Phase-dependent squeezing and entanglement in a cavity QED

Abstract

The output squeezed spectrum of the output two modes from a cavity QED system which is embedded by a four-level atom driven by two classical fields are calculated. The effects of the cavity decay rates, relative phase between two classical fields, and effective coupling constants between the atom and the cavity on the entanglement and squeezing of the two cavity modes are investigated. It is shown that the depth of the squeezing or entanglement spectrum is insensitive to the cavity decay rates while its width is dependent on the cavity decay rates and the coupling constants. In particular, the squeezing or entanglement spectrum including their maximal values and widths is remarkably affected by the relative phase between the classical fields. It is found that the output spectrum varies with the relative phase in a cosine-like behavior with a period of 2π. The results can indicate how to suitably adjust the relative phase for acquiring maximal squeezing or perfect entanglement for the two cavity fields. This will be useful in quantum communication and computation.