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Subject of the postdoc

Modeling of silicon/germanium spin qubits

Published on 28 September 2022
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 early 2023, for up to three years.

Global context
Silicon/Germanium spin qubits have attracted increasing attention and have made outstanding progress in the past two 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.

Fig. 1: TB_Sim model of a SOI device with a silicon channel (in red) controlled by four overlapping gates (in gray). The channel is 100 nm wide, 18 nm thick, and is connected to overgrown reservoirs of charges on both sides. The model includes a realistic disorder (charge traps and roughness, visible at the surface of the channel). An isodensity surface of the ground-state wave function of a hole trapped under the third (semi-transparent) gate, computed with a 6 bands k.p model, is plotted in yellow.

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] and spin-photon coupling [6].

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 (see Fig. 1). 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, 5-13].

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 and Michele Filippone, 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).

[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 (2022).

[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, Nature Nanotechnology 17 (2022).

[6] Strong coupling between a photon and a hole spin in silicon, C. X. Yu, S. Zihlmann, J.- C. Abadillo-Uriel, V. P. Michal, N. Rambal, H. Niebojewski, T. Bedecarrats, M. Vinet, E. Dumur, M. Filippone, B. Bertrand, S. De Franceschi, Y.-M. Niquet and R. Maurand, arXiv (2022).

[7] All-electrical manipulation of silicon spin qubits with tunable spin-valley mixing, L. Bourdet and Y.-M. Niquet,Physical Review B97, 155433 (2018).

[8] 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 Letters120, 137702 (2018).

[9] Electrical manipulation of semiconductor spin qubits within the g-matrix formalism, B. Venitucci, L. Bourdet, D. Pouzada and Y.-M. Niquet, Physical Review B98, 155319 (2018).

[10] 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 B103, 045305 (2021).

[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).

[13] Hole spin manipulation in inhomogeneous and non-separable electric fields, B. Martinez, J.-C. Abadillo-Uriel, E. A. Rodriguez-Mena and Y.-M. Niquet, arXiv (2022).

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

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