodynamicsheat engine
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The pith

Coherent interdot tunneling in a double quantum dot generates refrigeration modes in measurement-driven thermal machines that are absent without it.

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

The paper examines a double quantum dot with coherent tunneling as the working substance for a quantum thermal machine driven by nonselective generalized measurements. It defines a three-stroke cycle of thermalization with one reservoir followed by two measurement channels, then derives the energy and entropy changes to map the resulting operational regimes. The central result is that tunneling hybridizes the localized states and shifts the boundaries between heat-engine, accelerator, heater, and refrigerator modes, specifically opening refrigeration configurations impossible in the purely detuned case. A reader would care because the work shows how a controllable coherent coupling can expand the functionality of measurement-powered devices in a platform already accessible to experiment.

Core claim

In the double quantum dot, competition between detuning and tunneling modifies the energetic response during the cycle of single-reservoir thermalization and two generalized measurements. Depending on the measurement parameters, the device operates as a heat engine, accelerator, heater, or refrigerator. Tunneling reshapes the mode boundaries and produces refrigeration regimes that do not exist in the detuned qubit limit, while temperature, detuning, and tunneling amplitude together determine the regions of optimal work extraction and cooling.

What carries the argument

The three-stroke cycle of thermalization with a single reservoir plus two nonselective generalized measurement channels, acting on the hybridized states produced by interdot tunneling.

If this is right

  • Refrigeration becomes accessible in ranges of detuning and measurement strength forbidden by the detuned model alone.
  • The boundaries separating engine, accelerator, heater, and refrigerator operation shift continuously with tunneling amplitude.
  • Optimal performance for work extraction and cooling is jointly controlled by temperature, detuning, and tunneling strength.
  • Double quantum dots offer an experimentally relevant setting for implementing measurement-assisted thermodynamic devices.

Where Pith is reading between the lines

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

  • Varying the interdot tunneling in solid-state quantum-dot experiments could switch the machine between modes on demand.
  • The same hybridization mechanism might be exploited in other coherent two-level systems to design measurement-driven coolers with a single bath.
  • Because only one thermal reservoir is required, the architecture could reduce the hardware overhead for autonomous quantum thermodynamic tasks.

Load-bearing premise

The three-stroke cycle of thermalization and two measurements fully captures the thermodynamics without additional decoherence or reservoir coupling during the measurement steps.

What would settle it

Direct measurement of heat flows or coefficient of performance in a double quantum dot while sweeping tunneling amplitude, to check whether refrigeration appears only in the parameter regions predicted when tunneling is present.

Figures

Figures reproduced from arXiv: 2605.07124 by Bruno Carvalho, Jonas F. G. Santos, Moises Rojas.

Figure 1
Figure 1. Figure 1: Schematic cycle in the S–⟨U⟩ plane for the measurement-driven machine. B. Internal energy and entropy variation in a measurement-driven machine To characterize the heat and work in a machine driven by generalized (non-selective) measurements, we derive the energy and entropy changes induced along the cycle. In this framework, the von Neumann entropy and the internal energy of a state ρ (i) are defined as S… view at source ↗
Figure 2
Figure 2. Figure 2: Schematic cycles in the S–⟨U⟩ plane for the measurement-driven machine, showing the three possible or￾derings of the measurement-induced strokes. optimal operation (with COP = 1 yielding κ = 0.5). This normalization provides a unified bounded scale to compare all operational modes. IV. QUANTUM OPERATIONAL REGIMES In this section, we analyze the operational regimes of the measurement-driven quantum thermal … view at source ↗
Figure 3
Figure 3. Figure 3: The operational modes of the quantum cycle as a function of [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Performance of the quantum machine based on generalized measurement as a function of [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: The operational modes of the quantum cycle as a function of [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Performance of the measurement-driven quantum machine in the [PITH_FULL_IMAGE:figures/full_fig_p006_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Schematic refrigeration cycles in the S–⟨U⟩ plane. Depending on the ordering of Ma , Mb , and thermalization, the cycle realizes different refrigeration-related trajectories. competition between heater and accelerator operation for a < 0.5. The white region corresponds to parameter for which the exchanged heat and work do not satisfy the sign conditions required for any well-defined operational mode. In th… view at source ↗
Figure 8
Figure 8. Figure 8: Operational modes of the quantum cycle driven by generalized measurements as a function of [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Performance of the measurement-driven quantum machine in the [PITH_FULL_IMAGE:figures/full_fig_p008_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: The operational modes of the quantum cycle as a function of [PITH_FULL_IMAGE:figures/full_fig_p010_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: Thermal efficiency of the quantum cycle as a function of [PITH_FULL_IMAGE:figures/full_fig_p011_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: The operational modes of the quantum cycle as a function of [PITH_FULL_IMAGE:figures/full_fig_p012_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Thermal efficiency of the quantum cycle as a function of [PITH_FULL_IMAGE:figures/full_fig_p013_13.png] view at source ↗
read the original abstract

We investigated quantum thermal machines powered by sequential nonselective generalized measurements, taking a double quantum dot with coherent interdot tunneling as a working substance. In this platform, the competition between detuning and tunneling hybridizes the localized states and modifies the energetic response of the cycle, allowing us to analyze measurement-driven thermodynamics beyond simple diagonal qubit models. We formulate a three-stroke cycle composed of thermalization with a single reservoir and two generalized measurement channels, and derive the corresponding internal-energy and entropy variations in order to identify the operational regimes of the device. Depending on the measurement parameters, the system can operate as a heat engine, accelerator, heater, or refrigerator. We show that the introduction of tunneling not only reshapes the boundaries between these modes, but also generates refrigeration configurations that are absent in the purely detuned model. In addition, the performance maps reveal that temperature, detuning, and tunneling amplitude jointly control the most favorable regions for work extraction and cooling. Our results demonstrate that coherent interdot coupling acts as an important resource for optimizing measurement-powered quantum thermal machines and highlight double quantum dots as a promising setting for experimentally relevant implementations of measurement-assisted thermodynamic devices.

