QuSCo on-air: Dominique Sugny “Understanding the quantum world with a tennis racket: How classical mechanics helps control qubits”

Prof Dominique Sugny was our guest for the March 2021 QuSCo on-air session with his talk “Understanding the quantum world with a tennis racket: How classical mechanics helps control qubits”


The design of efficient and robust pulse sequences is a fundamental requirement in quantum control and quantum technologies. Numerical methods can be used for this purpose, but with relatively little insight into the control mechanism or into the fundamental limits of the pulse [1]. In this talk, we show that the rotation of a classical system plays a fundamental role in the control of two-level quantum systems, or qubits. In the first part, we focus on the tennis racket effect, a geometric phenomenon which occurs in the free rotation of a rigid body. We prove that a perfect twist of the racket is achieved in the limit of an ideal asymmetric object [2]. A similar approach describes the Dzhanibekov effect in which a wing nut, spinning around its central axis, suddenly makes a half-turn flip and the monster flip, an almost impossible skateboard trick. Using a mapping between the rotation of a rigid body and the dynamics of a qubit, we derive for the qubit a family of control fields from the tennis racket effect. This family depends on two free parameters, which allow us to adjust the efficiency, the time and the robustness of the control process [3]. A quantum analog of the tennis racket effect is proposed and experimental results illustrate this theoretical study. Finally, we discuss other applications of this classical effect in the rotation of asymmetric molecules [4].


[1]- Training Schrodinger’s cat: quantum optimal control

  1. J. Glaser et al.

Eur. Phys. J. D 69, 79 (2015)

[2]- Geometric origin of the Tennis Racket Effect

  1. Mardesic, G. J. Gutierrez Guillen, L. Van Damme and D. Sugny

Phys. Rev. Lett. 125, 064301 (2020)

[3]- The quantum tennis racket effect: Linking the rotation of a rigid body to the Schrodinger equation

  1. Van Damme, D. Leiner, P. Mardesic, S. J. Glaser and D. Sugny

Sci. Rep. 7, 3998 (2017)

[4]- Quantum control of molecular rotation

  1. P. Koch, M. Lemeshko and and D. Sugny

Rev. Mod. Phys. 91, 035005 (2019)


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