January 28, 2023

Observation of geometric phase in a molecular Aharonov-Bohm system using IBM Quantum Computer

The evolution of a quantum system is governed by the associated Hamiltonian. A system defined by a parameter-dependent Hamiltonian acquires a geometric phase when adiabatically evolved. Such an adiabatic evolution of a system having non-degenerate quantum states gives the well-studied Berry phase.

Lounguet-Higgins and co-workers discovered a geometric phase when considering the Jahn-Teller distortion described by the nuclear coordinates traversing a closed path about the point of intersection of the electronic potential energy surfaces. Under such a condition, the Born-Oppenheimer wave function undergoes a sign change corresponding to an introduced global phase of π radian. This change further introduces a multiple valuedness in the wavefunction which may be removed by adding a vector potential like term in the Hamiltonian for the nuclear motion giving the Molecular Aharonov Bohm effect.

The researcher team demonstrates a scheme to evaluate the introduced global phase for the molecular system considered by Longuet-Higgins and proposes methods as the first principle to do the same in more complex examples for the molecular Hamiltonian on a quantum computer. (Quantum Physics)

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