Observation of nonclassical correlations in biphotons generated from an ensemble of pure two-level atoms

Abstract

We report the experimental verification of nonclassical correlations for a four-wave-mixing process in an ensemble of cold two-level atoms, confirming theoretical predictions by Du et al. in 2007 for the violation of a Cauchy-Schwarz inequality in the system, and obtaining $R=(1.98\pm 0.03)\nleqq 1$. Quantum correlations are observed in a nano-seconds timescale, in the interference between the central exciting frequency and sidebands dislocated by the detuning to the atomic resonance. They prevail without filters over the noise background coming from linear scattering from the same optical transition. These correlations are fragile with respect to processes that disturb the phase of the atomic excitation, but are robust to variations in number of atoms and to increasing light intensities.

arXiv comment8 pages, 6 figures

References in corpus (18)

• Long-distance quantum communication with atomic ensembles and linear optics
• Generation of Nonclassical Photon Pairs for Scalable Quantum Communication with Atomic Ensembles
• Measurement-Induced Entanglement for Excitation Stored in Remote Atomic Ensembles
• Strong relative intensity squeezing by 4-wave mixing in Rb vapor
• Functional Quantum Nodes for Entanglement Distribution over Scalable Quantum Networks
• A millisecond quantum memory for scalable quantum networks
• Superradiance in a Large and Dilute Cloud of Cold Atoms in the Linear-Optics Regime
• Entanglement of a photon and a collective atomic excitation
• Experimental Vacuum Squeezing in Rubidium Vapor via Self-Rotation
• Efficient retrieval of a single excitation stored in an atomic ensemble
• Control of decoherence in the generation of photon pairs from atomic ensembles
• Squeezing with cold atoms
• Single-Photon Superradiance in Cold Atoms
• Controlled rephasing of single collective spin excitations in a cold atomic quantum memory
• Diffusing-Wave Spectroscopy of Cold Atoms in Ballistic Motion
• Experimental Fock-State Superradiance
• Two-Photon Beatings Using Biphotons Generated from a Two-Level System
• Nonvolatile optical memory via recoil-induced resonance in a pure two-level system

Cited by in corpus (1)

• Enhancing non-classical correlations for light scattered by an ensemble of cold two-level atoms