**A post-doctoral position is open at the Interdisciplinary Research Institute of Grenoble (IRIG) of the CEA Grenoble (France) on the theory and modeling of silicon/germanium spin quantum bits (qubits). The selected candidate is expected to start in July 2022 (or later), for up to three years.**

**Global context:**

Silicon/Germanium spin qubits have attracted increasing attention and have made outstanding progress in the recent years. In these devices, the elementary information is stored as a coherent superposition of the spin states of an electron in a Si/SiGe heterostructure, or of a hole in a Ge/SiGe heterostructure. These spins can be manipulated electrically owing to the intrinsic (or to a synthetic) spin-orbit coupling, and get entangled through exchange interactions, allowing for the implementation of a variety of one- and two-qubit gates required for quantum computing and simulation. Si/Ge heterostructures hold various records in semiconductor spin qubit technologies [1, 2], as they provide very clean epitaxial interfaces, and can be made free of nuclear spins that would interfere with the electron or hole spins.

**Local context:**

Grenoble is developing an original spin qubits platform based on the “silicon-on-insulator” (SOI) technology, and is now moving forward to new Si/SiGe (electrons) and Ge/SiGe (holes) routes, in the context of a national initiative for quantum technologies. This activity is carried out by a consortium bringing together three of the main laboratories of Grenoble, CEA/IRIG, CEA/LETI, and CNRS/Néel. On this SOI platform, Grenoble has for example demonstrated the electrical manipulation of a single electron spin [3] as well as the first hole spin qubit [4], and recently achieved record hole spin lifetimes [5].

It is essential to support the development of these advanced quantum technologies with state-of-the-art theory and modeling. For that purpose, CEA/IRIG is actively developing the “TB_Sim” code. TB_Sim is able to describe very realistic qubit structures down to the atomic scale if needed using atomistic tight-binding and multi-bands **k.p** models for the electronic structure of the materials. Using TB_Sim, CEA has recently investigated various aspects of the physics of spin qubits, in tight collaboration with the experimental groups in Grenoble and with the partners of CEA in Europe [3, 5-12].

**Objectives of this position:**

**The aims of this position are to strengthen our understanding and support the development of electron and hole spin qubits based on Si/Ge heterostructures through analytical modeling as well as advanced numerical simulation with TB_Sim.** Topics of interests include:

- Structural and electronic properties of Si/SiGe and Ge/SiGe dots,
- Spin manipulation & readout in electron and hole spin qubits (intrinsic & synthetic spin-orbit fields),
- Exchange interactions in 1D and 2D arrays of qubits and operation of multi-qubit gates,
- Sensitivity to noise (decoherence) and disorder (variability),
- Interactions of spins with other quasiparticles and long-range entanglement (spin-photon coupling, …).

The selected candidate will join a lively project bringing together > 50 people with comprehensive expertise covering the design, fabrication, characterization and modeling of spin qubits, as well as related disciplines (cryoelectronics, quantum algorithms and quantum error correction, ...).

**How to apply ?**

The candidate should send her/his CV to Yann-Michel Niquet (yniquet@cea.fr) and Michele Filippone (michele.filippone@cea.fr), with a list of publications, a motivation letter with a summary of past accomplishments, and arrange for two recommendation letters. The position is open until filled.

Required qualifications: The candidate must have a PhD in Quantum, Condensed Matter or Solid-State Physics (or related topics).

**References:**

[1] *A four-qubit germanium quantum processor*, N. W. Hendrickx, W. I. L. Lawrie, M. Russ, F. van Riggelen, S. L. de Snoo, R. N. Schouten, A. Sammak, G. Scappucci and M. Veldhorst, Nature **591**, 580 (2021).

[2] *Universal control of a six-qubit quantum processor in silicon*, S. G. J. Philips, M. T. Mądzik, S. V. Amitonov, S. L. de Snoo, M. Russ, N. Kalhor, C. Volk, W. I. L. Lawrie, D. Brousse, L. Tryputen, B. Paquelet Wuetz, A. Sammak, M. Veldhorst, G. Scappucci, and L. M. K. Vandersypen, arXiv: 2202.09252.

