Multiplexed Quantum Integrated Circuits

The low-temperature multiplexer for quantum devices has allowed competing theories regarding quantum transport in interacting low-dimensional systems to be tested against experiment and because of the large numbers of devices that can be tested at once, a statistical approach to quantum nano-device physics discovery can be used. We induced superconductivity in two-dimensional electron gases and are searching for Majorana fermions. In this project, we want to proceed on several fronts, all using integrated circuits of split-gate transistors, to explore new physics, new technology and new electronics. This project will be supplemented (by other local projects and by the input from others using our facilities) so that most of the following topics will be pursued over the next three years: (* = core part of this project)

1. A gigahertz multiplexer*
2. Superconducting/semiconducting integrated circuits including topological insulator material addressed using the multiplexer*
3. Nanowire integrated circuits coupled to superconductors for investigating how robust Majorana modes are and exploring whether they could be reliably used for quantum technology*
4. Independent biasing through specific charge storage on each gate
5. Nanoscale multiplexer
6. A voltage camera circuit on the micron-scale
7. Multiplexers with induced 2DEGs to reduce fluctuations*
8. Single electron pumping in quantum dots in parallel to provide high current high accuracy pumps for a current standard*
9. Setting up a facility for external users*

This project will develop techniques that will allow hundreds of quantum nano-devices to be measured during the time that previously only one two could have been studied. Quantum nanodevices, when measured at low temperatures of a few kelvins above absolute zero, can show exotic quantum behaviour especially when two different materials are coupled together. The electrons in these systems can couple in new ways to behave, for example, like a new quasi-particle called a Majorana Fermion. It has been proposed that these Majorana Fermion quasi-particles can be used for quantum computing applications, but they are hard to observe, and the best conditions for observing them and manipulating them are only just being discovered. The multiplexer that will be used in this grant will allow hundreds of lightly different shaped devices to be made and tested to find and optimise how to robustly produce Majorana particles two different material systems. This will be very valuable to those working in quantum technology in this area. There will be a very large data set produced that those working in solid state theory can access to test their ideas on.
The development of a fast way to test multiple quantum devices will be of value to those who want to develop quantum technologies based on solid-state systems as we will develop data on how reliable and reproducible the physics we observe is.
In the long run, this research could help in the faster development of solid-state based quantum technology or will provide important information regarding a pathway to that goal. A quantum computer could, when developed, be used for fast materials discovery as such a computer would be ideally suited to model the quantum bonding found in new material systems. The discovery of new materials can then have an important impact on many areas, from energy generation and distribution to battery technology or biomedical application.