Classical-Nonclassical Polarity of Gaussian States

Area of Science:

• Quantum Information Science
• Quantum Optics
• Quantum State Characterization

Background:

• Gaussian states are vital resources for quantum information processing, exhibiting nonclassical properties like squeezing and entanglement.
• Quantifying these properties in multimode Gaussian states presents significant challenges.

Purpose of the Study:

• To introduce a unified quantification method for nonclassical properties in Gaussian states.
• To establish a new metric, the classical-nonclassical polarity (P), for analyzing quantum states.

Main Methods:

• Development of the classical-nonclassical polarity (P) as a unified quantifier.
• Analysis of P for single-mode and multimode Gaussian states.
• Investigation of P's conservation under linear optical transformations.

Main Results:

• For single-mode states, P quantifies deviations from vacuum noise, indicating squeezing or classical mixtures.
• For multimode states, a positive P signifies bipartite quantum entanglement.
• The total classical-nonclassical polarity is conserved under linear optical transformations for two- and three-mode Gaussian states.
• For pure multimode Gaussian states, total polarity equals the sum of squeezing-related photon numbers.

Conclusions:

• The classical-nonclassical polarity offers a unified approach to quantifying nonclassicality and entanglement in Gaussian states.
• This work provides insights into the relationship between single-mode nonclassicality and entanglement.
• The findings may contribute to a unified resource theory for nonclassical features in quantum systems.