ELFT HÍRADÓ

[Szeminárium koordinátor <szfi-seminar AT wigner.mta.hu>]

SZFI SeminarAndrea AlbertiUniversitaet Bonn (host: Asbóth János)Controlling 
atomic wave packets at the quantum speed limitTuesday, 3 September 2019, 
10:00, KFKI Campus, Bldg. 1, 2nd floor, Conference RoomI will report on the 
experimental realization of fast, high-fidelity transport of atomic wave 
packets in deep optical lattices. The goal here is to transport atoms by one 
or more lattice sites in the shortest time allowed by quantum mechanics, 
under the constraint that no motional excitation is created after transport, 
and the optical lattice depth does not exceed a maximum value given by the 
available resources (e.g., finite laser power). To achieve fast atom 
transport, we use quantum optimal control, which allows several motional 
excitations to be created during the transport process, and yet refocus them 
back into the motional ground state with a fidelity at around 99%. Optimizing 
the process for various transport times, we clearly observe a minimum time 
below which transport operations unavoidably create motional excitations. 
This time defines the quantum speed limit for the transport operation. From 
the experimental data, we deduce that such a minimal transport time is 
essentially determined by the harmonic period of the trapping potential. 
Theoretically, such a time can be estimated using the energy uncertainty and 
the Fubini-Study metric quantifying the path length connecting the initial 
and final states. I will show that the fast atom transport in spin-dependent 
optical lattices allows us to outrun decoherence, and thus to improve 
coherence of Mach-Zehnder atom interferometers and of quantum-walk 
experiments, where atoms are delocalized in space through a multiplicity of 
quantum paths. Finally, I will conclude with an outlook towards 
two-dimensional quantum-walk experiments for the study of anomalous Floquet 
Chern topological insulators using pseudo spin-1/2 particles [1].[1] Sajid et 
al., “Creating anomalous Floquet Chern insulators with magnetic quantum 
walks” Phys. Rev. B 99, 214303 (2019). Minden érdeklődőt szívesen 
látunk! - Everyone is welcome to attend.Róbert 
Juhászszfi-seminar AT wigner.mta.hu