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

1 major / 2 minor

Summary. The manuscript studies measurement-driven quantum thermal machines using a double quantum dot with coherent interdot tunneling as the working substance. It defines a three-stroke cycle (thermalization with one reservoir plus two nonselective generalized measurements), derives the associated internal-energy and entropy variations, and maps the resulting operational regimes (heat engine, accelerator, heater, refrigerator) in the space of detuning, tunneling amplitude, temperature, and measurement strength. The central result is that finite tunneling hybridizes the states, reshapes regime boundaries, and produces refrigeration configurations that do not appear in the purely detuned (t=0) limit.

Significance. If the derivations hold under the stated idealizations, the work shows that coherent interdot coupling functions as a tunable resource that enlarges the accessible thermodynamic operating space beyond simple diagonal qubit models. The explicit performance maps in the multi-parameter space supply concrete, experimentally relevant predictions for double-dot platforms, which are already accessible in the laboratory.

major comments (1)
  1. [§II] §II (three-stroke cycle definition): the derivation assumes that each generalized measurement channel acts instantaneously on the hybridized eigenstates with no additional Lindblad-type reservoir coupling or dephasing during the measurement strokes. Because hybridization mixes the localized states, any finite-duration or weak-lead effect would generate extra entropy production that is larger for t>0 than for t=0; this term is absent from the reported energy and entropy balances and could close the refrigeration windows that appear only at finite tunneling.
minor comments (2)
  1. [Abstract] The abstract states that internal-energy and entropy variations are derived but does not display the resulting expressions; including the key formulas (or their section references) would improve immediate readability.
  2. [§III] Notation for the measurement operators and the hybridization parameter could be collected in a single table for quick reference when reading the regime maps.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the positive overall assessment. The single major comment concerns the modeling assumptions in the three-stroke cycle; we address it point by point below.

read point-by-point responses

  1. Referee: [§II] §II (three-stroke cycle definition): the derivation assumes that each generalized measurement channel acts instantaneously on the hybridized eigenstates with no additional Lindblad-type reservoir coupling or dephasing during the measurement strokes. Because hybridization mixes the localized states, any finite-duration or weak-lead effect would generate extra entropy production that is larger for t>0 than for t=0; this term is absent from the reported energy and entropy balances and could close the refrigeration windows that appear only at finite tunneling.

    Authors: We agree that the derivations rest on the idealization of instantaneous generalized measurements applied directly to the hybridized eigenstates, with no concurrent reservoir coupling or dephasing during those strokes. This is a standard modeling choice in the literature on measurement-driven quantum thermodynamics, chosen to isolate the thermodynamic role of the nonselective measurements on the coherently coupled double-dot system. Within this limit the energy and entropy balances are exact, and the new refrigeration regimes arise from the tunneling-induced hybridization that alters the eigenenergies and the action of the measurement operators. The referee is correct that a finite-duration measurement would require an additional time-dependent Lindblad term whose entropy production would be larger at finite t; such an extension lies outside the present scope and could indeed narrow or close some of the reported windows. We will therefore revise Section II to state the instantaneous approximation explicitly, to note its limitations, and to indicate how a finite-time model could be constructed in future work. This addition will not change the reported results but will clarify the regime of validity. revision: partial

Circularity Check

0 steps flagged

No circularity: derivations follow directly from model definitions without reduction to inputs

full rationale

The paper defines the double-dot Hamiltonian with detuning and tunneling, specifies the three-stroke cycle (thermalization plus two nonselective generalized measurements), and derives internal-energy and entropy changes from the resulting density-matrix evolution and measurement operators. These steps are self-contained within the stated assumptions and do not invoke fitted parameters renamed as predictions, self-citations as load-bearing uniqueness theorems, or ansatzes smuggled from prior work. The comparison between finite-tunneling and t=0 cases is performed inside the same derived expressions, yielding the reported refrigeration regimes as a direct consequence rather than a circular restatement of the inputs.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 0 invented entities

The central claim rests on a standard open-quantum-system description of thermalization and nonselective measurements plus the specific three-stroke cycle structure; no new physical entities are postulated.

free parameters (3)
  • measurement parameters
    Parameters defining the generalized measurement channels that control energy and entropy changes.
  • detuning
    Energy difference between the two dots.
  • tunneling amplitude
    Strength of coherent interdot coupling.
axioms (2)
  • standard math Standard quantum mechanics for open systems and generalized measurements
    Invoked to describe thermalization and nonselective measurement effects on the hybridized states.
  • domain assumption Three-stroke cycle model with single reservoir
    The thermodynamic cycle is defined as thermalization plus two measurement channels.

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Reference graph

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