Quantum Non-Gaussianity Criterion Based on Photon Correlations g^{(2)} and g^{(3)}.

Area of Science:

• Quantum optics
• Quantum information science

Background:

• Quantum non-Gaussian states are essential for achieving quantum advantage in continuous variable systems.
• These states are a benchmark for advanced quantum light sources and cannot be produced by simple methods like displacement and squeezing.

Purpose of the Study:

• To introduce a novel, attenuation-resistant criterion for identifying quantum non-Gaussian states.
• To experimentally validate this criterion using a quantum dot single-photon source.

Main Methods:

• Utilizing second- and third-order correlation functions (g⁽²⁾ and g⁽³⁾) to establish a nonlinear bound.
• The criterion is defined by the inequality: sqrt[g⁽³⁾] + 3sqrt[g⁽²⁾] ≥ 2 for classical mixtures of Gaussian states.

Main Results:

• A violation of the established inequality confirms quantum non-Gaussianity.
• Experimental results from a quantum dot single-photon source yielded sqrt[g⁽³⁾] + 3sqrt[g⁽²⁾] = 0.174(13).
• This result demonstrates quantum non-Gaussianity with a statistical significance exceeding 100 standard deviations.

Conclusions:

• The developed criterion provides a robust method for detecting quantum non-Gaussian states.
• Experimental verification confirms the criterion's effectiveness and the non-Gaussian nature of the quantum dot source.