Received ZZZ, revised ZZZ, accepted ZZZ Published online ZZZ (Dates will be provided by the publisher.)Keywords (quantum dot, single photon, g (2) (0), photon extraction efficiency) We introduce novel metal-embedded semiconductor pillar structure including quantum dots as highly efficient single-photon sources for quantum information applications. We have developed related processes for fabricating the proposed structure, and have demonstrated strongly suppressed multi-photon generation and improved photon extraction efficiency. As a result, under non-resonant excitation, which is highly preferable for the practical use, single-photon purity with g (2) (0) as low as 0.015 has been measured. Extremely small semiconductor volume in the metal embedded structure is a crucial factor for this observation. Moreover, single-photon generation rate from a single quantum dot up to 6.4 million per second has been achieved.Copyright line will be provided by the publisher
IntroductionFor quantum information applications, realization of efficient single-photon sources is one of the key issues. Semiconductor quantum dots (QDs) are a good candidate for realizing single-photon sources, entangled-photon-pair sources [1][2][3], and quantum gates [4] etc. Especially, in view of the single-photon sources based on QDs, high-bitrate on-demand generation is expected.However, for the practical use, two main issues are remaining. First, multi-photon generation evaluated by a second-order photon correlation function at zero time delay g (2) (0) should be minimized. For long-distance quantum key distribution, lower g (2) (0) is crucial for practical applications with high bit rate operation [5]. So far, many groups have reported single photon emission from QDs [6][7][8][9], and relatively low g (2) (0) values of 0.02-0.03 were reported in ref. 6, 7. However, these values have been obtained under p-shell resonant excitation which requires strict energy tuning. For practical devices driven by electrical pumping, further suppression of multi-photon generation without strict energy tuning is much preferable. Another issue is to approach the on-demand operation. Generally, photon extraction efficiency from QDs is less than 1% in the case of a planar surface due to large difference