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QuiLT Project Set to Increase Quantum Emission Capability

Tue, 21 March, 2023

Partners Micron Semiconductor Ltd (MSL), Powerlase Limited (PPL), and the Essex Innovation Centre ( – a partnership between the University of Essex and TWI) – have been successful in securing funding from Innovate UK, through the ISCF Commercialising quantum technologies challenge: feasibility studies, round 3, competition which aims to advance the commercialisation of quantum technologies in the UK – for the QuilLT project which will conceive a much-needed new technology for the quantum computing industry.

In the ongoing race for quantum processor development, photonic entanglement shows great promise in being able to simplify the complexity of systems and significantly reduce the cost per device. Entanglement is considered one of the most important features of quantum information science. Meanwhile, a number of companies are currently involved in photonic quantum processors, but much further development is required for commercialisation.

A Quantum Key Distributor (QKD) is a simple device that utilises quantum entanglement to encode information. Quantum key distribution with entangled photons requires high brightness sources of entangled photons, and can be attained within either space or time domain constraints placed on the emission process. Semiconductor sources that can emit quantum entangled photons within short time constraints show greater potential for use than spontaneous, parametric down-conversion SPDC sources, provided that issues prohibiting their ease of on-chip integration can be overcome.

To achieve on-chip integration, quantum distributors (QDs) need to be either grown by self-assembly, on determined sites of a photonic integrated circuit (PIC) or on a PIC part of an electronic chip. However, small misalignments in the relative positioning of the QD with respect to the circuit can lead to severe reductions in device efficiency. Misalignment in self-assembled QDs can be controlled by constructing and placing the circuit around the position of the QD, but this is not scalable because the PIC layout has to be modified each time to follow the distribution of the QDs.

The use of predetermined sites is preferred due to the achievable alignment accuracy, device fabrication yield and emission point within the chip or array. But the process still involves growing the QDs on the sites, which need to be pre-patterned at a very fine scale, requiring nanolithography and nanoimprint techniques. Thus the QD growth process risks the integrity of the chip. Lithographic or ion beam structuring methods can also be used for creating precisely positioned QD structures for ultra-high volume manufacturing, but they increase the cost of the device significantly.

To address this, QuILT – Quantum Element Interposition by Laser Transfer – seeks to replace the expensive QD growth process and associated, expensive site pre-patterning by realising the QD or quantum element placement. The project’s solution will use laser-induced forward transfer (LIFT) of the selected semiconductor material, from a mechanically nano-positioned donor layer to the now simpler sites of a PIC or other photonic device, as it is being built on the silicon wafer substrate. The resulting technology will enable the customisation of a vast number of electro-photonic devices with added quantum emission capability. The ultimate goal, beyond QuiLT, is the construction of an on-chip-implanted QKD system.

Dr Panagiotis Chatzakos, Director of the Essex Innovation Centre, said: “In delivering this project, we are aiming to prove that our new technique for quantum element interposition utilising laser transfer, will turn what is currently a complex and costly step in semiconductor fabrication into a more optimised, timely and cost-effective process.” “By combining our specialist areas of knowledge and experience collaboratively: project partner PPL will construct an ultraviolet deposition chamber and develop process parameters for depositing chalcogenide quantum dots and nanoparticles onto precise positions of etched, waveguide structures on silicon wafers; and MSL will design and create masks for etching small waveguide and optical element features onto silicon oxide layers grown on silicon wafers, while will assess the effectiveness of the deposition method and the localisation of quantum elements in reference to waveguide structures on the silicon die, and undertake research on appropriate quantum entangled particle detection elements and electronics." "We are confident that the QuiLT solution will provide a viable new process for the quantum computing industry.”

The end-to-end process of building an effective consortium, collaborative working to hone the original technology concept and translate it into a persuasive proposal document, and managing the financial information and project plan, was supported by TWI’s Technology Innovation Management (TIM) team who also ensured the consortium’s competitive bid was targeted at the most appropriate grant funding stream. Since 2008, the TIM team has been instrumental in helping more than 1,100 partner organisations, including UK and European SMEs, RTOs and TWI Innovation Centres, to win £579m+ of funding for circa 415 collaborative projects.

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