# Composite two-particle sources

## TL;DR

This paper introduces a new two-particle source design using series-connected single-electron or hole emitters that can produce exactly two particles with high control, reducing decoherence effects and enabling precise quantum state manipulation.

## Contribution

The paper proposes a novel two-particle source architecture with series-connected emitters, demonstrating adiabatic and non-adiabatic regimes for controlled two-electron emission and particle annihilation.

## Key findings

- Exact two-electron emission with adiabatic driving
- Controlled electron-hole annihilation via wave function overlap
- Shot noise measurements can determine particle overlap

## Abstract

Multi-particle sources constitute an interesting new paradigm following the recent development of on-demand single-electron sources. Versatile devices can be designed using several single-electron sources, possibly of different types, coupled to the same quantum circuit. However, if combined \textit{non-locally} to avoid cross-talk, the resulting architecture becomes very sensitive to electronic decoherence. To circumvent this problem, we here analyse two-particle sources that operate with several single-electron (or hole) emitters attached in series to the same electronic waveguide. We demonstrate how such a device can emit exactly two electrons without exciting unwanted electron-hole pairs if the driving is adiabatic. Going beyond the adiabatic regime, perfect two-electron emission can be achieved by driving two quantum dot levels across the Fermi level of the external reservoir. If a single-electron source is combined with a source of holes, the emitted particles can annihilate each other in a process which is governed by the overlap of their wave functions. Importantly, the degree of annihilation can be controlled by tuning the emission times, and the overlap can be determined by measuring the shot noise after a beam splitter. In contrast to a Hong-Ou-Mandel experiment, the wave functions overlap close to the emitters and not after propagating to the beam splitter, making the shot noise reduction less susceptible to electronic decoherence.