[3] *Electrically driven electron spin resonance mediated by spin–valley–orbit coupling in a silicon quantum dot*, A. Corna, L. Bourdet, R. Maurand, A. Crippa, D. Kotekar-Patil, H. Bohuslavskyi, R. Laviéville, L. Hutin, S. Barraud, X. Jehl, M. Vinet, S. de Franceschi, Y.-M. Niquet and M. Sanquer, npj Quantum Information **4**, 6 (2018).

[4] *A CMOS silicon spin qubit*, R. Maurand, X. Jehl, D. Kotekar-Patil, A. Corna, H. Bohuslavskyi, R. Laviéville, L. Hutin, S. Barraud, M. Vinet, M. Sanquer and S. de Franceschi, Nature Communications **7**, 13575 (2016).

[5] *A single hole spin with enhanced coherence in natural silicon*, N. Piot, B. Brun, V. Schmitt, S. Zihlmann, V. P. Michal, A. Apra, J. C. Abadillo-Uriel, X. Jehl, B. Bertrand, H. Niebojewski, L. Hutin, M. Vinet, M. Urdampilleta, T. Meunier, Y.-M. Niquet, R. Maurand and S. De Franceschi, arXiv: 2201.08637.

[6] *All-electrical manipulation of silicon spin qubits with tunable spin-valley mixing*, L. Bourdet and Y.-M. Niquet, Physical Review B **97**, 155433 (2018).

[7] *Electrical spin driving by g-matrix modulation in spin-orbit qubits*, A. Crippa, R. Maurand, L. Bourdet, D. Kotekar-Patil, A. Amisse, X. Jehl, M. Sanquer, R. Laviéville, H. Bohuslavskyi, L. Hutin, S. Barraud, M. Vinet, Y.-M. Niquet and S. de Franceschi, Physical Review Letters **120**, 137702 (2018).

[8] *Electrical manipulation of semiconductor spin qubits within the g-matrix formalism*, B. Venitucci, L. Bourdet, D. Pouzada and Y.-M. Niquet, Physical Review B **98**, 155319 (2018).

[9] *Longitudinal and transverse electric field manipulation of hole spin-orbit qubits in one-dimensional channels*, V. P. Michal, B. Venitucci and Y.-M. Niquet, Physical Review B **103**, 045305 (2021).

[10] *A Spin Quintet in a Silicon Double Quantum Dot: Spin Blockade and Relaxation*, T. Lundberg, J. Li, H. Hutin, B. Bertrand, D. J. Ibberson, C.-M. Lee, D. J. Niegemann, M. Urdampilleta, N. Stelmashenko, T. Meunier, Jason W. A. Robinson, L. Ibberson, M. Vinet, Y.-M. Niquet and M. F. Gonzalez-Zalba, Physical Review X **10**, 041010 (2020).

[11] *Two-body Wigner molecularization in asymmetric quantum dot spin qubits*, J.-C. Abadillo-Uriel, B. Martinez, M. Filippone and Y.-M. Niquet, Physical Review B **104**, 195305 (2021).

[12] *Variability of electron and hole spin qubits due to interface roughness and charge traps*, B. Martinez and Y.-M. Niquet, Physical Review Applied **17**, 024022 (2022).

**Additional informations about the laboratory:**

http://www.cea.fr/drf/irig/english/Pages/Departments/DPhy.aspx

http://www.researchgate.net/profile/Yann-Michel_Niquet

http://scholar.google.fr/citations?user=h02ymwoAAAAJ

The group responsible for spin qubits modeling now includes two permanent researchers (Y.-M. Niquet, M. Filippone), two PhD students and three postdocs.

**More about Grenoble and its surroundings:**

http://www.isere-tourism.com/