Unidirectional Gaussian One-Way Steering

Abstract

Steering is a type of quantum nonlocality that exhibits an inherent asymmetry between two observers. In a nondegenerate three-level laser coupled to a two-mode squeezed vacuum reservoir, we examine, under realistic experimental conditions, the Gaussian steering of two laser modes, $\mathcal{A}$ and $\mathcal{B}$, generated within the cascade transitions, respectively. We find that the $\mathcal{A}\rightarrow \mathcal{B}$ steerability is always higher than that from $\mathcal{B}\rightarrow \mathcal{A}$; in addition, the steering asymmetry cannot exceed $\ln 2$, which implies that the state $\hat{\varrho}_{\mathcal{AB}}$ never diverges to an extremal asymmetry state. We show how squeezed noise can play a constructive role in realizing one-way steering. As the main result, we demonstrate that the state $\hat{\varrho}_{\mathcal{AB}}$ can exhibit one-way steering solely from $\mathcal{A}\rightarrow \mathcal{B}$, which we show to emerge as a consequence of the fact that the intensity difference of the modes $\mathcal{A}$ and $\mathcal{B}$ is verified to remain always positive, irrespective of the physical and environmental parameters of $\hat{\varrho}_{\mathcal{AB}}$. The generated unidirectional one-way steering may provide a useful resource for the distribution of the trust in future asymmetric quantum information tasks.