Understanding Quantum Dissipation from an Energy Distribution Perspective:Universal Formulas for Internal Dissipation Power and the Energy Distribution Ratio f, and a Generalization of the Fluctuation-Dissipation Theorem
Based on the "Interface Projection Realism" framework, this paper rigorously derives the universal formula for internal dissipation power and the microscopic expression for the energy distribution ratio f from first principles. We treat the qubit (Q), the interfacial defect network (D), and the bulk dissipation channel (B) as a self-contained total system, no longer presupposing any part of it as an external environment. By applying the Born-Markov approximation to the degrees of freedom of D and B, we obtain the reduced master equation for Q, and subsequently calculate the net energy flow rate from Q to the incoherent degrees of freedom—the internal dissipation power R_internal. The result is: R_internal = ħω_q [Γ↓ ⟨n⟩ - Γ↑ (1-⟨n⟩)], where Γ↓ and Γ↑ are transition rates determined by the Q-D coupling and the internal structure of D, and ⟨n⟩ is the excited state population of Q. This formula does not rely on any thermal equilibrium assumptions and is applicable to arbitrary Markovian non-equilibrium steady states. Building on this, we define the total effective power absorbed by the system as R_total = ⟨∂H_drive/∂t⟩ and introduce the system's stored energy E_stored = ⟨H_Q⟩. Under periodic averaging, the energy conservation equation reads dE_stored/dt = R_total - R_internal, where the overline denotes time average. The energy distribution ratio f = R_internal / R_total satisfies f = 1 in the periodic steady state where dE_stored/dt = 0; during transients, f can deviate from 1, its specific expression depending on microscopic parameters, reflecting the degree of deviation from the steady state. We further demonstrate that when D and B are in thermal equilibrium, the above formula reduces to the traditional fluctuation-dissipation theorem. This paper proves that the universal formula for internal dissipation power naturally contains the fluctuation-dissipation theorem under thermal equilibrium conditions, while its validity in non-equilibrium states constitutes a non-equilibrium generalization of the traditional theorem, providing a unified theoretical foundation for understanding the energetic origin of quantum decoherence.
Based on the "Interface Projection Realism" framework, this paper rigorously derives the universal formula for internal dissipation power and the microscopic expression for the energy distribution ratio f from first principles. We treat the qubit (Q), the interfacial defect network (D), and the bulk dissipation channel (B) as a self-contained total system, no longer presupposing any part of it as an external environment. By applying the Born-Markov approximation to the degrees of freedom of D and B, we obtain the reduced master equation for Q, and subsequently calculate the net energy flow rate from Q to the incoherent degrees of freedom—the internal dissipation power R_internal. The result is: R_internal = ħω_q [Γ↓ ⟨n⟩ - Γ↑ (1-⟨n⟩)], where Γ↓ and Γ↑ are transition rates determined by the Q-D coupling and the internal structure of D, and ⟨n⟩ is the excited state population of Q. This formula does not rely on any thermal equilibrium assumptions and is applicable to arbitrary Markovian non-equilibrium steady states. Building on this, we define the total effective power absorbed by the system as R_total = ⟨∂H_drive/∂t⟩ and introduce the system's stored energy E_stored = ⟨H_Q⟩. Under periodic averaging, the energy conservation equation reads dE_stored/dt = R_total - R_internal, where the overline denotes time average. The energy distribution ratio f = R_internal / R_total satisfies f = 1 in the periodic steady state where dE_stored/dt = 0; during transients, f can deviate from 1, its specific expression depending on microscopic parameters, reflecting the degree of deviation from the steady state. We further demonstrate that when D and B are in thermal equilibrium, the above formula reduces to the traditional fluctuation-dissipation theorem. This paper proves that the universal formula for internal dissipation power naturally contains the fluctuation-dissipation theorem under thermal equilibrium conditions, while its validity in non-equilibrium states constitutes a non-equilibrium generalization of the traditional theorem, providing a unified theoretical foundation for understanding the energetic origin of quantum decoherence.
