Purification of squeezed vacuum pulse generated from a Sagnac loop fiber using linear optics and conditional homodyne detection

Purification of quadrature squeezed vacuum pulses at the wavelength of 1.5 μm generated from a Sagnac loop fiber interferometer is experimentally demonstrated using linear optics and conditional homodyne detection. The anti-squeezed quadrature variance degraded by guided acoustic wave Brillouin scattering in the fiber is significantly improved from 12.6 to 4dB after the post selection, while the squeezed quadrature variance of -0.7 dB slightly decreases to -0.3 dB due to the linear optical loss caused by a beam splitter. This result agrees well with the theory.