Subtleties in the pseudomodes formalism

• URL: http://arxiv.org/abs/2509.16377v1
• Date: Fri, 19 Sep 2025 19:39:52 GMT
• Title: Subtleties in the pseudomodes formalism
• Authors: Wynter Alford, Laetitia P. Bettmann, Gabriel T. Landi,
• Abstract summary: We show that non-diagonalizability of the pseudomodes' effective single-particle non-Hermitian Hamiltonian can lead to terms in the effective spectral density.<n>We also present a method for constructing the pseudomode parameters to exactly match a fit to a spectral density.
• Score: 0.0
• License: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Abstract: The pseudomode method for open quantum systems, also known as the mesoscopic leads approach, consists in replacing a structured environment by a set of auxiliary "pseudomodes" subject to local damping that approximate the environment's spectral density. Determining what parameters and geometry to use for the auxiliary modes, however, is non-trivial and involves many subtleties. In this paper we revisit this problem of pseudomode design and investigate some of these subtleties. In particular, we examine the scenario in which pseudomodes couple to each other, resulting in an effective spectral density that is no longer a sum of Lorentzians. We show that non-diagonalizability of the pseudomodes' effective single-particle non-Hermitian Hamiltonian can lead to terms in the effective spectral density which cannot be obtained by diagonalizable non-Hermitian Hamiltonians. We also present a method for constructing the pseudomode parameters to exactly match a fit to a spectral density, and in doing so illuminate the enormous freedom in this process. The case of many uncoupled pseudomodes is explored, and we show how, contrary to conventional assumption, the effective spectral density does not necessarily converge in the limit of an infinite number of pseudomodes; we attribute this to the non-completeness of Lorentzians as basis functions. Finally, we discuss how the notion of effective spectral densities can also emerge in the context of scattering theory for non-interacting systems.

Related papers

• Regular Fourier Features for Nonstationary Gaussian Processes [0.0]
  Spectral methods treat the spectral density as a probability distribution for Monte Carlo approximation.<n>We propose regular Fourier features for harmonizable processes that avoid this limitation.<n>We demonstrate the method on locally stationary kernels and on harmonizable mixture kernels with complex-valued spectral densities.
  arXiv  Detail & Related papers  (2026-02-26T13:50:28Z)
• Exact Multi-Valley Envelope Function Theory of Valley Splitting in Si/SiGe Nanostructures [0.0]
  Valley splitting in strained Si/SiGe quantum wells is a central parameter for silicon spin qubits.<n>We formulate an exact multi-valley envelope-function model by combining Burt-Foreman-type envelope-function theory.
  arXiv  Detail & Related papers  (2026-02-16T14:36:48Z)
• Spectroscopic Search for Topological Protection in Open Quantum Hardware: The Dissipative Mixed Hodge Module Approach [0.0]
  Standard protocols model the dynamics of open quantum systems as a superposition of isolated, exponentially decaying eigenmodes.<n>We resolve this ambiguity by introducing a geometric framework based on textitDissipative Mixed Hodge Modules (DMHM)<n>We demonstrate that WFS acts as a dissipative x-ray, quantifying dissipative leakage in molecular polaritons and certifying topological isolation in Non-Hermitian Aharonov-Bohm rings.
  arXiv  Detail & Related papers  (2025-12-25T13:06:42Z)
• Grassmann Variational Monte Carlo with neural wave functions [45.935798913942904]
  We formalize the framework introduced by Pfau et al.citepfau2024accurate in terms of Grassmann geometry of the Hilbert space.<n>We validate our approach on the Heisenberg quantum spin model on the square lattice, achieving highly accurate energies and physical observables for a large number of excited states.
  arXiv  Detail & Related papers  (2025-07-14T13:53:13Z)
• Non-Hermitian topology and skin modes in the continuum via parametric processes [44.99833362998488]
  We show that Hermitian, nonlocal parametric pairing processes can induce non-Hermitian topology and skin modes.<n>Our model, stabilized by local dissipation, reveals exceptional points that spawn a tilted diabolical line in the dispersion.
  arXiv  Detail & Related papers  (2025-05-05T16:38:20Z)
• Avoided-crossings, degeneracies and Berry phases in the spectrum of quantum noise through analytic Bloch-Messiah decomposition [49.1574468325115]
  "analytic Bloch-Messiah decomposition" provides approach for characterizing dynamics of quantum optical systems.<n>We show that avoided crossings arise naturally when a single parameter is varied, leading to hypersensitivity of the singular vectors.<n>We highlight the possibility of programming the spectral response of photonic systems through the deliberate design of avoided crossings.
  arXiv  Detail & Related papers  (2025-04-29T13:14:15Z)
• Quasi-Lindblad pseudomode theory for open quantum systems [6.184495862486372]
  We introduce a new framework to study the dynamics of open quantum systems with linearly coupled Gaussian baths. Our approach replaces the continuous bath with an auxiliary discrete set of pseudomodes with dissipative dynamics. We show that this quasi-Lindblad pseudomode formulation leads to a representation of the bath correlation function in terms of a complex weighted sum of complex exponentials.
  arXiv  Detail & Related papers  (2024-08-28T04:26:13Z)
• Nodal Spectral Functions Stabilized by Non-Hermitian Topology of Quasiparticles [0.0]
  We discuss how the abundance and stability of nodal phases is drastically affected by NH topology. We study a microscopic lattice model in which a sublattice-dependent interaction stabilizes nodal spectral functions.
  arXiv  Detail & Related papers  (2024-05-08T18:00:06Z)
• Quantum electrodynamics of lossy magnetodielectric samples in vacuum: modified Langevin noise formalism [55.2480439325792]
  We analytically derive the modified Langevin noise formalism from the established canonical quantization of the electromagnetic field in macroscopic media. We prove that each of the two field parts can be expressed in term of particular bosonic operators, which in turn diagonalize the electromagnetic Hamiltonian.
  arXiv  Detail & Related papers  (2024-04-07T14:37:04Z)
• Indistinguishability of identical bosons from a quantum information theory perspective [0.0]
  We present a general theory of indistinguishability of identical bosons in experiments consisting of passive linear optics followed by particle number detection. We identify the expectation value of the projector onto the $N$-particle symmetric subspace as an operationally meaningful measure of indistinguishability. We show that these states are diagonal in the computational basis up to a permutationally invariant unitary.
  arXiv  Detail & Related papers  (2023-07-13T08:45:51Z)
• Topological multi-mode waveguide QED [49.1574468325115]
  We show how to take advantage of topologically protected propagating modes by interfacing them with quantum emitters. Such capabilities pave the way for generating quantum gates among topologically protected photons as well as generating more complex entangled states of light in topological channels.
  arXiv  Detail & Related papers  (2022-07-05T14:48:50Z)
• Exact solutions of interacting dissipative systems via weak symmetries [77.34726150561087]
  We analytically diagonalize the Liouvillian of a class Markovian dissipative systems with arbitrary strong interactions or nonlinearity. This enables an exact description of the full dynamics and dissipative spectrum. Our method is applicable to a variety of other systems, and could provide a powerful new tool for the study of complex driven-dissipative quantum systems.
  arXiv  Detail & Related papers  (2021-09-27T17:45:42Z)
• Generalized theory of pseudomodes for exact descriptions of non-Markovian quantum processes [0.0]
  We develop an exact framework to describe the non-Markovian dynamics of an open quantum system. We show how expanding the system using discrete modes allows for the full inclusion of non-Markovian effects.
  arXiv  Detail & Related papers  (2020-02-22T17:45:34Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.