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arXiv:2609.22826

The Filtering Demon: Beyond Standard Thermodynamic Bounds and Harnessing Measurement Error and Quantum Friction

Yang Xiao, Jin Wang

quant-phSubmitted Sep 19, 2026• Announced Sep 22, 2026
arXivHTMLPDF

Abstract

Standard stochastic heat engines operate blindly, enforcing work extraction protocols indiscriminately on microstates, and consequently suppressing work output, stability, efficiency. To overcome this, we propose an Otto information engine (OIE) that employs a Maxwell's demon to filter out detrimental stochastic trajectories, and demonstrate that the OIE can provide enhanced work output and stability compared to the corresponding standard Otto engine. Remarkably, even after accounting for the energetic costs of the demon, the OIE efficiency surpasses both the standard Otto limit and Carnot bound. Furthermore, by applying the fluctuation theorem of information dissipation, we derive upper and lower bounds on efficiency, confirming that our results adhere to the second law of thermodynamics. Finally, and counterintuitively, measurement errors and quantum inner friction, traditionally considered deleterious, can be harnessed as resources, which improves robustness and enables us to ignore the adiabatic strokes time.

Comments
15 pages, 9 figures

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•Oct 18, 2026•0 citations
Standard stochastic heat engines operate blindly, enforcing work extraction protocols indiscriminately on microstates, and consequently suppressing work output, stability, efficiency. To overcome this, we propose an Otto information engine (OIE) that employs a Maxwell's demon to filter out detrimental stochastic trajectories, and demonstrate that the OIE can provide enhanced work output and stability compared to the corresponding standard Otto engine. Remarkably, even after accounting for the energetic costs of the demon, the OIE efficiency surpasses both the standard Otto limit and Carnot bound. Furthermore, by applying the fluctuation theorem of information dissipation, we derive upper and lower bounds on efficiency, confirming that our results adhere to the second law of thermodynamics. Finally, and counterintuitively, measurement errors and quantum inner friction, traditionally considered deleterious, can be harnessed as resources, which improves robustness and enables us to ignore the adiabatic strokes time.
Generally, the work output of stochastic heat engines is governed by the stochastic trajectory distribution and the energy spectrum. Because the trajectory distribution depends on the thermal reservoir temperatures, the work output is not only constrained by temperature but is also susceptible to thermal fluctuations. To address these limitations, we introduce two continuous Maxwell's demons into a quantum Otto cycle, forming an Otto information engine (OIE). We demonstrate that the work output of the OIE depends solely on the energy level gap, enabling arbitrary work extraction while eliminating work fluctuations, thereby ensuring cycle-to-cycle identical work output. Furthermore, we show that the engine's efficiency can surpass the standard Carnot efficiency even after accounting for the energy cost of demon's memory erasure. Finally, we show that the OIE can deliver superior output power even when the demon's measurement time is taken into account, and the corresponding Monte Carlo simulation has been executed.
Generally, quantum heat engines driven by Gibbs reservoirs achieve their maximum work and efficiency only in quasi-static processes, a constraint that hampers practical applications due to the resulting vanishing power output. To address this fundamental limitation, we propose a finite-time quantum Otto information engine (OIE) driven by a Maxwell's demon paired with a single Gibbs reservoir. We demonstrate that the demon's measurement and feedback control can preserve quantum coherence to extract coherent work, while harnessing quantum internal friction as a work source. Consequently, the OIE can produce work by only modulating the eigenstates of the Hamiltonian, and surpass the quasi-static limits of its conventional counterpart in the work output and the efficiency, which accounts for the energetic cost of the demon. Notably, the OIE can achieve near-perfect efficiency alongside positive work extraction in the rapid-driving regime.
The second law of thermodynamics holds that the efficiency of heat engines, classical or quantum, cannot be greater than the universal Carnot efficiency. We discover another bound for the efficiency of a quantum Otto heat engine consisting of a harmonic oscillator. Dynamics of the engine is governed by the Lindblad equation for the density matrix, which is mapped to the Fokker-Planck equation for the quasiprobability distribution. Applying stochastic thermodynamics to the Fokker-Planck equation system, we obtain the ℏ-dependent quantum mechanical bound for the efficiency. It turns out that the bound is tighter than the Carnot efficiency. The engine achieves the bound in the low-temperature limit where quantum effects dominate. Our work demonstrates that quantum nature could suppress the performance of heat engines in terms of efficiency bound, work, and power output.
