Quantum interference between two single photons emitted by independently trapped atoms

Abstract

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 (in which a nonlinear crystal splits a single photon into two photons of lower energy), then from two separate downconversion crystals, as well as with single photons produced one after the other by the same quantum emitter. 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. 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.

On-demand semiconductor single-photon source with near-unity indistinguishability

“…These results demonstrate that the solid-state pulsed RF single photons in quick succession are highly indistinguishable to a level comparable to the best results from those welldeveloped systems such as parametric down-conversion [1], trapped atoms and ions [41][42][43][44]. The high-visibility results indicate a reduction of the fast dephasing and an elimination of the emission time jitter associated with the pulsed RF, compared to the previous incoherent excitation methods.…”

Sub-Rayleigh quantum imaging using single-photon sources

“…In the same way, sub-Rayleigh resolution enhanced by a factor of four is obtained for N = 4 emitters and using N = 4 detectors. By extending this scheme, we show that the same results are also obtained for different objects, e.g., in case of a grating with N slits.Only recently, first experiments were able to observe higher order interferences of photons emitted by single trapped atoms [15,16,17,18]. These observations stand in a long line of experiments using single photon sources to investigate interference phenomena of single-and multi-photon amplitudes.…”

Two-photon interferences with degenerate and nondegenerate paired photons

“…In the well-known Hong-OuMandel (HOM) interference [3,4], it was found that two identical photons coalesce in the BS and go together into the same output port. This two-photon quantum interference effect has been confirmed from paired photons in spontaneous parametric down-conversion [3], four-wave mixing [5], and single photons from independent sources [6,7]. In these experiments, the indistinguishability between the two photons is the key for observing the HOM effect where the detectors are slow as compared to the bandwidth of the photons.…”