We propose a single-particle source which emits into the helical edge states of a two-dimensional quantum spin Hall insulator. Without breaking time-reversal symmetry, this source acts like a pair of noiseless single-electron emitters which each inject separately into a chiral edge state. By locally breaking time-reversal symmetry, the source becomes a proper single-particle emitter which exhibits shot noise. Due to its intrinsic helicity, this system can be used to produce time-bin entangled pairs of electrons in a controlled manner. The shot noise created by the source is related to the concurrence of the emitted state.
@article{arxiv.1307.1225,
title = {Emission of time-bin entangled particles into helical edge states},
author = {Patrick P. Hofer and Markus Büttiker},
journal= {arXiv preprint arXiv:1307.1225},
year = {2014}
}