Variational study of a two-level system coupled to a harmonic oscillator in a ultrastrong coupling regime

Understand

The nonclassical behaviors of a two-level system coupled to a harmonic oscillator is investigated in the ultrastrong coupling regime.

• We revisit the variational solution of the ground state and find that the existing solution do not account accurately for nonclassical effects such squeezing.
• We suggest a new trial wave function and demonstrate that it has an excellent accuracy on the quantum correlation effects as well as on energy.