PRESQUILE spin-photon chair

Five-year chair in experimental solid-state physics with a focus on semiconductor spin qubits coupled to microwave photons


The Quantum Photonics, Electronics and Engineering Laboratory (PHELIQS), a joint research unit of the CEA Fundamental Research Division in Grenoble (CEA-IRIG ) and Université Grenoble Alpes (UGA), is opening a 5-year chair position in experimental solid-state physics with a focus on semiconductor hole-spin qubits coupled to microwave photons.
Within PHELIQS, the LaTEQS team (LaTEQS) is currently developing a large panel of experimental approaches to quantum technologies, including hole-spin qubits in silicon and germanium. In this context, the successful candidate is expected to establish and lead a focused research effort on circuit quantum electrodynamics with hole spin-qubits. A single microwave photon in a superconducting cavity can act as quantum bus enabling long-distance entanglement between spin qubits. Therefore, the quantum mechanical interaction between spins and microwave photons may play a key role in the development of scalable spin-qubit architectures.
This research topic is part of the ambitious PRESQUILE project funded by the French “Plan quantique”, in which PHELIQS is deeply involved thanks to its expertise in silicon device technology, cryoelectronics, cryogenics, and nanofabrication at the Upstream Technological Platform (PTA). The successful candidate is expected to develop her/his own project in close synergy with the LaTEQS team, establish and manage research collaborations with academic and industrial partners, including other groups within CEA and outside. The candidate is expected to supervise the research activity of students and post-docs. Strong team spirit and leadership attitude are therefore required. The PRESQUILE grant will support the personnel and running costs associated to the chair.
Located in the French Alps and surrounded by a stunning natural environment, the international city of Grenoble hosts a rich scientific ecosystem formed by public research organizations (CEA , CNRS), Université Grenoble Alpes (UGA), Large Scale European Infrastructures (ESRF,ILL), and high-tech companies. Université Grenoble Alpes attracts a large number of students in a broad range of disciplines, including quantum technologies through its recently created Federation QuantAlps.
CEA is a French public research organization that stands at the crossroad between fundamental and applied research. PHELIQS is one of the 10 laboratories of the CEA Interdisciplinary Research Institute of Grenoble (CEA-IRIG), which gathers 1200 people in the fields of physics, chemistry, biology, health, and cryotechnologies.

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Master thesis and internships

Quantum thermodynamics in hybrid circuits


Quantum bits are the basic building blocks of future quantum processors. Among candidates as physical units carrying the quantum information (the qubits), hole spins in germanium have recently been spotted as very promising candidates, with the recent demonstration of two, and even four-qubits processors [1-2]. These spin qubits can be initialized, controlled and read, but all these operations are found extremely sensitive to temperature. In this master project, possibly followed by a PhD thesis, we propose to develop an innovative way to cool down locally germanium nano-structures below the base cryostat temperature, which could have a great impact on future design of Ge-based quantum processors. This will be achieved by placing a germanium nano-structure in contact with a superconductor. Indeed, such superconductor-semiconductor interface provides a very efficient way to cool down the semiconductor, by selective tunnel-out of hot electrons (Fig.1a). To fulfill this objective, a first approach will be to control the transparency of the superconductor/semiconductor interface [3]. The candidate will also develop strategies to measure temperature of the nano-structure, relying on proximity effect and Coulomb-blockade thermometry. She/he will be involved in the design and fabrication of the Ge/SiGe samples, and characterize them experimentally. This will include measurements in cryogenic environments using dilution refrigerators.

(a) Energy distribution of
a semiconductor / insulator /superconductor junction, in the coolingconfiguration. Hot electrons from the normal part can escape through the
barrier to the superconductor. Extracted from [3] b) Complex germanium nanostructure fabricated in the team, including two gate layers (red and blue),which define three different quantum dots.
(a) Energy distribution of a semiconductor / insulator /superconductor junction, in the coolingconfiguration. Hot electrons from the normal part can escape through the barrier to the superconductor. Extracted from [3]
b) Complex germanium nanostructure fabricated in the team, including two gate layers (red and blue),which define three different quantum dots.

