Quantum Interference with Single Molecules: Steps Towards a Competitive Single-Photon Source

Single molecules of polyaromatic hydrocarbons (PAH) in suitable host matrices are known for emitting with high quantum efficiency in very narrow and stable zero-phonon lines (ZPL) [1]. For our experiments we used dibenzotherrylene (DBT) molecule inserted as impurity in anthracene (Ac) nanocrystals, dispersed on a gold substrate and cooled down to 3 K in a closed-cycle cryostat. DBT in Ac features a single-photon dipole-allowed transition around 784 nm. Each molecule is namely identical but environmental conditions like local trapped charges or crystal strain can shift the frequency of its transition in a range of approximately 1 nm [2]. Those static differences alongside any instantaneous interaction with the environment can degrade the ability of the emitted photons to undergo two-photon interference (TPI).