Coherent generation of non-classical light on a chip via photon-induced tunnelling and blockade

Analysis of the optical characteristics of a chip-based photonic crystal cavity embedded with a quantum dot demonstrates the occurrence of both photon tunnelling and photon blockade phenomena. Such behaviour could prove useful in the development of single-photon transistors and detectors. Quantum dots in photonic crystals are interesting because of their potential in quantum information processing 1 , 2 and as a testbed for cavity quantum electrodynamics. Recent advances in controlling 3 , 4 and coherent probing 5 , 6 of such systems open the possibility of realizing quantum networks originally proposed for atomic systems 7 , 8 , 9 . Here, we demonstrate that non-classical states of light can be coherently generated using a quantum dot strongly coupled to a photonic crystal resonator 10 , 11 . We show that the capture of a single photon into the cavity affects the probability that a second photon is admitted. This probability drops when the probe is positioned at one of the two energy eigenstates corresponding to the vacuum Rabi splitting, a phenomenon known as photon blockade, the signature of which is photon antibunching 12 , 13 . In addition, we show that when the probe is positioned between the two eigenstates, the probability of admitting subsequent photons increases, resulting in photon bunching. We call this process photon-induced tunnelling. This system represents an ultimate limit for solid-state nonlinear optics at the single-photon level. Along with demonstrating the generation of non-classical photon states, we propose an implementation of a single-photon transistor 14 in this system.