Superconducting carbon nanotube quantum circuits for nanomechanical experiments

Context: The last two decades have seen fast progress in the research field of nano-mechanical resonators [1], enabling to use these systems to study quantum mechanic at the scale of a single quanta. The recent advances in this field such as Schrödinger cat mechanical states [2] or entanglement between distinct resonators [3,4], offer great promise in the context of quantum computing. Among the various physical implementations of nano-mechanical resonators, a carbon nanotube is a very attractive candidate. Thanks to their small dimensions (diameter of 1-4nm) they possess very high resonance frequencies (from 50MHz to few GHz), and very large quality factors (up to few millions). In our group we recently developed a unique nano-assembly technique [5] allowing to fabricate state of the art quantum circuit based on suspended carbon nanotubes.

PhD subject: We propose to study the interaction between mechanical and electronic degrees of freedom using a Superconducting Quantum Interference Device (SQUID) based on a single suspended carbon nanotube. The project can evolve toward two main directions. The first one aims at observing and generating mechanical quantum states of the carbon nanotube such as Schrödinger cat. The other direction focuses on the study of the dynamics of a single molecular magnet [6] using the nanotube-SQUID as an ultra-sensitive magnetometer.

Work plan/Skills: A large part of the project is the measurement of the circuit. It will begin with the quantum transport characterization of the SQUID circuit using low-noise measurement techniques. The nanomechanics will also be probed with our microwave measurements setup. At a lower degree, the project will also contain the nano-fabrication of the circuit (clean-room techniques, carbon nanotube nano-assembling). According to the taste of the applicant, the project can also include some nanofabrication developments or simulations of the experiment.


[1] Mesoscopic physics of nanomechanical systems A. Bachtold, et al., RMP (2022).
[2] Schrödinger cat states of a 16-microgram mechanical oscillator. M. Bild, et al., Science (2023)
[3] Quantum mechanics–free subsystem with mechanical oscillators. L. Mercier de Lépinay et al., Science (2021)
[4] Direct observation of deterministic macroscopic entanglement. S. Kotler et al., Science (2021)
[5] Nano-assembled open quantum dot nanotube devices. T. Althuon et. al, submitted (2023)
[6] Quantum Einstein-de Haas effect. M. Ganzhorn, et al., Nature Communication (2016)