| Quantum interference of twin optical beams, a typical example of correlated boson fields, is of great interest from the viewpoint of both fundamental and applied physics. Intensity correlated optical beams and their quantum interference bring the possibility of performing sub-shot-noise interferometry experiments which yield high-sensitivity in practical applications.; A type-II doubly resonant optical parametric oscillator (OPO) has been built for research in quantum optics, to provide a source of ultrastable quantum correlated (twin) optical beams with continuously tunable frequency difference from zero up to several THz. Three servo loops have been built to control the frequency difference of the twin optical beams and sub-hertz stability has been achieved for frequency difference up to 100MHz. In particular, frequency degenerate twin beams are indistinguishable macroscopic quantum systems.; A series of experimental results has been produced with these OPO-generated ultrastable twin beams: the observation of the generalized Hong-Ou-Mandel interference of untrastable twin optical beams, sub-shot-noise homodyne interferometry, and sub-shot-noise heterodyne polarimetry. |
