Volume 78, Number 4, May 2007
Article Number 40004
Number of page(s) 5
Section General
Published online 09 May 2007
EPL, 78 (2007) 40004
DOI: 10.1209/0295-5075/78/40004

Observation of twin beam correlations and quadrature entanglement by frequency doubling in a two-port resonator

O.-K. Lim, B. Boland and M. Saffman

Department of Physics, University of Wisconsin - 1150 University Avenue, Madison, WI 53706, USA

received 12 February 2007; accepted in final form 10 April 2007; published May 2007
published online 9 May 2007

We demonstrate production of short wavelength beams with nonclassical intensity correlations and quadrature entanglement using second harmonic generation in a nonlinear resonator with two output ports. The two output beams at the harmonic frequency have no direct interaction but are both nonlinearly coupled to a common pump beam. The nonlinear coupling produces amplitude and phase correlations between the beams which results in quadrature entanglement. The output beams at $\lambda =428.5\,{\rm nm}$ are shown to exhibit 0.6 dB of amplitude quadrature squeezing, 0.9 dB of nonclassical intensity correlations, and $0.3\,{\rm dB}$ of entanglement using about 30 mW of pump power.

03.67.Mn - Entanglement production, characterization and manipulation .
42.50.Dv - Nonclassical states of the electromagnetic field, including entangled photon states; quantum state engineering and measurements .
42.65.Ky - Frequency conversion; harmonic generation, including higher-order harmonic generation .

© Europhysics Letters Association 2007