capacity, and coupling strength. Ensembles of electron spins for microwave quantum state storage combines three advantages. 1) They can offer storage times longer by two orders of magnitude compared to superconducting qubits [2]. 2) They have a small footprint, and are compatible with superconducting qubits. 3) Protocols exist for storing multiple states into the same device, and can be used to reduce the number of required qubits for quantum algorithm [3]. However, current spin ensemble memories suffer from low storage efficiency (<10%) due to a fundamental trade-off: high spin concentration enhances coupling to microwave circuits but reduces coherence.
To overcome this, we propose exploring a novel spin system—ytterbium atoms embedded in CaWO₄—which maintains state-of-the-art coherence at much higher concentrations than previously studied systems [4]. Additionally, this system can operate at zero magnetic field, making it highly compatible with superconducting qubits. This compatibility opens the door to on-chip integration of spin ensembles and superconducting qubits, similar to early proof-of-concept demonstrations [5].
The project will center around two milestones. We will first test a new deposition technique to strengthen the spin-resonator coupling, and benchmark the storage of classical and then quantum fields inside the spin ensemble.
The PhD project will take place in collaboration with a team in ChimieTech synthesizing the CaWO4 crystals, and PStash, a nascent start-up company based in Paris. The PhD will be funded through an industrial fellowship, and will be realized in Lyon at the beginning with an option to join the experimental effort in Paris at a later stage.
[1] H. J. Kimble, Nature 2008 ; D. Thaker et al., ISCA 2006 ; Zaiser et al., Nature Comm 2016
[2] G. Wolfowicz et al., Nature nano (2013).
[3] V. Damon et al., New J. Phys. 13 (2011).
[4] A. Tiranov, arXiv:2504.01592
[5] Kubo et al., PRL 2011
Where to apply
E-mail: audrey.bienfait@ens-lyon.fr
Requirements
Research Field: Physics » Quantum mechanics
Education Level: Master Degree or equivalent
Languages: ENGLISH
Level: Excellent
Research Field: Physics » Quantum mechanics, Physics » Solid state physics
Years of Research Experience: None
Additional Information
Selection process
Please send an email with your CV, transcripts, and a short paragraph stating why you are interested in the offer and any relevant experience.
Work Location(s)
Number of offers available: 1
Company/Institute: ENS Lyon
Country: France
City: Lyon