[1]Hendricks et al, Nature (2020)
[2]Hendricks et al, Nature (2021)
[3]Giazotto et al, Rev. Mod. Phys (2006)


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Radio-Frequency Reflectometry for Si spin quantum bits


Si chip bonded for RF measurements Our group is working on silicon and germanium spin quantum bits. Recently we have demonstrated state-of-the-art performances for a hole spin quantum bit made with silicon-on-insulator CMOS technology, in collaboration with CEA-LETI [1]. We are also developing germanium based devices which are alternative promising candidates for a scalable quantum computing platform. During this master thesis project you will measure down to very low temperatures (below 4.2K) a new series of devices which feature very narrow channels, down to 25nm. Four P-type wafers have been processed with 2 different types of oxide and 2 different materials for the gate stack. These various flavors should allow to clarify the location where the first holes appear at very low temperature. Indeed we have inferred from previous studies and strong collaborations with a theory group at IRIG that the presence of TiN at the bottom of the gate stack favors the appearance of the first holes on the sides of the top gate and not right underneath, as expected. The availability of an alternative oxide from the usual thermal oxide shall also help as it changes the rounding of the nanowire, resulting in a different confinement potential. This experimental work will rely heavily on using (and improving) the reflectometry technique. With this scheme, we probe the resonance frequency in the 100s of MHz of the sample embedded in a tank circuit. This RF measurement is much more powerful than recording the drainsource current, especially below or near the threshold, which is the region of interest for the first carriers. The figure on the right shows an example of such measurements, highlighting the coupling regimes of two coupled quantum dots. The candidates should have a solid background in solid state physics and a taste for instrumentation. This project is a good start for a PhD in our laboratory in the field of spin qubits.

RF signature of different coupling regimes for 2 quantum dots,obtained at 400mK by varying the gate voltages driving each dot.


[1]Piot et al, arXiv:2201.08637(accepted for publication in Nature Nanotechnology) , (2022)




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Local study of superconductivity in Magic Angle Twisted Graphene Layers (MATBLG)




Atomically resolved STM image of twisted graphene layers. The short-range period is atomic and the long-range period corresponds to the moiré. Vb=100 mV, it=500 pA.



Stacking two graphene layers with a rotation between them creates a moiré which drastically modifies the Dirac cones. The Fermi velocity reduces for twist angles lower than 10°and even cancels around a magic value of 1.1°. Since electrons are no longer allowed to move, Coulomb energy becomes the relevant energy scale and drives the system twoards new collective states of matter such as correlated insulating behaviour, orbital magnetism or superconductivity as evidenced by recent experiments [1,2]. The detailed mechanisms for the emergence of these phases and their connection with the new band topology are still unclear. The aim of this project is to constrain the theoretical scenarios by providing new experimental measurements of MATBLG at the local scale using Scanning tunneling Microscopy and Spectroscopy (STM/STS). We have previously demonstrated that MATBGL are highly inhomogeneous owing to ubiquitous local relative strains between the layers (heterostrain) [2]. We will study the influence of these inhomogeneities on the strongly correlated phases. In addition, the local electronic properties such as the local superconducting energy gap will be correlated to the global ones such as the critical temperature by performing simultaneous transport measurement. The experiments will be performed using a milliKelvin STM operated by the joint STM group in Grenoble (Néel/CNRS and IRIG/CEA). Their analysis will be done in collaboration with theory groups in France and Europe.
Picture of the very low temperature STM.

We are looking for a motivated candidate with interest in experimental physics and a strong background in condensed matter physics who will be involved in all aspects of the research from the fabrication of samples to their measurements with state of the art very low temperature scanning tunneling microscope and the analysis of measurements.


[1]Y.Cao et al, Nature 556, 43 (2018)
[2]X.Lu et al, Nature 574, 653 (2019)
[3]F. Mesple et al, Phys. Rev. Lett. 127,126405 (2021)

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Magnetic bound states in 2D superconductors




Atomically resolved STM image of twisted graphene layers. The short-range period is atomic and the long-range period corresponds to the moiré. Vb=100 mV, it=500 pA.






The presence of a nanoscale magnetic scatterer (a single atom, a molecule, a quantum dot etc.) on the surface of a superconductor can lead to the emergence of magnetic bound states (MBS) with peculiar spatial and spectral properties within the superconducting gap [1]. These states can be topologically trivial (the case of so-called Shiba states) or not (predicted Majorana zero modes). The project aims at investigating MBS in two-dimensional (2D) superconductors where they can have a much longer spatial extension [2], a situation which has not been studied experimentally in novel 2D materials. We will use 2D superconductors like graphene in which superconductivity can be induced by proximity or NbSe2 in which superconductivity is unusual in the mono layer limit. First, experiments will aim at tracking the signatures of the MBS and possible topological superconductivity with high spatial and energetic resolution near single magnetic adsorbates. In a second step, using the larger spatial extension of MBS on 2D superconductors, we will couple two of these states to study Shiba molecular states or even Shiba bands in larger ensembles [3].


STM image of 2D superconductor NbSe2. Inset shows atomic resolution.Measured in Grenoble.

STM image of 2D superconductor NbSe2. Inset shows atomic resolution.Measured in Grenoble.




