Nanowire-based sources of non-classical light

Abstract

Sources of quantum light that utilize photonic nanowire designs have emerged as potential candidates for high efficiency non-classical light generation in quantum information processing. In this review we cover the different platforms used to produce nanowire-based sources, highlighting the importance of waveguide design and material properties in achieving optimal performance. The limitations of the sources are identified and routes to optimization are proposed. State-of-the-art nanowire sources are compared to other solid-state quantum emitter platforms with regard to the key metrics of single photon purity, indistinguishability and entangled-pair fidelity to maximally entangled Bell states. We also discuss the unique ability of the nanowire platform to incorporate multiple emitters in the same optical mode and consider potential applications. Finally, routes to on-chip integration are discussed and the challenges facing the development of a nanowire-based scalable architecture are presented.

On‐Chip Integration of Single Photon Sources via Evanescent Coupling of Tapered Nanowires to SiN Waveguides

“…This greatly simplifies the fabrication process, eliminating the need of alignment marks, and facilitates the fabrication of the complex circuitry required in the applications listed above. Finally, the evanescent approach described here takes advantage of the well‐controlled taper grown as part of the nanowire that contains only a single quantum dot. Hence, the spatial positioning of the single emitters is deterministic in contrast with previous evanescent coupling methods which used etched tapers in layers containing an ensemble of randomly positioned emitters.…”

“…It consists of a tapered InP nanowire placed on top of a SiN ridge waveguide. A single InAsP quantum dot is located in the untapered base of the nanowire which has a diameter D b chosen to confine the fundamental mode . The upper section of the nanowire waveguide is tapered to evanescently transfer the mode to the SiN waveguide.…”

“…We use InAsP/InP nanowire quantum dot sources grown using a combined selective‐area and vapor–liquid–solid (VLS) epitaxy approach which have demonstrated single photon purities greater than 99% and near‐transform‐limited linewidths of less than 4 µeV . Importantly, the nanowires can be grown with well‐defined tapers that can be tailored for optimal evanescent coupling.…”

“…Since the quantum dot emission is equally likely to emit in the forward and backward directions along the nanowire, one can estimate the evanescent coupling efficiency from twice the source efficiency (i.e., 56%). If we account for 5% emission into leaky modes (i.e., β = 95%) and 20% emission into phonon sidebands at 4 K (not included in the measured counts obtained using a lorentzian fit) the evanescent coupling efficiency is 74%. We note that this is an upper bound as we expect a small contribution () from photons emitted toward the base of the nanowire that are back‐reflected toward the taper.…”

“…A single InAsP quantum dot is located in the untapered base of the nanowire which has a diameter D b chosen to confine the fundamental HE 11 mode. [27,28] The upper section of the nanowire waveguide is tapered to evanescently transfer the HE 11 mode to the SiN waveguide. We assume that the quantum dot is polarized to optimally couple to the TE mode of the nanowirewaveguide system.…”