Research objectives
The goal of this thesis is to prepare a mechanical resonator in a non-Gaussian quantum state by coupling a mechanical degree of freedom to the internal state of a superconducting qubit, the elementary building block of current quantum computers. Bringing a massive object in a state that cannot be described by a positive Wigner function is an important prerequisite to explore new physics beyond standard decoherence mechanisms, as well as an important resource in quantum information. Mechanical resonators are for instance very good candidates for the realization of on-chip quantum memories. They can also be used to transduce quantum information in optical photons by coupling them to a high-finesse cavity, hence realizing a room-temperature link between remote superconducting quantum computers.

We have recently developed an electromechanical system able to bring a low-loss optomechanical membrane close to its quantum ground state by coupling it to the microwave field stored inside a superconducting resonator. This optomechanical interaction has been already used to prepare a mechanical resonator in a squeezed state [1], or to entangle the mechanical and electromagnetic degrees of freedom [2]. We will combine these resources with a single microwave photon-detector developed in collaboration with the LPA (ENS) and Quantronics (CEA-Saclay) groups to herald the preparation of non-classical states such as Fock state or Schrödinger-cat states by phonon-subtraction techniques [3]. This approach is largely insensitive to photon losses and as such, lends itself well to a modular architecture where the various elements are optimized separately and connected by standard RF connectors.
As part of the OMT-ETN network [4], the Optomechanics and Quantum Measurements group offers the possibility for PhD students to attend regular training workshops across Europe on various aspects of quantum optomechanics and quantum technologies.
Methods and techniques: The Optomechanics and Quantum Measurements group at Laboratoire Kastler Brossel has a unique expertise to perform such a project, with a pioneering experience in quantum-limited measurements in the microwave, optical, and mechanical domains. Cleanroom facilities with the required knowledge and equipments are fully available within Sorbonne Université and ENS. The project will be developed in a new cryogenic platform dedicated to microwave quantum experiments.

[1] Pirkkalainen et al. “Squeezing of Quantum Noise of Motion in a Micromechanical Resonator.” Phys. Rev. Lett. 115, 24, 243601 (2015).

[2] Palomaki et al. “Entangling Mechanical Motion with Microwave Fields.” Science 710 (2013).

[3] Ourjoumtsev, et al. “Generating optical Schrödinger kittens for quantum information processing.” Nature, 448 (7155), 784 (2007).

[4] http://www.omt-etn.net/

Job requirements
Interested candidates possessing fluency in English and a Master’s degree in Physics are encouraged to apply. Experience in quantum optics/nanomechanics/atomic and molecular physics is appreciated.

Information and application
For more detailed information about the position, please contact Dr. S. Deléglise (deleglise@lkb.upmc.fr).
Please send your application (including the contact information of the candidate, a CV, copies of transcripts/grade-sheets, the contact information of one or more references, as well as a copy of the Master’s thesis and (p)reprints of prior publications, if available) by e-mail.