Entanglement on demand through time reordering

TL;DR

This paper proposes a novel, lossless method to generate polarization-entangled photon pairs on demand by reordering photons in time, manipulating quantum chronology without destroying entanglement.

Contribution

It introduces a new scheme using unitary time reordering to produce entangled photons from radiative decay cascades, overcoming prior limitations of which-path information.

Findings

The scheme achieves polarization entanglement after time reordering.

It demonstrates that quantum chronology can be manipulated losslessly.

The theory is applicable to semiconductor quantum dots.

Abstract

Entangled photons can be generated "on demand" in a novel scheme involving unitary time reordering of the photons emitted in a radiative decay cascade. The scheme yields polarization entangled photon pairs, even though prior to reordering the emitted photons carry significant "which path information" and their polarizations are unentangled. This shows that quantum chronology can be manipulated in a way that is lossless and deterministic (unitary). The theory can, in principle, be tested and applied to the biexciton cascade in semiconductor quantum dots.