Event Details

Condensed Matter seminar

As we gain ever-greater control of materials on a very small scale, so a new world of possibilities opens to be studied for their scientific interest and harnessed for their technological benefits. Nanoscale structures must be understood in terms of the positions of individual atoms and electrons, and the behaviour of individual quantum states. I shall introduce some of the remarkable collaborations which I enjoy with colleagues at Lancaster University.

We can take a single molecule, attach two wires to it, and use it as the active element in a transistor with graphene electrodes.[1] If we heat one end of the molecule more than the other, we can measure the resulting thermoelectric effect, and compare it directly with theoretical predictions.[2] In a similar but slightly larger device we can use a suspended carbon nanotube as a tiny guitar string,[3] and thereby investigate how thermodynamics applies to a single object in which information could play a measurable entropic role.[4] A vibrating membrane has enabled us to demonstrate the thermodynamic cost of timekeeping within an order of magnitude of the theoretical limit. [5]

If you place a single nitrogen atom in a fullerene carbon cage, it can behave almost like an isolated atom.[6] We have been able to find the clock transition in this species, which could form the basis of a solid state molecular atomic clock.[7] A carbon nanotube connected to a Pd/Al bilayer can form a superconducting qubit with strong dispersive coupling to a resonator,[8] and can be characterised by radio-frequency reflectometry.[9] A basic challenge in quantum computing is to tune and characterise qubits on an ever-expanding scale.[10] We have developed machine learning methods for quantum technologies, which are able to learn how to do this more efficiently than even experienced humans. [11]

As scientists we have the responsibility and the privilege of advocating the responsible use of the progress to which we contribute. This calls for insight from science and wisdom from other disciplines to learn how together we can seek to promote human flourishing in times which seem to be increasingly subject to uncertainty.[12]

[1] Charge transport through extended molecular wires with strongly correlated electrons. Chemical Science 12, 11211-11129 (2021)

[2] Field-effect control of graphene−fullerene thermoelectric nanodevices. Nano Lett. 17, 7055-7061 (2017)

[3] A coherent nanomechanical oscillator driven by single-electron tunnelling. Nature Physics 16,75-82 (2019)

[4] Ultrastrong coupling between electron tunneling and mechanical motion. arXiv:2103.15219

[5] Measuring the thermodynamic cost of timekeeping. Phys. Rev. X 11, 021029 (2021)

[6] Implementation of quantum level addressability and geometric phase manipulation in aligned endohedral fullerene qudits. Angew. Chem. 2022, e202115263 (2022)

[7] Spin resonance clock transition of the endohedral fullerene 15N@C60. Phys. Rev. Lett. 119, 140801 (2017)

[8] Circuit quantum electrodynamics with carbon-nanotube-based superconducting quantum circuits. Phys. Rev. Appl. 15, 064050 (2021)

[9] 648. Radio-frequency characterization of a supercurrent transistor made from a carbon nanotube. Mater. Quantum Technol. 1, 035003 (2021) [10] Efficiently measuring a quantum device using machine learning. npj Quantum Information 5, 79 (2019)

[11] Machine learning enables completely automatic tuning of a quantum device faster than human experts. Nat. Commun. 11, 4161 (2020)

[12] Human Flourishing: Scientific insight and spiritual wisdom in uncertain times. Oxford University Press (2021)

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