Flying qubits Surfing on Plasmons

TL;DR

This paper develops a unified dynamical quantum transport theory that describes how single-electron wave packets in graphene propagate coherently while interacting with collective plasmonic modes, enabling better understanding of flying qubits at high frequencies.

Contribution

It introduces a gauge-invariant, self-consistent framework that combines fermionic and bosonic descriptions of quantum transport in low-dimensional conductors.

Findings

Electrons 'surf' on self-induced plasmon waves at the Fermi velocity.

The theory captures photon-assisted transport and charge relaxation.

It remains valid beyond low-frequency regimes.

Abstract

The rapid emergence of flying qubits in graphene and other low-dimensional conductors is pushing quantum electronics into an ultrafast regime where conventional transport theories no longer apply. In these systems, single-electron wave packets propagate coherently over micrometer scales while interacting with collective charge excitations on comparable time scales. Yet existing theoretical frameworks describe either fermionic single-particle dynamics or bosonic plasmonic modes, without reconciling the two. Here we introduce a unified theory of dynamical quantum transport that bridges this long-standing divide. Starting from a gauge-invariant scattering approach, we show how a time-dependent single-electron excitation self-consistently generates a propagating internal potential that behaves as a collective plasmonic mode. Electrons propagate at the Fermi velocity while simultaneously 'surfing' on this self-induced plasmon wave, whose velocity is renormalized by Coulomb interactions and screening. This dynamical mean-field framework captures photon-assisted transport, charge relaxation, and edge magnetoplasmon dynamics within a single description and remains valid far beyond the low-frequency limit. By unifying single-electron and plasmonic pictures, our results provide a timely foundation for the interpretation and control of flying-qubit experiments in graphene at gigahertz/terahertz frequencies.