Highly-efficient extraction of entangled photons from quantum dots using a broadband optical antenna

Abstract

Many quantum photonic technologies require the efficient generation of entangled pairs of photons, but to date there have been few ways to produce them reliably. Sources based on parametric down conversion operate at very low efficiency per pulse due to the probabilistic generation process. Semiconductor quantum dots can emit single pairs of entangled photons deterministically but they fall short due to the extremely low-extraction efficiency. Strategies for extracting single photons from quantum dots, such as embedding them in narrowband optical cavities, are difficult to translate to entangled photons. Here, we build a broadband optical antenna with an extraction efficiency of 65% ± 4% and demonstrate a highly-efficient entangled-photon source by collecting strongly entangled photons (fidelity of 0.9) at a pair efficiency of 0.372 ± 0.002 per pulse. The high brightness achieved by our source represents a step forward in the development of optical quantum technologies.

Entanglement Swapping with Semiconductor-Generated Photons Violates Bell’s Inequality

“…The experimental concept is sketched in Fig. 1b The QDs are embedded in a nanomembrane which is sandwiched by a silver reflector and a spacing layer, attached to a gallium phosphide hemsipherical lens [24]. This design provides a broadband optical antenna, offering photon extraction efficiencies up to 65 % while preserving a high single photon purity and entanglement fidelity.…”

“…Improvements of the past three years have overcome these limitations. Highly coherent [21] and strongly entangled photons [22,23] can now be generated with high brightness [24] and reproducibility [22] from QDs. Here we demonstrate, for the first time, entanglement swapping between polarization-entangled photons emitted by a semiconductor QD.…”

Distinctive characteristics of carrier-phonon interactions in optically driven semiconductor quantum dots

“…While QDs are interesting objects for studying the fundamentals of the carrier-phonon interaction on the nano-scale, they are likewise highly attractive candidates for applications in quantum information technology. In particular, QDs could be used as single [48][49][50][51][52][53][54][55] or pair photon sources [54,[56][57][58][59][60][61][62][63] or in quantum networks [64]. Therefore it is also of high interest to understand the impact of the carrier-phonon interaction on the properties of the photons emitted from a QD.…”

Generation of Non‐Classical Light Using Semiconductor Quantum Dots

“…Moreover, for polarization entangled photon pairs, the modes need to be bimodal to support both polarizations which is easier to achieve for low‐Q resonators. Remarkably, extraction efficiencies of 0.65 ± 0.04 was recently reported for dielectric antennas …”