Important Update on March 9, 2026: In this version, the description of environmental effects has been corrected: they are now properly treated as encapsulated within the effective spectral density of the interfacial defect network D, rather than as direct driving terms. All core results and conclusions remain unchanged, but the physical interpretation is refined to align with the energy distribution framework introduced in Part II of this series. Version 2 This paper is the third in the "Interface-Projected Realism" series. This series of work aims to establish a new theoretical paradigm: Ontologically, replace probabilistic wave function descriptions with deterministic energy flow; Methodologically, redefine physical reality as an interactive whole composed of quantum units (Q), an interfacial defect network (D), and bulk channels (B). In the first work, an exact relationship between energy flow and relaxation rate was established, providing a formal bridge for the paradigm shift. In the second work, the "Energy Distribution Framework" was proposed, demonstrating that dissipation is the deterministic allocation of energy between Q and D, and deriving the universal formula for internal dissipation power Rint=ℏωq[Γ↓⟨n⟩−Γ↑(1−⟨n⟩)], where the relaxation rates are completely determined by the internal structure of D, revealing the core role of the energy distribution ratio f. This paper generalizes this new paradigm based on energy distribution from single-body to many-body systems. The core step is to define multiple Q contacts and their shared D and B together as a new, unified composite system. Within this framework, the traditionally complex "many-body correlated dissipation" is clearly interpreted as a macroscopic result of the deterministic flow of energy within this composite system, governed by allocation and transport rules determined by the structure of the D network. Through rigorous coarse-graining of this overall system, this paper derives the governing equation for the evolution of its internal energy density field u(r,t)—a classical reaction-diffusion equation:∂t∂u=Rtotal−γ0(r)u+∇⋅(γ2∇u).Here, the local dissipation rate γ0(r) and the diffusion coefficient γ2 are completely determined by the properties of the D network, corresponding respectively to the spatial distribution of the energy distribution ratio f from the second paper and the redistribution effect induced by its correlations. This theory is not only logically self-consistent but also provides a unified explanation for multiple cutting-edge experiments. This paper marks that a physical framework based on deterministic energy distribution and transport can now systematically describe many-body correlation phenomena, providing crucial support for the completeness of the new paradigm. \textbf{Keywords}: Interface-Projected Realism; Energy Distribution; Many-Body Systems; Correlated Dissipation; Reaction-Diffusion Equation Version 1 Traditional quantum theory typically attributes energy dissipation to random perturbations from the external environment. Based on the "Interfacial Projected Realism" framework, this work re-examines the nature of energy dissipation from a novel perspective, treating the qubit, the interfacial defect network, and the bulk dissipation channel as a self-contained total system. We first rigorously derive the universal formula for internal dissipation power and the energy distribution ratio f in single-body quantum systems, and then extend these concepts to many-body systems. Starting from a microscopic Hamiltonian coupling multiple qubits to a common quantized field and employing the Nakajima-Zwanzig projection operator technique, we obtain a universal expression for the energy dissipated from a many-body system to the environment. Applying this result to the specific model of multiple two-level systems coupled to a common bosonic field yields a collective master equation where the dissipation coefficient matrix Γij encodes all spatial and coupling information. Through systematic coarse-graining, gradient expansion, and semiclassical approximation, we derive for the first time from an energy-distribution perspective a closed set of macroscopic equations for the local system energy density u(r,t) and the environmental field energy density U(r,t): ∂t∂u=Rtotal(r,t)−γ0(U)u+∇⋅(γ2(U)∇u)∂t∂U=D∇2U−ΓBU+ρ(r)γ0(U)u Within this framework, the energy distribution ratio f(r,t)=γ0u/Rtotal emerges naturally as a macroscopic quantity, its physical essence being jointly determined by the system’s microscopic coupling structure (embodied by Γij) and quantum statistical state. The theory quantitatively explains several long-unexplained anomalous phenomena in cutting-edge experiments, demonstrates strong testability, and lays a solid foundation for exploring deeper connections between energy distribution and macroscopic physics. For the exact mathematical formulation and detailed derivations, please refer to the PDF file.
This paper rigorously proves the exact relation between the internal dissipation power Rinternal (the net power flowing from the system to the dissipative channel) and the energy relaxation rate Γ1 for a broad class of Markovian quantum systems. Starting from the standard Lindblad master equation incorporating an amplitude damping term, we provide a purely algebraic proof that, in the absence of driving and at zero temperature, the identity Rinternal = ℏωqΓ1⟨σ+σ−⟩ holds universally. This proof does not rely on any additional assumptions regarding the microscopic origin of Γ1 or the strength of pure dephasing. For systems subject to external driv ing, we precisely define the internal dissipation power according to the first law of quantum thermodynamics, and we provide a completely self-contained demon stration that, under the original driving form without invoking the rotating-wave approximation, the exact result is Rinternal = ℏωqΓ1⟨σ+σ−⟩ + ℏ 2 ΩΓ1 cos(ωdt)⟨σx⟩; this correction term originates from counter-rotating components and, under the rotating-wave approximation, averages to zero over time due to its fast oscilla tion, thereby recovering the same relation as in the undriven case. For finite temperature environments, we derive the modified relation Rinternal = ℏωqΓ1 [ (1+ 2nth)⟨σ+σ−⟩ − nth] and verify that it vanishes in thermal equilibrium. This arti cle elaborates on the minimal assumptions, conditions of independence, and limitations of this relation, and also presents its generalization to multi-level sys tems.
