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, under realistic experimental conditions, the Gaussian steering of two laser modes, A$\mathcal {A}$ and B$\mathcal {B}$, generated within the cascade transitions, respectively are examined. It is found that the scriptA→scriptB$\mathcal {A}\rightarrow \mathcal {B}$ steerability is always higher than that from scriptB→scriptA$\mathcal {B}\rightarrow \mathcal {A}$; in addition, the steering asymmetry cannot exceed ln 2, which implies that the state trueϱ̂scriptAB$\hat{\varrho }_{\mathcal {AB}}$ never diverges to an extremal asymmetry state. It is shown how squeezed noise can play a constructive role in realizing one‐way steering. As the main result, it is demonstrated that the state trueϱ̂scriptAB$\hat{\varrho }_{\mathcal {AB}}$ can exhibit one‐way steering solely from scriptA→scriptB$\mathcal {A}\rightarrow \mathcal {B}$, which is shown to emerge as a consequence of the fact that the intensity difference of the modes A$\mathcal {A}$ and B$\mathcal {B}$ is verified to remain always positive, irrespective of the physical and environmental parameters of trueϱ̂scriptAB$\hat{\varrho }_{\mathcal {AB}}$. The generated unidirectional one‐way steering may provide a useful resource for the distribution of the trust in future asymmetric quantum information tasks.