We theoretically derive and experimentally compare several different ways to access entropy production in a quantum process under feedback control. We focus on a bipartite quantum system realizing an autonomous Maxwell's demon scheme reported by Najera-Santos et al. [Phys. Rev. Research 2, 032025(R) (2020)], where information encoded in a demon is consumed to transfer heat from a cold qubit to a hot cavity. By measuring individual quantum trajectories of the joint demon-cavity-qubit system, we compute the entropy production with six distinct expressions derived from different approaches to the system description and its evolution. Each method uses a specific set of trajectories and data processing. Our results provide a unified view of the various meanings of irreversibility in quantum systems and pave the way for the measurement of entropy production beyond thermal frameworks.
We theoretically derive and experimentally compare several different ways to access entropy production in a quantum process under feedback control. We focus on a bipartite quantum system realizing an autonomous Maxwell's demon scheme reported by Najera-Santos et al. [Phys. Rev. Research 2, 032025(R) (2020)], where information encoded in a demon is consumed to transfer heat from a cold qubit to a hot cavity. By measuring individual quantum trajectories of the joint demon-cavity-qubit system, we compute the entropy production with six distinct expressions derived from different approaches to the system description and its evolution. Each method uses a specific set of trajectories and data processing. Our results provide a unified view of the various meanings of irreversibility in quantum systems and pave the way for the measurement of entropy production beyond thermal frameworks.
Maxwell's demon explores the role of information in physical processes. Employing information about microscopic degrees of freedom, this "intelligent observer" is capable of compensating entropy production (or extracting work), apparently challenging the second law of thermodynamics. In a modern standpoint, it is regarded as a feedback control mechanism and the limits of thermodynamics are recast incorporating information-to-energy conversion. We derive a trade-off relation between information-theoretic quantities empowering the design of an efficient Maxwell's demon in a quantum system. The demon is experimentally implemented as a spin-1/2 quantum memory that acquires information, and employs it to control the dynamics of another spin-1/2 system, through a natural interaction. Noise and imperfections in this protocol are investigated by the assessment of its effectiveness. This realization provides experimental evidence that the irreversibility in a nonequilibrium dynamics can be mitigated by assessing microscopic information and applying a feed-forward strategy at the quantum scale.
Maxwell's demon explores the role of information in physical processes.Employing information about microscopic degrees of freedom, this "intelligent observer" is capable of compensating entropy production (or extracting work), apparently challenging the second law of thermodynamics.In a modern standpoint, it is regarded as a feedback control mechanism and the limits of thermodynamics are recast incorporating information-to-energy conversion.We derive a trade-off relation between information-theoretic quantities empowering the design of an efficient Maxwell's demon in a quantum system.The demon is experimentally implemented as a spin-1=2 quantum memory that acquires information, and employs it to control the dynamics of another spin-1=2 system, through a natural interaction.Noise and imperfections in this protocol are investigated by the assessment of its effectiveness.This realization provides experimental evidence that the irreversibility in a nonequilibrium dynamics can be mitigated by assessing microscopic information and applying a feed-forward strategy at the quantum scale.
This article develops an expanded critical–propositional analysis of Patrice A. Camati and collaborators’ 2016 experimental study, “Experimental Rectification of Entropy Production by Maxwell’s Demon in a Quantum System,” published in Physical Review Letters, in systematic dialogue with the Theory of Objectivity (TO), developed by Vidamor Cabannas and Denivaldo Silva. Camati et al. implement a quantum Maxwell’s demon using nuclear magnetic resonance and a bipartite spin system in which a spin-1/2 nuclear degree of freedom functions as a microscopic memory capable of acquiring information about another spin-1/2 system and subsequently conditioning feedback operations. Their experiment provides evidence that microscopic information can be physically acquired, encoded in correlations, stored in a quantum memory, and used to mitigate nonequilibrium entropy production through feedback control. Their central information-theoretic relation expresses entropy production through information gain, quantum relative entropy, and entropy changes associated with feedback, thereby giving information a quantitatively operational role in thermodynamic dynamics (Camati et al. 2016). The present study asks whether these results establish meaningful points of contact with the modal ontology of the Theory of Objectivity, particularly its proposi- tions concerning boundaries, relational observation, composition, and the transcendent element, which TO identifies with knowledge or information produced in atomic rela- tions and, in its stronger ontological formulation, with atomic radiation. The analysis adopts a strict three-level epistemological distinction: (1) empirical confirmation of physical phenomena; (2) structural compatibility between those phenomena and TO categories; and (3) specific empirical confirmation capable of discriminating TO-derived hypotheses from explanations already available within standard quantum mechanics and information thermodynamics. The analysis finds substantial structural compatibility between the Camati experiment and TO’s relational ontology. The system–memory distinction provides an operational analogue of boundary; measurement and feedback instantiate physically realized relational observation; hierarchical quantum operations exemplify composition; and the production, storage, and causal use of microscopic information provide a particularly strong bridge to TO’s account of the transcendent informational element. Nevertheless, the experiment does not demonstrate that information constitutes a separate ontological substance, nor does it establish the TO-specific identity between information and atomic radiation. It also does not test the TO cosmogonic theorem or its cosmological eras directly. The article therefore argues that Camati et al. constitute a high-value empirical interlocutor for TO rather than a decisive confirmation of its complete ontology. A research program is proposed in which TO’s stronger information–radiation claims are converted into discriminating bridge hypotheses, including measurable covariation between information generation and radiative observables beyond standard quantum- thermodynamic expectations. On a zero-to-ten scale, the study assigns Camati et al. a dialogue score of 8.8/10 with the Theory of Objectivity. Keywords: Theory of Objectivity; Maxwell’s demon; quantum thermodynamics; information; entropy production; feedback control; quantum memory; modal ontology; atomic radiation; transcendent element; boundaries; observation; Inductive Effects; irreversibility; information thermodynamics.
