Quantum Dots Tuned for Entanglement

Researchers have applied a combination of an electric field and mechanical strain to a system of quantum dots in order to correct for asymmetries that usually prevent these semiconductor nanostructures from emitting entangled photons.

Entanglement distinguishes quantum mechanics from classical physics and as such is the core resource in most applications of quantum information science. In previous demonstrations, entangled photons have allowed fundamental tests of quantum mechanics, provided secure communication protocols, enabled computations using algorithms no classical computer could perform efficiently, and provided improvements in optical sensing and imaging [1]. Moving forward, scientists will need reliable, mass-producible sources of entangled photons. Quantum dots are a leading candidate for this role, but these “artificial atoms” suffer from structural irregularities that spoil entanglement by causing a mismatch in the energies of emitted photon pairs. New research in Physical Review Letters [2] overcomes this challenge by using two control knobs—an applied electric field and mechanical strain—that together reshape the electronic structure of the dots so that the possibility for entanglement is recovered.