Equivalence of dynamics of disordered quantum ensembles and semi-infinite lattices

We develop a formalism for mapping the exact dynamics of an ensemble of disordered quantum systems onto the dynamics of a single particle propagating along a semi-infinite lattice, with parameters determined by the probability distribution of disorder realizations of the original heterogeneous quantum ensemble. This mapping provides a geometric interpretation on the loss of coherence when averaging over the ensemble and allows computation of the exact dynamics of the entire disordered ensemble in a single simulation. Alternatively, by exploiting the reverse map, one can obtain lattice dynamics by averaging over realisations of disorder. The potential of this equivalence is showcased with examples of the map in both directions: obtaining dephasing of a qubit via mapping to a lattice model, and solving a simple lattice model via taking an average over realizations of disorder of a unit cell.

💡 Research Summary

The authors introduce a rigorous mapping that translates the exact ensemble‑averaged dynamics of a disordered quantum system into the unitary evolution of a single particle on a semi‑infinite lattice. An ensemble is defined as a collection of non‑interacting quantum systems, each characterized by a Hamiltonian  Ĥλ = Ĥ0 + ĤV(λ) where λ = (λ1,…,λℓ) denotes a set of independent random variables drawn from a factorized probability density p(λ)=∏i p_i(λi). The goal is to compute the average density matrix
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