Time refraction and the quantum properties of vacuum (8 pages)

Jürgen Kästel, Michael Fleischhauer, Susanne F. Yelin +1 more

We discuss the feasibility of negative refraction with reduced absorption in coherently driven atomic media. Coherent coupling of an electric and a magnetic dipole transition by laser fields induces magnetoelectric cross coupling and negative refraction at dipole densities which are considerably smaller than necessary to achieve a negative permeability. At the same time the absorption gets minimized due to destructive quantum interference and the ratio of negative refraction index to absorption becomes orders of magnitude larger than in systems without coherent cross coupling. The proposed scheme allows for a fine tuning of the refractive index. We derive a generalized expression for the impedance of a medium with magnetoelectric cross coupling and show that impedance matching to vacuum can easily be achieved. Finally we discuss the tensorial properties of the medium response and derive expressions for the dependence of the refractive index on the propagation direction.

Peter W. Milonni

Carl Friedrich von Weizsäcker, Thomas Görnitz, Holger Lyre

Aida M. Awad, M.S. Badr, A.A. El-Rahman

The gain, absorption and dispersion properties of a probe field for a four level N-type atomic system with a normal vacuum and a squeezed vacuum fields is studied. Under such conditions that normal and squeezed vacuum-induced interference among decay channels is significant. Our study also reveals that the quantum interference will produce a remarkable effect on the absorption and dispersion properties of the system. A single squeezed vacuum is coupled to three transitions. Numerically the effect of the squeezing vacuum field parameters and the relative phases between the squeezed vacuum and the probe (strong) fields on the index of refraction is analyzed.

Edward B. Manoukian

Daniel L. Nedel

In this work new interaction terms between two SYK models are proposed, which allow to define an interaction picture such that it is possible to calculate the vacuum time dependent entanglement entropy at the conformal and large N limit. It is shown that the vacuum evolves as a time dependent SU(2) squeezed state and the time dependent entanglement entropy has the same form of the Page curve of Black Hole formation and evaporation.