Complete population inversion of Bose particles by an adiabatic cycle

TL;DR

This paper demonstrates that an adiabatic cycle involving a delta-shaped potential can fully invert the population of Bose particles in a one-dimensional box, exciting all bosons from the ground to the first excited state.

Contribution

It introduces a novel adiabatic cycle method to achieve complete population inversion of Bose particles in a confined system.

Findings

All bosons are excited to the first excited state after the cycle.

The energy absorbed scales with the number of bosons.

The process creates a nonequilibrium state from an initial equilibrium.

Abstract

We show that an adiabatic cycle excites Bose particles confined in a one-dimensional box. During the adiabatic cycle, a wall described by a $\delta$-shaped potential is applied and its strength and position are slowly varied. When the system is initially prepared in the ground state, namely, in the zero-temperature equilibrium state, the adiabatic cycle brings all bosons into the first excited one-particle state, leaving the system in a nonequilibrium state. The absorbed energy during the cycle is proportional to the number of bosons.