Fibre wavelength quantum light sources

The Cambridge team will develop quantum dot single photon emitters for Quantum Communications. The overall project
aims are to demonstrate the controlled emission of entangled photons from an LED structure emitting at a wavelength of
1.55microns. This wavelength is the standard wavelength for fibre communications. Devices operating at this wavelength
will be required to achieve commercially significant Quantum Communications technologies. However entangled photons
from quantum dots at this wavelength have not been demonstrated and there is a significant epitaxy challenge in
developing this technology.
The Cambridge team will develop Indium Arsenide quantum dots grown on Indium Phosphide substrates by Molecular
Beam Epitaxy (MBE), complementing and contrasting with the development by Metal Organic Vapour Phase Epitaxy
(MOVPE) in Sheffield. To demonstrate single photon emitters at this wavelength is challenging and there is a need to
investigate the properties of the quantum dots by both techniques to understand how the quantum dots form and what
controls the fundamental properties that will generate photon entanglement; including aspects such as the exciton spin
splitting value. The work will build significantly on the prior work carried out at shorter wavelengths in Sheffield, Toshiba
and Cavendish laboratories using a different material system. In particular at Sheffield the result of quantum dot structures
developed under an EPSRC Programme Grant will benefit the project strongly since many of the physical properties may
be similar. The demonstration of high quality devices at this wavelength will be a significant milestone in matching Quantum
Communications to the current non-quantum fibre-communications infrastructure.

Exploitable outcomes will include IPR and technology related to single photon generation, growth of quantum dots and
fabrication of quantum devices. There is also the potential for IPR on the application of the device to areas such as
quantum key distribution, quantum relays/repeaters, quantum sensors, quantum imaging and photonic quantum computing.
We will seek to exploit the outcomes of the project through a close interaction with the EPSRC Quantum Technology Hubs, especially those which have a strong focus upon photonic technologies and to which we can make a strong collaborative
contribution. It should be noted that none of the EPSRC Hubs are funded to develop quantum light sources. In
collaboration with the Quantum Communication Hub (co-ordinated by York) we will develop systems for quantum
relays/repeaters and quantum digital signatures based upon fibre wavelength entangled LEDs developed in this project.
We will explore exploitation in schemes for eye-safe quantum enhanced LIDAR in the Quantum Imaging Hub (Glasgow).
Dissemination will be achieved through patent publications, scientific papers (eg recent reports by the applicants on
quantum light generation have been published in Nature, Nature Photonics, Nature Communications and Applied Physics
Letters) and presentations at relevant international conferences (such as Photonics West, ECOC, OFC, CLEO, CLEO
Europe, QCrypt, QCMC).
The know-how developed in the project will be added to the capabilities of the National Centre for III-V Technologies and
will be available as a resource for the broader UK academic community through EPSRC, TSB or EU research grants. This
significantly increases the leverage of the project through dissemination into a broader set of R&D projects and other
applications areas such as telecommunication lasers and detectors.