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Details of Grant 

EPSRC Reference: EP/Y020448/1
Title: Atomic-scale Dopant Devices in Silicon for Quantum Technologies
Principal Investigator: Curson, Professor NJ
Other Investigators:
Researcher Co-Investigators:
Project Partners:
IKZ -Leibniz Institute of Crystal Growth
Department: London Centre for Nanotechnology
Organisation: UCL
Scheme: Overseas Travel Grants (OTGS)
Starts: 01 December 2023 Ends: 30 April 2024 Value (£): 25,017
EPSRC Research Topic Classifications:
Electronic Devices & Subsys. Quantum Optics & Information
EPSRC Industrial Sector Classifications:
Communications Electronics
Related Grants:
Panel History:  
Summary on Grant Application Form
Quantum computing has captured the imagination of academics, industrialists and the general public alike, due to its potential to solve currently intractable computational problems and its origin in the 'spooky physics' of quantum mechanics. Whereas the computers of today store and process information in the form of 'bits' which can be either a 0 or a 1, quantum computers instead process quantum bits (qubits), which can be a 0 or a 1, or any combination of the two i.e. the qubit can exist in a superposition state. It is this spooky quantum property, along with another called entanglement, that gives quantum computers their amazing capabilities.

There are many fundamentally different ways in which a quantum computer can be realised, however it is particularly appealing to make it in the solid-state, much like an integrated circuit. Spin qubits in silicon are particularly good as they are small, easy to manipulate with electric and magnetic fields and that their fabrication uses cleanroom technology compatible with the semiconductor industry. There are two types of spin qubits. The first is based on quantum dots (QDs), which work on a similar principle to that of metal-oxide-semiconductor field effect transistors (MOSFETs), in that a potential is applied to a surface gate electrode in order to attract carriers to an interface. Through manipulation of the local electric potential around the dot, the dot is depleted of all electrons except one, and this electron acts as a spin qubit. The other type of spin qubit can be formed when an individual dopant atom, such as phosphorus (P) or arsenic (As), is embedded in silicon. The dopant atom has one extra outer-shell electron compared with its silicon neighbours, and when that electron orbits the dopant nucleus, it also acts as a spin qubit. The advantage of dopant qubits is that they have extremely long coherence times, i.e. they can retain quantum information for a long time before that information is lost to their local environment. The STM device fabrication group at UCL specialises in positioning dopant atoms at atomically precise locations in the silicon lattice and has discovered that by using As instead of P, yield of dopant placement increases to 100%. For scaling up to many qubits, this is revolutionary.

The purpose of this travel grant is for Prof. Curson to create links, and initiate projects, that will exploit the recent breakthrough that his group has made. In the group of Profs. Dzurak and Morello at the University of New South Wales (UNSW) in Australia, he will explore the possibility of combining the two types of qubits mentioned above. The dopant qubits can act as long-lived quantum 'memory', while the quantum dot qubits can be used to perform fast manipulation and readout. Creating a quantum computing architecture to exploit this qubit combination would be very exciting, but also very challenging, so initial ideas for a research programme will be formulated. A separate idea would involve the implementation of the elegant UNSW technique recently developed to electrically control the nuclear spin of a single antimony dopant, randomly implanted in silicon, but for an arsenic atom positioned at a precise location by the laboratory at UCL.

Professor Curson will also spend some time in Berlin, hosted at the Leibniz Institute for Crystal Growth (IKZ). He will collaborate with a research group working on the enrichment of silicon and germanium and its growth by molecular beam epitaxy. New ideas for utilising these materials for quantum technologies will be developed. Further, collaborations will be initiate around the use of dopants as spin qubits in germanium. This is a completely untouched area of research and of great interest to the PI and colleagues at UCL. Expertise at IKZ, and also at the Leibniz Institute for High Performance Microelectronics (IHP), will be invaluable to develop science and engineering approaches for qubit fabrication and measurement.
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