Electrons have a property called spin, and researchers at the University of Leeds are learning to control it—not just for faster electronics, but to build the basic units of a quantum computer. This matters because today’s computers process information as bits that are either 0 or 1. A quantum computer uses “qubits,” which can be both at once, potentially solving problems that are impossible for conventional machines. The challenge is that qubits are fragile and difficult to manipulate. The Leeds group is combining two hot fields—spintronics and quantum information—to tackle this. They will use exotic materials such as graphene, carbon nanotubes, and superconductors to create devices that can measure and control single electron spins, generate pure spin currents without electrical resistance, and produce entangled pairs of particles. If successful, this fundamental science could lay the groundwork for a working quantum computer. Such a machine would transform cryptography, drug discovery, and materials design—systems that quietly underpin modern life. The project is primarily curiosity-driven, but past fundamental work on spin and quantum mechanics led directly to technologies like MRI scanners and hard disk drives.
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The incorporation of electron spin into electronics is now known as spintronics. Our group at Leeds has recently expanded from two to four academics working on spintronics and this is an appropriate time to consider the longer term development of our activity. One of our new academics is an expert in lithographic techniques and superconductivity whilst the other specialises in carbon-based electronics. This development means that most of the interesting phenomena in spintronics now have some activity in Leeds. Quantum Information (QI) is the application of quantum mechanics to information processing with the long term objective of building a quantum computer. The idea is to exploit the property of a quantum system whereby all possible states are 'explored' simultaneously. The key to this exploitation is the control of the mixing of the quantum states or the 'entanglement' as it is known. One of the most basic and most controllable quantum two-level system is the spin, and hence there is the possibility of using solid-state spintronics for creating qubits, the basic QI unit.We are building a very close collaboration with five academics in the new Leeds QI theory group and we have some very interesting proposals to develop experimental work on the application of spintronics in QI. This project will study solid state systems with a view to learning how to manipulate the entanglement of states. We shall approach this problem by using our experience in spintronics to control and measure properties at the level of a single spin, to control and measure pure spin currents where there is no net flow of charge and hence no dissipation, and to apply these findings to further the understanding of quantum entanglement. Our proposal describes how we shall use some of the most exotic new materials such as graphene in devices contacted by ferromagnets and superconductors in different geometries; how we are using carbon nanotubes connected to superconductors to generate entangled pairs and spin polarised currents without the application of voltages. We shall develop single spin devices by embedding nanoparticles in insulators and use organic molecules to change the work function of metals and form single electron spin polarised emitters. We shall combine ferromagnets and superconductors in devices known as pi-Josephson junctions to develop spin-based qubits. This application is unique in seeking to combine two of the topics attracting huge attention globally: spintronics and quantum information.
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