This article develops an expanded critical–propositional analysis of Patrice A. Camati and collaborators’ 2016 experimental study, “Experimental Rectification of Entropy Production by Maxwell’s Demon in a Quantum System,” published in Physical Review Letters, in systematic dialogue with the Theory of Objectivity (TO), developed by Vidamor Cabannas and Denivaldo Silva. Camati et al. implement a quantum Maxwell’s demon using nuclear magnetic resonance and a bipartite spin system in which a spin-1/2 nuclear degree of freedom functions as a microscopic memory capable of acquiring information about another spin-1/2 system and subsequently conditioning feedback operations. Their experiment provides evidence that microscopic information can be physically acquired, encoded in correlations, stored in a quantum memory, and used to mitigate nonequilibrium entropy production through feedback control. Their central information-theoretic relation expresses entropy production through information gain, quantum relative entropy, and entropy changes associated with feedback, thereby giving information a quantitatively operational role in thermodynamic dynamics (Camati et al. 2016). The present study asks whether these results establish meaningful points of contact with the modal ontology of the Theory of Objectivity, particularly its proposi- tions concerning boundaries, relational observation, composition, and the transcendent element, which TO identifies with knowledge or information produced in atomic rela- tions and, in its stronger ontological formulation, with atomic radiation. The analysis adopts a strict three-level epistemological distinction: (1) empirical confirmation of physical phenomena; (2) structural compatibility between those phenomena and TO categories; and (3) specific empirical confirmation capable of discriminating TO-derived hypotheses from explanations already available within standard quantum mechanics and information thermodynamics. The analysis finds substantial structural compatibility between the Camati experiment and TO’s relational ontology. The system–memory distinction provides an operational analogue of boundary; measurement and feedback instantiate physically realized relational observation; hierarchical quantum operations exemplify composition; and the production, storage, and causal use of microscopic information provide a particularly strong bridge to TO’s account of the transcendent informational element. Nevertheless, the experiment does not demonstrate that information constitutes a separate ontological substance, nor does it establish the TO-specific identity between information and atomic radiation. It also does not test the TO cosmogonic theorem or its cosmological eras directly. The article therefore argues that Camati et al. constitute a high-value empirical interlocutor for TO rather than a decisive confirmation of its complete ontology. A research program is proposed in which TO’s stronger information–radiation claims are converted into discriminating bridge hypotheses, including measurable covariation between information generation and radiative observables beyond standard quantum- thermodynamic expectations. On a zero-to-ten scale, the study assigns Camati et al. a dialogue score of 8.8/10 with the Theory of Objectivity. Keywords: Theory of Objectivity; Maxwell’s demon; quantum thermodynamics; information; entropy production; feedback control; quantum memory; modal ontology; atomic radiation; transcendent element; boundaries; observation; Inductive Effects; irreversibility; information thermodynamics.
Entropy production is a fundamental concept in nonequilibrium thermodynamics, providing a direct measure of the irreversibility inherent in any physical process. In this work, we investigate in steady-state the enhancement of irreversibility employing coherent feedback loop. We evaluate the steady-state entropy production rate and quantum correlations by applying the quantum phase space formulation to calculate the entropy change. Our study reveals the essential contribution of coherent feedback in the thermal bath's input-noise operators, resulting in the system being driven far from thermal equilibrium. Our analysis shows that in the small-coupling limit, the entropy production rate is proportional to the quantum mutual information. We use for application the optomechanical system of Fabry-Pérot cavity, and show that the picks of the entropy production corresponding of the heating/cooling of movable mirror are improved. Therefore, we conclude that irreversibility and quantum correlations are not independent and must be analyzed jointly. The results demonstrate the possibility of enhancement of entropy production and pave the way for promising quantum thermal applications through coherent feedback loop.
We discuss the thermodynamic aspects of a single qubit based device, powered by weak quantum measurements, and feedback controlled by a quantum Maxwell's demon. We discuss both discrete and time-continuous operation of the measurement based device at finite temperature of the reservoir. In the discrete example where a demon acquires information via discrete weak measurements, we find that the thermodynamic variables including the heat exchanged, extractable work, and the entropy produced are completely determined by an information theoretic measure of the demon's perceived arrow of time. We also discuss a realistic time-continuous operation of the device where the feedback is applied after a sequence of weak measurements. In the time-continuous limit, we derive the exact finite-time statistics of work, heat and entropy changes along individual quantum trajectories of the quantum measurement process, and relate them to the demon's arrow of time.