Solid-state spins in an optical cavity

Context. An optically-active solid-state spin, for instance the spin associated with the NV centre in diamond, is a resource for creating spin-photon entangled pairs. In principle, this allows two remote spins to be entangled – the photons act as the entangling “glue”. In practice, the conditions which must be satisfied are rather stringent and the spin-spin entangling rates are presently too low to be useful in any quantum technology application. One key bottleneck is the low probability of creating a photon without an accompanying phonon in the solid-state lattice. This probability is not fixed: it can be increased in an optical cavity tuned to the correct frequency, the so-called zero-phonon line (ZPL). Theory predicts that even a modest cavity will do the job.
We are attempting to enhance the creation of phonon-free single photons by embedding NV centres in diamond in a tunable micro-cavity. Basic functionality has been established [1]. The ultimate goal is to create spin-spin entanglements at useful rates. A number of challenges have to be overcome. The materials processing must be improved in order to create optically-coherent NV centres in thin diamond-membranes. Quantum optics-based techniques must be used to quantify the properties of the photons: their purity and indistinguishability. Spin manipulation must be combined with the cavity setup. Techniques must be established to tune remote NV centres into resonance with each other. The project will offer experience in all these fields, along with possibilities to explore the application of the same cavity structure to other solid-state systems, for instance semiconductor quantum dots.

[1] Daniel Riedel, Immo Söllner, Brendan J. Shields, Sebastian Starosielec, Patrick Appel, Elke Neu, Patrick Maletinsky, and Richard J. Warburton, Phys. Rev. X 7, 031040 (2017)

Supervisor: Prof. Richard Warburton

Eligibility criteria and requirements
We are looking for a highly motivated experimentalist to join our groups at the University of Basel in Switzerland. You should hold a master’s degree in physics (or equivalent) and ideally have prior experience in either solid-state physics or quantum optics. You will work in an international team of 2-4 people on a cutting edge experimental setup. Our group is part of the Swiss national research centre in Quantum Science and Technology (QSIT), the Swiss Nanoscience Institute (SNI), as well as several European projects.

QUSTEC programme follows MSCA eligibility criteria: Required level of experience is ‘Early Stage Researcher’ according to the definition in the work programme of the 2018-2020 Marie Skłodowska-Curie actions: Applicants must, at the date of the respective call deadline of QUSTEC, be in the first four years (full-time equivalent research experience) of their research careers and have not yet been awarded a doctoral degree. Mobility criterion: The applicants must not have resided or carried out their main activity (work, studies, etc.) in the country of the future host organisation for more than 12 months in the 3 years immediately before the call deadline of QUSTEC. Short stays such as holidays are not taken into account. For refugees under the Geneva Convention, the refugee procedure (i.e. before refugee status is conferred) will not be counted as a period of residence/activity in the country of the host organisation.

Application procedure:
The proposed PhD position is part of the QUSTEC doctoral programme, funded by the MSCA-COFUND scheme, coordinated by Eucor – The European Campus, and implemented by Eucor partner institutions (University of Basel, University of Freiburg, University of Strasbourg and the Karlsruhe Institute of Technology), which are joined by IBM-Research in Zurich, and WMI in Munich. The complete description of the programme as well as the full list of research topics can be found on the project website. Candidates are encouraged to indicate two additional research topics that they are interested in, in addition to the selected PhD offer, from the list of available topics that can be found on the programme website.
Please, submit your application exclusively via an electronic submission system.
The deadline for applications is September 30, 2020 at 17.00 (Brussels time)

Before submitting the application, please contact the scientific supervisors (obligatory). For any other issues, please address your request to the programme coordinator (contact details can be found in the Guide for applicants).

Working conditions: All PhD candidates will be employed under a 4-years full-time PhD contract following the national regulations.