Parametric Amplification of Vacuum Fluctuations in a Spinor Condensate

Parametric amplification of vacuum fluctuations is crucial in modern quantum optics, enabling the creation of squeezing and entanglement. We demonstrate the parametric amplification of vacuum fluctuations for matter waves using a spinor F = 2(87) Rb condensate. Interatomic interactions lead to correlated pair creation in the m(F) = +/- 1 states from an initial m(F) = 0 condensate, which acts as a vacuum for m(F) not equal 0. Although this pair creation from a pure mF 0 condensate is ideally triggered by vacuum fluctuations, unavoidable spurious initial m(F) = +/- 1 atoms induce a classical seed which may become the dominant triggering mechanism. We show that pair creation is insensitive to a classical seed for sufficiently large magnetic fields, demonstrating the dominant role of vacuum fluctuations. The presented system thus provides a direct path towards the generation of nonclassical states of matter.