Entanglement Limits in Hybrid Spin-Mechanical Systems

TL;DR

This paper explores the limits of entanglement in hybrid spin-mechanical systems, analyzing how input squeezing, coupling strengths, and resonance conditions affect entanglement generation and robustness.

Contribution

It provides a detailed analysis of entanglement dynamics in spin-optomechanical systems, highlighting the effects of various parameters on entanglement saturation and transfer.

Findings

Spin cavity entanglement saturates regardless of input squeezing.

Mechanical interaction reduces spin-cavity entanglement.

Maximum entanglement occurs when cavity and spin resonance conditions match.

Abstract

We investigate how to generate continuous-variable entanglement between distant optomechanical and spin systems, by transferring input two-mode squeezed vacuum state to the system. Such a setup has been proposed for backaction evading gravitational-wave measurement, squeezing the output noise below the standard quantum limit. We find that the spin cavity entanglement saturates to a particular value when no mechanics are involved even though the entanglement of the input beam increases steadily, and drops down when the mechanical oscillator interacts with the cavity. Our study also reveals that the spin optical readout rate enables the robustness of the spin-cavity entanglement with input squeezing whereas the optomechanical coupling strength disables it. The entanglement reaches its maximum when the effective resonance frequency and bandwidth of the cavity match the spin system. Determining collective quadrature fluctuations, our analysis also shows that even though the entanglement between spin and cavity, and cavity and mechanics is significantly present; it is still impossible to obtain entanglement between spin and mechanical oscillator.