Vibrating carbon nanotubes for probing quantum systems at the mesoscale

Project Information

MesoPhone

Grant agreement ID: 818751

DOI

10.3030/818751

Project closed

EC signature date 29 January 2019

Start date 1 March 2019

End date 28 February 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 748 271,00

EU contribution

€ 2 748 271,00

Coordinated by

UNIVERSITY OF LANCASTER
United Kingdom

Periodic Reporting for period 4 - MesoPhone (Vibrating carbon nanotubes for probing quantum systems at the mesoscale)

Reporting period: 2023-09-01 to 2025-02-28

Summary of the context and overall objectives of the project

Many fascinating quantum behaviours occur on a scale that is intermediate between individual particles and large ensembles. It is on this mesoscopic scale that collective properties, including quantum decoherence, start to emerge.
This project will use vibrating carbon nanotubes – like guitar strings just a micrometre long – as mechanical probes in this intermediate regime. Nanotubes are ideal to explore this region experimentally, because they can be isolated from thermal noise; they are deflected by tiny forces; and they are small enough that quantum jitter significantly affects their behaviour. To take advantage of these properties, I will integrate nanotube resonators into electromechanical circuits that allow sensitive measurements at very low temperature.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have installed two new refrigerators that can reach the very low temperatures required for this project, and instrumented them with sensitive electronic amplifiers to detect nanotube vibrations. Our main scientific discoveries so far have been:
- We have shown how to use a superconducting amplifier to measure very small radio-frequency signals.
- This enabled us to measure self-generated oscillations of a vibrating nanotube, work that was covered in newspapers including the i, Spiegel, and Guitar World.
- We have shown how an artificially intelligent machine can learn the behaviour of a nanoscale electronic device and use this information to optimise it for a purpose determined by the human experimenter.
- We have used a nanomechanical resonator (in this case a silicon nitride drum) to study the thermodynamic cost of timekeeping.
- We have used a single-electron transistor as an electronic refrigerator operating inside a cryostat.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The question addressed during this project was: How does quantum mechanics affect the behaviour of mesoscopic moving objects, and how can we exploit any such effects?
This is important for society because many quantum technologies operate in this regime. Examples include new kinds of microscope that work by measuring tiny forces, and new kinds of amplifier that can detect tiny electrical signals. The question is also interesting from a pure scientific point of view, because the mesoscopic regime is where everyday classical behaviour starts to emerge from the quantum behaviour of individual particles.
To address this question, we have developed new kinds of electromechanical device made from vibrating carbon nanotubes. Our discoveries have included new ways to measure tiny motion using superconducting amplifiers, a new mechanism for exciting this motion due to the tunnelling of individual electrons, and a proposal to create large quantum superpositions by incorporating carbon nanotubes into superconducting qubits.

A vibrating carbon nanotube