Optimal control of complex atomic quantum systems

• Published in: Scientific reports Vol. 6; no. 1; p. 34187
• Main Authors: van Frank, S, Bonneau, M, Schmiedmayer, J, Hild, S, Gross, C, Cheneau, M, Bloch, I, Pichler, T, Negretti, A, Calarco, T, Montangero, S
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 11.10.2016
• Subjects: Control theory; Phase transitions; Temperature effects
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep34187

Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control has been achieved on systems of increasing complexity. However, this control is still sub-optimal. In many scenarios, achieving a fast transformation is crucial to fight against decoherence and imperfection effects. Optimal control theory is believed to be the ideal candidate to bridge the gap between early stage proof-of-principle demonstrations and experimental protocols suitable for practical applications. Indeed, it can engineer protocols at the quantum speed limit - the fastest achievable timescale of the transformation. Here, we demonstrate such potential by computing theoretically and verifying experimentally the optimal transformations in two very different interacting systems: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We also show that such processes are robust with respect to perturbations, including temperature and atom number fluctuations.