Summary
Individual atoms can act as stationary qubits and thus serve as nodes in quantum computing networks or as memories for quantum repeaters. However, to successfully use qubits based on single atoms suspended in free space, photons emitted by a single atom need to be efficiently collected. Conventionally, this can be done with high numerical aperture lenses, which can collect light from a large solid angle. Alternatively, placing the atom into a high-finesse cavity or within a sub-wavelength distance from the surface of a nano-photonic structure can affect the spatial pattern in which the atom emits photons and make the photon collection more efficient. However, these approaches remain experimentally challenging and can limit the potential for realistic scalability.
This project aims to achieve a distinctly novel way to control the emission pattern of a single atom by placing the atom at a distance of a few wavelengths from a chiral metasurface — a phased two-dimensional array of nano-scale metallic antennas or dielectric scatterers. We design and fabricate bi- and multi-layer structures with properly tuned interference between the radiation patterns of the layers. In the vicinity of such structures, the atom will emit light into a single, well defined direction without the need to place the atom at a sub-wavelength distance from a metallic or dielectric surface. The unidirectionally emitted photons can be efficiently coupled into optical fibers. Relative to current state-of-the-art, this platform simplifies and enables speed-up for certain quantum information processing tasks, such as remote entanglement between two distant atoms.
Simultaneously we will explore – through design and fabrication – the use of chiral metasurfaces for photon extraction from solid-state quantum emitters, such as colour centers in diamond. Here we hope to achieve increased photon collection efficiency from materials with high refractive index, which holds promise for improving the performance (speed and sensitivity) of electric and magnetic field sensors.

Figure 1. The spatial emission pattern of an atom suspended above the tip of an optical fibre is controlled by the two-layer metasurface mounted on the fiber tip. This allows efficient collection of the photons emitted by the atom and their coupling into the fibre.
Related Content

Quantum Information Processing with Molecular Lattices
The aim of the work is to develop theoretical tools to simulate and predict the behaviour of a one-dimensional chain of trapped dipolar molecules and to study the nature of entanglement as a design resource.
June 1, 2017
Using Interactive Digital Storytelling to Represent Transformative Quantum Technologies in Augmented/Extended Reality Environments
Summary A major roadblock to the broader adoption of quantum technologies is the long learning curve associated with their seemingly abstract concepts. This often renders quantum technologies inaccessible to most audiences, especially through explanations using conventional scientific language. In this project, we develop novel methods of interactive digital storytelling – augmented and extended reality (AR/XR) […]
February 24, 2021

Ultrafast Dynamical Studies of Valley-Based Qubits
Summary As monolayers, transition metal dichalcogenides (TMDCs) – such as tungsten diselenide (WSe2) – become direct-bandgap semiconductors capable of emitting light. Compared to conventional direct-bandgap semiconductors, such as III-V semiconductors like GaAs, excitons (quasiparticles made of an electron hole bound with an electron) and single-layer TMDCs (SL-TMDCs) have much stronger binding energy. Excitons and […]
June 29, 2018

Free-space Polarization-selective Microcavity based on Chiral Metasurfaces
Summary Developing a new type of Fabry-Pérot cavity that allows improved control of the atoms’ emission into the cavity mode will result in enhancement of the efficiency and fidelity of quantum state transfer from photons to atoms and back. This in turn can be used to improve the performance of quantum networks and repeaters, as […]
September 19, 2019