Achieving ground state and enhancing entanglement by recovering information

TL;DR

This paper demonstrates that by recovering information lost due to finite cavity bandwidth in optomechanical systems, one can surpass the traditional resolved-sideband limit to achieve ground state cooling and significantly enhance entanglement.

Contribution

It introduces a feedback control method to recover information lost in cavity bandwidth, enabling surpassing the resolved-sideband limit and improving optomechanical entanglement.

Findings

Surpassing the resolved-sideband limit with feedback control.

Enhanced entanglement at high environmental temperatures.

Information recovery acts as a quantum eraser.

Abstract

For cavity-assisted optomechanical cooling experiments, it has been shown in the literature that the cavity bandwidth needs to be smaller than the mechanical frequency in order to achieve the quantum ground state of the mechanical oscillator, which is the so-called resolved-sideband or good-cavity limit. We provide a new but physically equivalent insight into the origin of such a limit: that is information loss due to a finite cavity bandwidth. With an optimal feedback control to recover those information, we can surpass the resolved-sideband limit and achieve the quantum ground state. Interestingly, recovering those information can also significantly enhance the optomechanical entanglement. Especially when the environmental temperature is high, the entanglement will either exist or vanish critically depending on whether information is recovered or not, which is a vivid example of a quantum eraser.