Quantum transition probabilities due to overlapping electromagnetic pulses: Persistent differences between Dirac's...

Area of Science:

• Quantum mechanics
• Quantum optics

Background:

• Two methods for calculating transition probabilities in time-dependent electromagnetic fields exist: Dirac's standard method and Landau-Lifshitz's nonadiabatic approach.
• Previous work showed these methods differ during field application.
• Landau-Lifshitz considered only linear response and constant perturbations.

Purpose of the Study:

• To prove that differences between Dirac's and Landau-Lifshitz's methods can persist after the perturbing fields are removed.
• To investigate lasting differences in transition probabilities, including cases with dephasing.

Main Methods:

• Designed a system with two overlapping electromagnetic pulses (a "plateau" pulse and an infrared pulse).
• The "plateau" pulse populates an excited state and creates coherences.
• The infrared pulse acts after dephasing, while the first pulse's field is constant.

Main Results:

• Demonstrated that differences between the two transition probability calculation methods can persist post-perturbation.
• Observed lasting differences exceeding 35% when pulse frequencies are on resonance.
• Found larger differences for off-resonant perturbations.

Conclusions:

• The nonadiabatic perturbation theory allows for dephasing, which Dirac's method does not account for in the perturbed wave function.
• This study extends Landau-Lifshitz analysis by considering non-constant fields and the absence of residual perturbation.
• The findings highlight the importance of considering nonadiabatic effects and dephasing for accurate quantum system dynamics.