CE47 - Technologies quantiques

Quantum control of an ultra-coherent mechanical resonator with a fluxonium qubit – MecaFlux

Submission summary

This project aims to measure and manipulate the quantum state of an ultracoherent macroscopic mechanical resonator by coupling it to a superconducting qubit. This type of resonator, oscillating in the MHz domain, and with a lifetime exceeding 1 minute, could be used to store quantum information on-chip, and to test quantum mechanics in an unprecedented regime where gravitational effects become relevant. The main technological barrier, identified by numerous groups around the world, consists in bridging the gap between the mechanical frequency and that of superconducting circuits, generally operating in the microwave domain. The original approach proposed in this project consists of using a "fluxonium qubit”. This superconducting circuit introduced by the group of M. Devoret presents a low-frequency qubit manifold whose coherence properties outperform all other superconducting qubit implementations. Opportunely, in the so-called “heavy-fluxonium” regime, the qubit frequency naturally matches that of the mechanical resonator at a few MHz, while the large capacitive shunt lends itself ideally to an electro-mechanical coupling scheme to the mechanical system. Finally, although the qubit-manifold lies well below the frequency range accessible with standard microwave components, the rich level structure of higher qubit excited states allows for its efficient readout, reset, and manipulation. In this project, we will demonstrate the strong coupling regime between the qubit and the mechanical resonator, and use this interaction to prepare the latter in highly non-classical states, such as Schrödinger-cat superpositions. In addition to immediate applications in the field of quantum information, the mass and frequency of the mechanical system used in this project will make it possible to test quantum mechanics in an unprecedented parameter regime, where several theoretical models predict that gravitational collapse might be the dominating decoherence mechanism.

Project coordinator

Monsieur Samuel Deléglise (Laboratoire Kastler Brossel)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


Inria de Paris Centre de Recherche Inria de Paris
LPENS Laboratoire de physique de l'ENS
LKB Laboratoire Kastler Brossel
SPEC Service de physique de l'état condensé

Help of the ANR 658,882 euros
Beginning and duration of the scientific project: September 2021 - 48 Months

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