Journal Article

Quantum interference between two single photons emitted by independently trapped atoms

Browaeys, A., Messin, G., Darquié, B., Beugnon, J., Grangier, P., Dingjan, J., Jones, M. P. A.

2006

Overview

Travelling light The quantum description of light as photons leads to predictions that have no classical counterpart. Coalescence is a striking example: when two identical photons arrive simultaneously at the two sides of a partially reflecting mirror, they always leave the mirror together. Beugnon et al . demonstrate this effect by producing quantum interference between two single photons emitted by two independently trapped atoms. This is a step towards synchronized, independent sources emitting indistinguishable photons. Such sources would be a useful resource for quantum data processing. A collection of synchronized, independent sources emitting indistinguishable photons represents a highly useful resource for quantum data processing. Demonstration of quantum interference between two single photons emitted by two independently trapped single atoms is an important step towards this goal. When two indistinguishable single photons are fed into the two input ports of a beam splitter, the photons will coalesce and leave together from the same output port. This is a quantum interference effect, which occurs because two possible paths—in which the photons leave by different output ports—interfere destructively. This effect was first observed in parametric downconversion 1 (in which a nonlinear crystal splits a single photon into two photons of lower energy), then from two separate downconversion crystals 2 , as well as with single photons produced one after the other by the same quantum emitter 3 , 4 , 5 , 6 . With the recent developments in quantum information research, much attention has been devoted to this interference effect as a resource for quantum data processing using linear optics techniques 2 , 7 , 8 , 9 , 10 , 11 . To ensure the scalability of schemes based on these ideas, it is crucial that indistinguishable photons are emitted by a collection of synchronized, but otherwise independent sources. Here we demonstrate the quantum interference of two single photons emitted by two independently trapped single atoms, bridging the gap towards the simultaneous emission of many indistinguishable single photons by different emitters. Our data analysis shows that the observed coalescence is mainly limited by wavefront matching of the light emitted by the two atoms, and to a lesser extent by the motion of each atom in its own trap.

• Publisher: Nature Publishing Group UK,Nature Publishing,Nature Publishing Group
• Subject: Atomic and molecular physics / Atomic properties and interactions with photons / Atoms & subatomic particles / Classical and quantum physics: mechanics and fields / Coalescence / Crystals / Data processing / Emissions / Exact sciences and technology / Humanities and Social Sciences / letter / multidisciplinary / Optical cooling of atoms; trapping / Optics / Particle physics / Photon interactions with atoms / Physics / Quantum computation / Quantum information / Quantum Physics / Quantum theory / Science / Science (multidisciplinary)