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Quantum Telescoping Part VII: Telescoping for Open Quantum Systems (Lindbladian Dynamics)

Joshua Bald

Published Feb 4, 2026• 0 citations
Publisher

Abstract

This paper extends the theory of quantum telescoping to open quantum systems governedby Lindblad generators. We develop a comprehensive channel-level telescoping framework forcompletely positive trace-preserving (CPTP) semigroups and conduct a rigorous analysis ofachievable convergence rates in Lindbladian simulation. We show that dissipative dynamicswith non-normal generators admit at best power-law telescoping under physically reasonableoracle models, in sharp contrast with the exponential telescoping possible for Hamiltonian evolution.We identify structural conditions—such as normality, commutativity, or unitary dilation—under which faster convergence may occur, and we establish that the absence of efficientquantum signal processing mechanisms obstructs exponential telescoping for typical non-normalLindbladians. We provide detailed convergence analysis, explicit error bounds, computationalcomplexity characterizations, and concrete examples including a non-normal toy model illustratingpseudospectral obstructions. These results establish fundamental limits on open-systemsimulation and clarify the distinction between coherent and dissipative quantum dynamics froma telescoping perspective, with implications for quantum algorithm design, noise modeling, andquantum thermodynamics.

DOI
10.5281/zenodo.18487036

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This paper extends the theory of quantum telescoping to open quantum systems governedby Lindblad generators. We develop a comprehensive channel-level telescoping framework forcompletely positive trace-preserving (CPTP) semigroups and conduct a rigorous analysis ofachievable convergence rates in Lindbladian simulation. We show that dissipative dynamicswith non-normal generators admit at best power-law telescoping under physically reasonableoracle models, in sharp contrast with the exponential telescoping possible for Hamiltonian evolution.We identify structural conditions—such as normality, commutativity, or unitary dilation—under which faster convergence may occur, and we establish that the absence of efficientquantum signal processing mechanisms obstructs exponential telescoping for typical non-normalLindbladians. We provide detailed convergence analysis, explicit error bounds, computationalcomplexity characterizations, and concrete examples including a non-normal toy model illustratingpseudospectral obstructions. These results establish fundamental limits on open-systemsimulation and clarify the distinction between coherent and dissipative quantum dynamics froma telescoping perspective, with implications for quantum algorithm design, noise modeling, andquantum thermodynamics.
This paper develops a telescoping framework for inverse problems in quantum dynamics, focusingon parameter recovery from quantum channels. We study families of channels {Φ(θ)}θ∈Θgenerated by unknown Hamiltonian or Lindbladian parameters and analyze how telescopingrefinement controls the resolution of parameter estimation. We show that telescoping orderbounds the achievable rate of inverse convergence and establish lower bounds linking parameteridentifiability to channel distinguishability. In particular, we prove that exponential telescopingof forward simulation is necessary to achieve logarithmic resolution in inverse problems, whilepower-law telescoping implies polynomial sample and query complexity. These results providefundamental limits on parameter estimation accuracy as a function of computational resources,unifying quantum simulation, quantum metrology, and inverse problems under a single telescopingperspective. We establish concrete complexity bounds for Hamiltonian learning andLindbladian tomography, showing that the latter is intrinsically harder due to the absence ofexponential telescoping in dissipative dynamics. Numerical simulations validate the predictedscaling laws for both power-law and exponential telescoping regimes.
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This paper establishes structural lower bounds on query complexity and refinement cost forquantum telescoping schemes. Building on the channel-level telescoping framework developed inParts I and II, we show that the decay rate of telescoping increments directly constrains the minimumnumber of oracle queries required to achieve a given simulation accuracy within the class ofrefinement-structured algorithms. We prove general lower bounds relating power-law telescopingorder to polynomial query complexity, and show that exponential telescoping is necessaryto achieve logarithmic dependence on the error tolerance. These results explain, from a structuralperspective, why quantum signal processing (QSP) and related eigenvalue-transformationmethods attain near-optimal ε-dependence in standard block-encoding models [3, 7, 8], whileproduct-formula and randomized product-formula methods remain algebraically convergent inε [10, 11]. Our analysis applies to unitary channels, CPTP maps, and block-encoded oraclemodels, and provides a unifying framework relating algorithmic structure to query complexity.We clarify the relationship between our results and known information-theoretic lower bounds,positing our theorems as structural constraints on algorithmic approaches rather than fundamentaloracle lower bounds.
Understanding the structure and stability of open quantum dynamics is increasingly important for both fundamental studies of nonequilibrium quantum systems and the development of quantum simulation algorithms. In this work, we introduce a structural framework for Markovian open quantum systems that characterizes Lindbladian generators in terms of two scalar quantities: the dissipative strength and the non-normality. We show that normal generators admit an exact decoupling between dissipative and norm-preserving dynamics, leading to purely exponential behavior governed by the dissipative scale. In contrast, non-normality is an intrinsically dissipative feature: it vanishes in the absence of dissipation but is not implied by it. Moreover, it is structurally constrained by the interplay between the Hermitian and anti-Hermitian components of the generator. For generic Markovian open quantum systems, we identify parametric regimes controlled by a dimensionless ratio between non-normality and dissipative strength, governing the onset of transient amplification. These structural features have direct implications for quantum simulation. While Hamiltonian and normal dissipative dynamics exhibit stable evolution with standard scaling behavior, non-normal generators can induce transient growth that amplifies numerical errors and increases simulation cost. Our results provide a unified generator-level perspective on irreversibility, stability, and quantum simulation of open quantum systems.
This paper develops the theory of quantum telescoping for quantum channels, with a particularfocus on Hamiltonian simulation. Building on the axiomatic framework introduced in QuantumTelescoping Part I [11], we formalize channel-level telescoping schemes using the diamondnorm, analyze convergence and error propagation under composition, and establish rigorous connectionsbetween telescoping order and simulation complexity. We show that product-formulamethods exhibit power-law telescoping with polynomial increment decay, while quantum signalprocessing induces exponential telescoping with increment decay e−ad, yielding the optimalO(t+log(1/ε)) complexity. LCU implementations of truncated series achieve super-polynomial(factorial) decay. This perspective yields transparent complexity bounds, clarifies the role of incrementalrefinement in quantum simulation, and provides a unifying framework for comparingclassical and quantum simulation strategies.
These notes are a short introduction to the mathematical theory of open quantum systems. They are meant to serve as an entry point into a broad research area which has applications across the quantum sciences dealing with systems subjected to external noise. The guiding idea is to let the key structures of the theory emerge from a concrete model. By working through the dissipative Jaynes-Cummings model the reader will dis- cover explicitly how irreversible dynamics arises from a unitary system-reservoir evolution. The notions of the continuous mode limit, correlation functions, spectral density appear in a natural manner and lead to the evolution equation of the open system in form of a master equation. This sets the stage for the more general analysis of completely positive, trace preserving (CPTP) maps and the study of quantum dynamical semigroups. We motivate and prove the Kraus representation theorem, the dilation theorem and the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) theorem. Working through the exercises (for which full solutions are supplied) will reinforce the ideas introduced in the main text.