Continuous sampling of the squeezed state nonclassicality

Abstract

We report the direct -- continuous in phase -- sampling of a regularized $P$ function, the so-called nonclassicality quasiprobability, for squeezed light. Through their negativities, the resulting phase-space representation uncovers the quantum character of the state. In contrast to discrete phase-locked measurements, our approach allows an unconditional verification of nonclassicality by getting rid of interpolation errors due to fixed phases. To realize the equal phase distribution of measured quadratures, a data selection is implemented with quantum random numbers created by measuring the vacuum noise. The continuously measured squeezed field was generated in an optical parametric amplifier. Suitable pattern functions for obtaining the regularized $P$ function are investigated. The significance of detecting negativities in our application is determined. The sampling of nonclassicality quasiprobabilities is shown to be a powerful and universal method to visualize quantum effects within arbitrary quantum states.

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• Conditional Hybrid Nonclassicality
• Probing nonclassicality with matrices of phase-space distributions
• Time-dependent nonlinear Jaynes-Cummings dynamics of a trapped ion
• Anomalous Quantum Correlations of Squeezed Light
• Tracking quantum coherence in polariton condensates with time-resolved tomography
• Quantum correlations in composite systems
• Unbalanced Homodyne Correlation Measurements
• Quasistates and quasiprobabilities
• Uncertainty relations for characteristic functions
• Time-dependent quantum correlations in phase space
• Identifying nonclassicality from experimental data using artificial neural networks
• Gaussian versus non-Gaussian filtering of phase-insensitive nonclassicality
• Preparation of arbitrary quantum states with regular $P$~functions
• Quantum effects of operator time ordering in the nonlinear Jaynes-Cummings model
• Optomechanical state reconstruction and nonclassicality verification beyond the resolved-sideband regime
• Elementary test for non-classicality based on measurements of position and momentum
• Effect of relativistic motion on witnessing non-classicality of quantum states
• Filter functions for the Glauber-Sudarshan $P$-function regularization