Abstract We propose a quantum Otto engine operating through a cycle of two isochoric processes, where the working substance interacts with a single-mode radiation field, and two unitary strokes, during which the working substance is decoupled from the field. We investigate the influence of quantum superposition and quantum internal friction on the engine’s power output and efficiency, demonstrating that these quantum effects enhance both performance metrics. While these enhancements are accompanied by increased power fluctuations, we show that such fluctuations can be effectively mitigated through careful selection of control parameters. Our results reveal that the proposed quantum Otto engine can achieve performance regimes that are thermally inconceivable in classical systems, including surpassing the Otto efficiency limit and attaining 100% efficiency with nonzero power output.
Subsystems of a composite system in a pure state generally exist in mixed states and undergo changes with the overall state. This phenomenon arises from the coherence of the entire system and represents a crucial distinction between quantum and classical systems. Such a quantum property can enhance the work output of an Otto heat engine composed of two qubits, whose parameters evolve in opposite directions. When the energy levels of the two qubits are identical at one of the thermal equilibrium states of the Otto cycle and there is no interaction between them, the total work output is strictly negative, which is guaranteed by the second law of thermodynamics. However, the interaction-induced coherence allows for positive work output under such conditions. Our model provides an autonomous implementation of Maxwell’s demon, where the measurement and feedback operations are driven by an adiabatically evolved Hamiltonian without external intervention. Furthermore, the coherence of the entire system is amplified by the heat reservoir after measurement, which is the key of the positive work output. Conversely, the quantum measurement-erase cycle typically outputs negative work, attributed to the decoherence of the instrument during the measurement process.
We present a unified theoretical, numerical, and experimental investigation into autonomous information heatengines (Maxwell’s demons), bridging microscopic open quantum thermodynamics, stochastic continuous moni-toring, deep reinforcement learning, and practical energy harvesting engineering. First, addressing widespreadnumerical pitfalls in quantum thermodynamics simulations, we identify an operator sign inversion in detailed-balance jump rates that previously simulated an unphysical “perpetual motion machine” yielding −19.29 kB T .Once corrected via adaptive Runge-Kutta integration, we prove that single-step work extraction from maximallyentangled Bell states is strictly bounded by kB T ln 2, and that the cyclic entropy accounting of entanglement re-generation imposes a net non-negative work cost (Wnet ≥ 0), establishing quantum entanglement as a consumedthermodynamic fuel rather than a violation of the Second Law. Second, using positive-preserving Rouchon-Ralphstochastic master equation mappings across 48 trajectory ensembles, we evaluate an Information Conveyor Beltin a 10-dot chain under continuous homodyne detection. We demonstrate that while an isolated cryogenic demonreservoir (TM = 4.2 K) enables positive extracted power, incorporating the mandatory Carnot refrigeration over-head required to maintain the cryostat exactly cancels all efficiency advantages, yielding an overall system deficitmatching the isothermal baseline. Third, we address autonomous control in partially observable Markov deci-sion processes (POMDPs) by deploying Recurrent Proximal Policy Optimization (Recurrent PPO with LSTM),enabling the demon to autonomously overcome measurement backaction and discover synchronized conveyor trans-port policies superior to classical heuristics. Finally, we design and verify Configuration D, a body-heat-poweredthermoelectric energy harvester operating an ESP32-C3 microcontroller demon. By eliminating idle wake-timedelays and overlapping 9-bit digital sensor conversion with sub-millisecond USB polling, firmware v2 slashes ac-tive controller consumption in our calibrated design model by a factor of 8.7 (from ≈ 208.5 mJ to ≈ 24.1 mJ),establishing a net-positive self-powered operational cycle (+65.8 mJ/cycle). We quantify the fundamental gap of≈ 8.4 × 1018 (≈ 19 orders of magnitude) between the Landauer erasure limit (2.87 × 10−21 J) and real-worldmicrocontrollers, delineating the rigorous boundary between physical information thermodynamics and real-worldenergy harvesting.