Quantum driving of a two level system: quantum speed limit and superadiabatic protocols _ an experimental investigation

6th International Workshop DICE2012 Spacetime – Matter – Quantum Mechanics: From the Planck Scale to Emergent Phenomena

物理学;力学

Malossi, N.^1 ; Bason, M.G.^2,4 ; Viteau, M.^2,5 ; Arimondo, E.^1,2,3 ; Ciampini, D.^1,2,3 ; Mannella, R.^1 ; Morsch, O.^2

Università di Pisa, Dipartimento di Fisica 'E. Fermi, Lgo Pontecorvo 3, I-56127 Pisa, Italy^1

INO-CNR, Dipartimento di Fisica E. Fermi, Lgo Pontecorvo 3, I-56127 Pisa, Italy^2

CNISM UdR Pisa, Dipartimento di Fisica E. Fermi, Lgo Pontecorvo 3, I-56127 Pisa, Italy^3

Department of Physics and Astronomy, Aarhus University Aarhus, Denmark^4

Orsay Physics, 95 av. des Monts Aurliens, ZAC Saint Charles, 13710 Fuveau, France^5

关键词: Bose-Einstein condensates;    Degree of control;    Experimental investigations;    Experimental parameters;    Hamiltonian parameters;    High-fidelity controls;    Quantum-information processing;    Two-level system;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/442/1/012062/pdf
DOI  :  10.1088/1742-6596/442/1/012062

学科分类：力学，机械学

来源: IOP

【 摘 要 】

A fundamental requirement in quantum information processing and in many other areas of science is the capability of precisely controlling a quantum system by preparing a quantum state with the highest fidelity and/or in the fastest possible way. Here we present an experimental investigation of a two level system, characterized by a time-dependent Landau-Zener Hamiltonian, aiming to test general and optimal high-fidelity control protocols. The experiment is based on a Bose-Einstein condensate (BEC) loaded into an optical lattice, then accelerated, which provides a high degree of control over the experimental parameters. We implement generalized Landau-Zener sweeps, comparing them with the well-known linear Landau-Zener sweep. We drive the system from an initial state to a final state with fidelity close to unity in the shortest possible time (quantum brachistochrone), thus reaching the ultimate speed limit imposed by quantum mechanics. On the opposite extreme of the quantum control spectrum, the aim is not to minimize the total transition time but to maximize the adiabaticity during the time-evolution, the system being constrained to the adiabatic ground state at any time. We implement such transitionless superadiabatic protocols by an appropriate transformation of the Hamiltonian parameters. This transformation is general and independent of the physical system.