# Transition probability generating function of a transitionless quantum parametric oscillator

## TL;DR

This paper derives a transition probability generating function for a transitionless quantum parametric oscillator using Husimi's method, linking classical and quantum dynamics to analyze the effects of counterdiabatic driving.

## Contribution

It introduces a novel method to explicitly calculate the transition probability generating function for a transitionless quantum parametric oscillator using classical solutions.

## Key findings

- Explicit solutions of the classical parametric oscillator are obtained.
- The time-dependent parameter reduces to the frequency ratio between Hamiltonians.
- Classical phase space trajectories illustrate the counterdiabatic Hamiltonian's effect.

## Abstract

The transitionless tracking (TT) algorithm enables the exact tracking of quantum adiabatic dynamics in an arbitrary short time by adding a counterdiabatic Hamiltonian to the original adiabatic Hamiltonian. By applying Husimi's method originally developed for a quantum parametric oscillator (QPO) to the transitionless QPO achieved using the TT algorithm, we obtain the transition probability generating function with a time-dependent parameter constituted with solutions of the corresponding classical parametric oscillator (CPO). By obtaining the explicit solutions of this CPO using the phase-amplitude method, we find that the time-dependent parameter can be reduced to the frequency ratio between the Hamiltonians without and with the counterdiabatic Hamiltonian, from which we can easily characterize the result achieved by the TT algorithm. We illustrate our theory by showing the trajectories of the CPO on the classical phase space, which elucidate the effect of the counterdiabatic Hamiltonian of the QPO.