Production of entangled images by four-wave mixing

A study was conducted to demonstrate the production of entangled images by four-wave mixing (4WM) process. The study demonstrated that nondegenerate 4WM in a ⁸⁵Rb vapor cell can produce highly multispatial-mode quantum-correlated twin beams. The 4WM process was based on a double-lambda configuration in which a strong pump field was mixed with two weak fields, the probe, and the conjugate. It was also demonstrated that a single probe and a conjugate photon were generated for each pair of absorbed pump photons. It was observed that the 4WM technology was simple, requiring about 400 mW of pump light and a 12 mm long Rb cell at 110°C to produce more than 8 dB of intensity-difference squeezing. Beams of light entangled in the continuous variable regime displayed correlations between their phases and amplitudes. These variables were measured by homodyning each of the beams with a strong reference beam, called the local oscillator (LO).