arXiv subjects

Alberto Acevedo

Publications and source records attributed to Alberto Acevedo.

7 recordsLinked to original sources

arXiv2026

Arnold--Nielsen Geometry for Complexity-Deformed Noncommutative Transport

We deform the Carlen--Maas--Wirth framework for noncommutative dynamical optimal transport by an Arnold--Nielsen type complexity operator. A positive state-independent operator $G$ compatible with the Hilbert bimodule structure of a noncommutative differential calculus $\partial\colon\M\to\Hcal$ can be absorbed into the calculus itself, \[ \partial_G:=G^{1/2}\partial. \] The corresponding complexity-weighted transport problem is exactly the unweighted transport problem generated by $\partial_G$, whenever the deformed quadratic form remains Dirichlet. In finite dimensions we prove existence of minimizers for density-dependent Petz-class metrics and for fixed physical complexity weights, the latter without commutation between $G$ and the state-dependent mobility. On unitary orbits we identify the induced distance with a quotient metric coming from a right-invariant complexity geometry. This yields an exact Bell-state preparation result via Clairaut's relation and an exactly computed restricted-path upper bound for GHZ preparation; the Lindblad detailed-balance case is included only as entropy-gradient-flow background.

quant-ph↗

arXiv2026

Geometric Complexity of Quantum Channels via Unitary Dilations

Nielsen's geometric approach to quantum circuit complexity provides a Riemannian framework for quantifying the cost of implementing unitary (closed--system) dynamics. For open dynamics, however, the reduced evolution is described by quantum channels and admits many inequivalent Stinespring realizations, so any meaningful complexity notion must specify which microscopic resources are counted as accessible and which transformations are regarded as gauge. We introduce and analyze a geometric complexity functional for families of quantum channels based on unitary dilations. We distinguish an implementation-dependent complexity, defined relative to explicit dilation data, from an intrinsic channel complexity obtained by minimizing over a physically motivated class of admissible dilations (e.g. bounded environment dimension, energy or norm constraints, and penalty structures). The functional has a subtractive form: it compares the geometric cost of the total unitary realization with a canonical surrogate term that removes purely environmental contributions. We justify this subtraction from concise postulates, including closed-system consistency, environment-only neutrality, and invariance under dilation gauge transformations that leave the channel unchanged. This leads to a companion quantity, noise complexity, quantifying the loss of geometric complexity relative to a prescribed ideal closed evolution. We establish a coherence-based lower bound for unitary geometric complexity, derive structural properties such as linear time scaling under time-homogeneous dilations, and obtain dissipator--controlled bounds in the Markovian (GKSL/Lindblad) regime under a standard dilation construction. Finally, we illustrate the framework on canonical benchmark noise models, including dephasing, amplitude damping, and depolarizing (Pauli) channels.

quant-ph↗

arXiv2025

Geometric Measures of Complexity for Open and Closed Quantum Systems

The unitary dynamics of quantum systems can be modeled as a trajectory on a Riemannian manifold. This theoretical framework naturally yields a purely geometric interpretation of computational complexity for quantum algorithms, a notion originally developed by Michael Nielsen (Circa, 2007). However, for nonunitary dynamics, it is unclear how one can recover a completely geometric characterization of Nielsen-like geometric complexity. The main obstacle to overcome is that nonunitary dynamics cannot be characterized by Lie groups (which are Riemannian manifolds), as is the case for unitary dynamics. Building on Nielsen's work, we present a definition of geometric complexity for a fairly generic family of quantum channels. These channels are useful for modeling noise in quantum circuits, among other things, and analyze the geometric complexity of these quantum channels.

quant-ph↗

arXiv2024

Finite-time quantum equilibration for continuous variables

Leveraging the techniques found in the literature on Quantum Equilibration for finite dimensional systems, we develop the theory of Quantum Equilibration for the case of infinite-dimensional systems, particularly the cases where the dynamics-generating Hamiltonians have continuous spectrum. The main goal of this paper will be to propose a framework to extend the results obtained by Short in, where estimates for the equilibration-on-average and effective equilibration for the case of Hamiltonians with continuous spectrum are derived. We will show that in the latter setting, it is compulsory to constrain ourselves to finite time equilibration; we then develop estimates analogous to the main results in the proposed setting.

quant-ph↗

arXiv2024

Spectrum Broadcast Structures from von Neumann type interaction Hamiltonians with continuous variables

In this paper, we contribute to the mathematical foundations of the recently established theory of Spectrum Broadcast Structures (SBS). These are multipartite quantum states, encoding an operational notion of objectivity and exhibiting a more advanced form of decoherence. We study SBS and asymptotic convergence to SBS in the case of a central system interacting with N environments via the von Neumann-type measurement interactions, ubiquitous in the theory of open quantum systems. We will be focusing on the case where the system is modeled by an infinite-dimensional Hilbert space and the operators associated with the system in the Hamiltonian have purely continuous spectrum. Such a setup yields mathematical complications that have hitherto not been addressed in the theory of SBS.

quant-ph↗

arXiv2024

Spectrum Broadcast Structures from von Neumann type interaction Hamiltonians

In this paper, we contribute to the mathematical foundations of the recently established theory of Spectrum Broadcast Structures (SBS). These are multipartite quantum states, encoding an operational notion of objectivity and exhibiting a more advanced form of decoherence. We study SBS in the case of a central system interacting with N environments via the von Neumann-type measurement interactions, ubiquitous in the theory of open quantum systems. We state and prove a novel sufficient condition for SBS to arise dynamically for finite-dimensional systems. The condition is based on the Gram-Schmidt orthogonalization rather than on the Knill-Barnum error estimation used before.

quant-ph↗

arXiv2024

Asymptotic Quantum State Discrimination for Mixtures of Unitarily Related States

Given a mixture of states, finding a way to optimally discriminate its elements is a prominent problem in quantum communication theory. In this paper, we will address mixtures of density operators that are unitarily equivalent via elements of a one-parameter unitary group, and the corresponding quantum state discrimination (QSD) problems. We will be particularly interested in QSD as time goes to infinity. We first present an approach to QSD in the case of countable mixtures and address the respective asymptotic QSD optimization problems, proving necessary and sufficient conditions for minimal error to be obtained in the asymptotic regime (we say that in such a case QSD is fully solvable). We then outline an analogous approach to uncountable mixtures, presenting some conjectures that mirror the results presented for the cases of countable mixtures. As a technical tool, we prove and use an infinite dimensional version of the well-known Barnum-Knill bound.

math-ph↗