EPSRC CDT in Metamaterials (Robert Brown PhD Studentship): Probing Mechanics in Quantum Mechanics – Josephson Nano-resonator Metamaterials

University of Exeter - Centre of Doctoral Training in Metamaterials (XM2)

Statement of Research

Joint supervisors: Prof Saverio RussoDr Eros Mariani
External sponsor: Robert Brown (Diamond Jubilee Doctoral Scholarship Match Fund)
Industrial partner: National Physical Laboratory (NPL)

Synopsis – Quantum mechanics has been a main cornerstone of physics, and of science in general, for the last century. And yet, for all this time the word “mechanics” – commonly associated to macroscopic moving objects – hardly played any role in the quantum description of the world. Only few years ago scientists started investigating the interplay between the quantum properties of electrons and of mechanical degrees of freedom in nano-electromechanical systems (NEMSs).
In this project we will explore experimentally and theoretically the quantum behaviour of NEMSs in innovative metamaterials based on mechanical oscillators suspended between two superconductors – the Josephson junction nano-resonators. The remarkable sharpness of the resonator oscillations, further increased by the absence of dissipation induced by the superconductors, will turn these devices into force and mass sensors with unprecedented sensitivity, to be exploited in sensors and RF transducers of the next generation.

Project description – A conventional Josephson junction is constituted by an insulator or a normal metal sandwiched between two superconductors. The Josephson effect manifests itself as a dissipationless electronic current (a super-current) flowing through the system despite the normal metal or insulating junction.
Here we will explore for the first time the interplay between electronic supercurrents and mechanical oscillations in arrays of Josephson junction nano-resonators. Starting with a single suspended junction – based on graphene or other atomically thin materials – we will exploit supercurrents to controllably amplify mechanical oscillations in the resonator and unveil their signatures on the very nature of the Josephson effect.
In the second stage of the project we will explore pairs of Josephson nano-resonators coupled via a superconducting loop in a superconducting quantum interference device (SQUID). The supercurrents in the SQUID mediate a coupling between the two resonators, yielding quantum entanglement between macroscopic mechanical oscillators. This unprecedented result will open novel scenarios in the context of quantum computation, leading to macroscopic mechanical qubits with electrical control and read-out.
The final stage of the project will focus on quantum metamaterials constituted by arrays of Josephson junction nano-resonators, with the aim of controlling and detecting registers of mechanical qubits.

A world-leading research challenge – This pioneering project targets a novel area of research on Josephson junction NEMSs. Only recently few groups worldwide realised Josephson junctions or SQUIDs with suspended components. So far still no one reported the controllable amplification of resonator oscillations and their signatures in electronic quantum transport. The track record of the two supervisors and of their groups, together with an innovative activation setup, will be key to guarantee the success of this challenging project.

The role of the CDT – This project naturally fits three themes of the metamaterials CDT: a) Graphene and other 2D Materials, b) Nanomaterials and nanocomposites, and c) Quantum Metamaterials. The student in this project will benefit from the broad range of activities on metamaterials at the Exeter CDT. In particular, the top-notch training offered to CDT students will complement the technical skills acquired in the project and diversify the student’s strengths in view of a career in academia or in the industrial sector.

This studentship is part of the Centre of Doctoral Training in Metamaterials. Please see all fully funded opportunities.

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South West England