The two-dimensional superconductors will be prepared with the Molecular Beam Epitaxy facilities of the CEA/SPINTEC laboratory. MBS will be studied and manipulated with a milliKelvin STM operated by the joint STM group in Grenoble (Néel/CNRS and IRIG/CEA) and within a larger collaboration with the university of Berlin. Interpretation of the measurements will be performed in collaboration with theory groups. We are looking for a motivated candidate with a strong background in condensed matter physics, willing to work at the interface between surface physics and quantum transport. The candidate will be involved in the project from the preparation of superconducting substrates and magnetic nanostructures, by self-assembly or singleatom manipulation (see images) to low temperature scanning probe measurements and analysis and interpretation.


[1]A. Yazdani et al, Science 275, 1767 (1997)
[2]G. Ménard et al, Nature 11, 1013 (2015)
[3]L. Schneider et al, Nature Physics 17,943 (2021)

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Germanium heterostructure for quantum computing


Wired sample before cryogenic cooling Quantum computing (QC) is currently pushing further the frontier of information technology. Among other fields, solid-state spin qubits and superconducting qubits are promising research areas for QC. Recently our laboratory has developed a new platform for quantum devices based on heterostructures embedding a high mobility germanium hole quantum well. With these heterostructures, we have recently been able to demonstrate our ability to fabricate functional quantum dot devices and Josephson junctions. To further develop this platform, we are currently optimizing the heterostructure to decrease the interface defect density, hence increasing the mobility of the hole gas. In that prospect, we are looking for a talented and motivated Master student to design, fabricate and measure structures to probe the quality of the germanium quantum well. During the master project, you will collaborate on a daily basis with a lively team of three permanent researchers with two PostDocs and two PhD students and take part of an exciting adventure to make germanium the ideal platform for solid-state quantum computing. You will participate to the development of the samples that includes design, theory and nanofabrication done in our cleanroom facility. You will also learn to cool down samples to reach cryogenic temperatures. Finally, you will perform high magnetic field, highresolution low-noise measurements in these cryogenic environments using state-of-the-art setups down to 10mK. Your experimental results will be discussed and understood via theory models as well. This master project is expected to continue as a PhD thesis.






Shubnikov–de Haas oscillations in high-mobility germanium quanum well






[1]The germanium quantum information route, Scappucci, G, , Nat Rev Mater 6, 926–943(2021)


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Microwave resonators on Germanium HeteroStructures


Wired sample before cryogenic cooling Quantum computing (QC) is currently pushing further the frontier of information technology. Among other fields, solid-state spin qubits and superconducting qubits are promising research areas for QC1. Recently our laboratory has developed a new platform for quantum devices based on heterostructures embedding a high mobility hole quantum well. These quantum devices are on one-side Quantum dots, which can host future spin qubits, and on the other side Josephson junctions, which can be at the heart of future superconducting qubits. To further develop this platform we are currently developing microwave-superconducting circuit on this platform to allow future high frequency experiments. In that prospect, we are looking for a talented and motivated Master Student to fabricate and measure microwave resonators on Germanium HeteroStructures. During the master project, you will collaborate on a daily basis with a lively team of three permanent researchers with two PostDocs and two PhDs and take part of an exciting adventure to bring microwave photons available for germanium quantum dots and germanium Josephson junction. You will participate to the development of the samples that includes design, theory and nano-fabrication done in our cleanroom facility. You will also learn to cool down samples to reach cryogenic temperatures. Finally, you will perform RF measurements in these cryogenic environments using state-of-the-art RF setups down to 10mK. Your experimental results will be discussed and understood via theory models as well. This master project is expected to continue as a PhD thesis.






Two-qubit device in Germanium






[1]The germanium quantum information route, Scappucci, G, , Nat Rev Mater 6, 926–943(2021)


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Post-doc positions

Germanium-based qubits


A 3-year post-doctoral research position (f/m/d) is available at the LaTEQS laboratory of CEA in Grenoble.The experimental researcher will join an existing team (3PhDs,3staff, 3 staff researchers,2engineers) focusing on the development of novel quantumq electronics based on Ge/Si heterostructures.This emerging material,which embeds high-mobility mobilitymobility two-dimensionalhole gas,has been identified as a promising candidate for spin qubits and hybrid superconductor-semiconductor qubits [1]. Along this line, we have already obtained some first encouraging results, such as the demonstration of ballistic hole transport over long distances[2] and the realization of Josephson field-effect transistors and gate tunable SQUIDs[3].

Example of a two-layer gate strucuture defining a hole quantum dotvin a Ge / SiGe heterostructure.
Example of a two-layer gate structure defining a hole quantum dot in a Ge/SiGe heterostructure. This structure was fabricated in our cleanroom. Scale bar: 100nm

[1] G. Scrappuci, et al. Nature Reviews Materials 6, 926-943(2021)
[2] 2. R Mizokuchi , et al. Nanoletters 18, 4861-4865 (2018)
[3] F. Vigneau et al. Nanoletters 19, 1023-1027 (2019)


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