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Published April 8, 2022 | Version v1
Journal article Open

Optical control of the complex phase of a quantum ground state amplitude

  • 1. Department of Physics, Lund University, P.O. Box 118, SE-22100 Lund, Sweden
  • 2. Center for Complex Quantum Systems, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
  • 3. Center for Complex Quantum Systems, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark Aarhus Institute of Advanced Studies, Aarhus University, Hegh-Guldbergs Gade 6B, DK-8000 Aarhus C, Denmark

Description

We discuss how coherent driving of a two-level quantum system can be used to induce a complex
phase on the ground state and we discuss its geometric and dynamic contributions. While the global
phase of a wave function has no physical signi cance, coherent dynamics in a two-level subspace
provides relative phases and is an essential building block for more advanced dynamics in larger
systems. In this regard, we note that one must be careful with intuitive accounts of the phase
dynamics as it depends on the interaction picture applied. To mitigate ambiguities in practical
analyses, we suggest to complement the Bloch sphere picture with the path taken by the ground
state amplitude in the complex plane, and we show how the two-level pure state dynamics can serve
as a starting point for the study of the dynamics explored in three-level lambda systems, four level
tripod systems, and open quantum systems.

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Additional details

Funding

SQUARE – Scalable Rare Earth Ion Quantum Computing Nodes 820391
European Commission
AIAS-COFUND II – AIAS-COFUND II Fellowship Programme 754513
European Commission