Single photons are fundamental constituents of many quantum technologies, encoding and communicating quantum information in various degrees of freedom such as polarization, wavelength, timing, or path [1-4]. Particularly, all-optical schemes based on linear-optical quantum computing and Boson sampling problem rely principally on single photon sources with ideal properties: on-demand availability, limited frequency-bandwidth, emission into a defined spatiotemporal mode, and crucially high brightness. Optical cavities have been extensively applied to produce bright single photons sources by enhancing the interaction of optical fields with nanosized and weak emitters such as semiconductor quantum dots, organic molecules, atoms, and defects in diamond. However, controlling the position of an emitter is of utmost important, especially in plasmonic nanocavities, where optical fields are localized on the nanoscale. Moreover, ability to produce multiple identical single photon sources, which are required to form scalable quantum networks, are limited by distribution of emission wavelength due to inhomogeneous broadening of sources such as epitaxial grown QDs. During my talk, I will first present our experimental approach and fabrication process, which allows nanometer position control of an emitter in the vicinity of a plasmonic nanoantenna. Subsequently, the vectorial interaction of a molecule-nanoantenna cavity system through mapping the coupling strength with high spatial resolution will be shown, enabling a triggered, pure, ultrafast single photon source at room temperature [5,6]. Later, I will show our quantum frequency conversion scheme and result, which allow us to shift the emission wavelength of an InAs/GaAs QD source using silicon nanophotonics, and thus pave the way to applications that rely on quantum interference of single photons .  H J Kimble, “The quantum internet”, Nature 453, 1023 (2008).  T D Ladd et al., “Quantum computers”, Nature 464, 45 (2010).  T Northup and R Blatt, “Quantum information transfer using photons”, Nat. Photonics 8, 356 (2014).  B Lounis and M Orrit, “Single photon sources,” Reports Prog. Phys. 68, 1129 (2005).  A Singh et al., “Nanoscale mapping and control of antenna-coupling strength for bright single photon sources”, Nano Letters 18, 2538 (2018).  A Singh et al., “Vectorial nanoscale mapping of optical antenna fields by single molecule dipoles”, Nano Lett. 14, 4715 (2014).  A Singh et al., “Frequency conversion of a quantum dot single-photon source on a nanophotonic chip”, CLEO: Applications and Technology, USA (2018).
Anshuman Singh is a Postdoctoral Researcher in the Physical Measurement Laboratory at National Institute of Standards and Technology (NIST), Gaithersburg, USA. He received a B.TECH. in Electrical Engineering from Indian Institute of Technology (BHU) Varanasi, India and M.Sc. in Photonics from Abbe School of Photonics, Germany. He received a Ph.D. in Photonics from ICFO – The Institute of Photonic Sciences, Spain in 2016. His doctoral research focused on probing the vectorial field of plasmonic nanoantennas in order to achieve controlled nanoscale coupling of a single molecule with a resonant nanoantenna. His post-doctoral work in NIST is researching on design, fabrication, and characterization of quantum dot based integrated photonic devices and quantum frequency conversion single photon quantum dot devices.