January 24 2019

24 till 25.01.2019: Visit of Prof. Ennio Arimondo (Università di Pisa and INO-CNR)

Prof. Ennio Arimondo (Università di Pisa and INO-CNR) will visit us from Thursday 24.01.2019 to Friday 25.01.2019 .

He will give a talk in the physics colloquium on Thursday 24.01.2019 at 16:15 in building C6 4 lecture hall II.

Superadiabatic control of quantum systems

Quantum control and quantum computation, relying on the engineering of ad-hoc Hamiltonians, explore the evolution of quantum systems towards precisely defined targets. A basic task is the preparation of the system in a given quantum eigenstate. In particular an important goal is to keep a quantum system in the lowest energy state. This task is typically realized by a very slow adiabatic modification of the control Hamiltonian. Within the last few years a large theoretical and experimental effort has developed superadiabatic quantum protocols providing perfect and very fast quantum control. This control of quantum processes was developed in different areas from atomic physics, to solid-state physics and molecular physics. The "simplest non-simple quantum problem" is the evolution of a two- level quantum system with a time-dependent Hamiltonian. A paradigmatic example of such a system is the Landau-Zener (LZ) problem, in which two levels whose energy depends on time experience an avoided crossing. If the time variation of the energy levels is linear, the resulting evolution gives rise to the well-known expression for the LZ tunneling. For this problem the goal of perfect preparation of the final state can only be achieved for infinitely slow sweep speeds or for infinitely large coupling strengths, both of which are impractical. The speeded-up superadiabatic approach is to use shortcuts to adiabaticity protocols, which may be defined broadly as the processes leading to the same final target state in a shorter time. These protocols for a given time-varying Hamiltonian construct an auxiliary Hamiltonian that cancels the non-adiabatic part of the original Hamiltonian and thus ensures the targeted quantum evolution. Similar schemes have been proposed for systems with three or more levels. A large variety of alternative protocols have been proposed in order to obtain similar efficient and fast transfers. The presentation is focused on the basic of the superadiabatic approach, and on few experimental results obtained at Pisa and elsewhere..

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