This paper achieves a fundamental reconstruction of the quantum theory paradigm based on the energy distribution framework. This framework radically steps outside the traditional description based on probability amplitude evolution, reinterpreting physical processes as deterministic energy flow among quantum units (Q), an interfacial defect network (D), and bulk dissipation channels (B). A series of previous works have laid a solid foundation for this new paradigm: the first paper rigorously proved the exact relation between internal dissipation power and energy relaxation rate, providing a mathematical link for the energy perspective; the second paper established a single-body energy distribution theory, defined the core order parameter—the energy distribution ratio f, and proved that the relaxation rate is entirely determined by the microstructure of D; the third paper extended the theory to many-body systems and, under the Markovian approximation, derived a mesoscopic diffusion equation describing energy transport within the D network. As the fourth paper in this series, this work completely abandons the Markovian approximation and constructs a universal theory of non-Markovian mesoscopic dynamics from first principles. Taking the energy density u(r,t) as the fundamental field variable, this paper derives an integro-differential equation containing memory kernels K0 and K2 by tracing over the degrees of freedom describing the defect network D and implementing spatial coarse-graining—termed herein the \textbf{generative master equation}. The essence of this equation lies in the fact that the memory kernels are completely determined by the spatial correlation function CD(+)(s,t) of the defect network D, which, as the system's "microscopic fingerprint," uniquely encodes all dynamical information of D. By selecting different forms of the correlation function, the master equation can naturally reduce to or transform into almost all known macroscopic transport equations in physics: in the Markovian limit, it returns to the diffusion equation; exponential correlation yields the telegraph equation and a finite propagation speed v=D0/τc; power-law correlation gives rise to fractional diffusion equations; nonlinear correlation leads to nonlinear diffusion equations. This unified mapping reveals the deep-seated role of the theory presented herein: it does not seek to replace existing theories but rather to provide them with a common microscopic origin. This paper also establishes a quantitative criterion for energy backflow and directly links it to the energy distribution ratio f, opening new avenues for the experimental inversion of memory kernels. This work marks the evolution of the energy distribution framework from a specific model into a generative mother theory capable of uniformly describing various transport behaviors. \textbf{Keywords}: Generative master equation; Energy distribution framework; Non-Markovian dynamics; Mesoscopic dynamics; Memory kernel; Green's function; Telegraph equation; Finite propagation speed
The fluctuation-dissipation theorem (FDT) is a cornerstone of statistical mechanics, linking the linear response of a system to external perturbations with the equilibrium fluctuations of its constituent degrees of freedom. Traditionally formulated for Hermitian quantum systems in thermal equilibrium, its applicability to non-Hermitian quantum systems, which are increasingly relevant in areas such as open quantum systems, PT-symmetric quantum mechanics, and topological phases, remains a complex and largely unresolved challenge. This paper presents a theoretical framework for a universal fluctuation-dissipation theorem applicable to a broad class of non-Hermitian quantum systems. We demonstrate how the presence of non-Hermiticity, characterized by complex energy eigenvalues and non-orthogonal eigenstates, fundamentally modifies the relationship between correlation functions and response functions. Our derivation utilizes a generalized time-evolution operator and incorporates concepts from non-Hermitian spectral theory, revealing a modified FDT that accounts for energy gain or loss inherent in these systems. The resulting theorem provides insights into the interplay between quantum noise and dissipation in environments far from conventional thermal equilibrium, offering a crucial tool for understanding and engineering non-Hermitian quantum devices. We discuss the implications for non-equilibrium steady states and the breakdown of standard notions of temperature and entropy, proposing a path towards experimental verification in platforms like photonic lattices and cold atoms with controlled losses.
Energy dissipation in a nonequilibrium steady state is studied in driven quantum Langevin systems. We study energy dissipation flow to thermal environment, and obtain a general formula for the average rate of energy dissipation using an autocorrelation function for the system variable. This leads to a general expression of the equality that connects the violation of the fluctuation-response relation to the rate of energy dissipation, the classical version of which was first studied by Harada and Sasa.
We present a general and practical theoretical framework to investigate how energy is dissipated in open quantum system dynamics. This is performed by quantifying the contributions of individual bath components to the overall dissipation of the system. The framework is based on the Nakajima-Zwanzig projection operator technique, which allows us to express the rate of energy dissipation into a specific bath degree of freedom by using traces of operator products. The approach captures system-bath interactions to all orders, but is based on second-order perturbation theory on the off-diagonal subsystem's couplings and a Markovian description of the bath. The usefulness of our theory is demonstrated by applying it to various models of open quantum systems involving harmonic oscillators or spin baths and connecting the outcomes to existing results such as our previously reported formula derived for locally coupled harmonic baths [Kim and Franco, J. Chem. Phys. 154, 084109 (2021)]. We also prove that the dissipation calculated by our theory rigorously satisfies thermodynamic principles such as energy conservation and detailed balance. Overall, the strategy can be used to develop the theory and simulation of dissipation pathways to interpret and engineer the dynamics of open quantum systems.