title: Observation of two output light pulses from a partial wavelength converter preserving phase of an input light at a single-photon level.
abstract: We experimentally demonstrate that both of the two output light pulses of different wavelengths from a wavelength converter with various branching ratios preserve phase information of an input light at a single-photon level. In our experiment, we converted temporally-separated two coherent light pulses with average photon numbers of ∼ 0.1 at 780 nm to light pulses at 1522 nm by using difference-frequency generation in a periodically-poled lithium niobate waveguide. We observed an interference between temporally-separated two modes for both the converted and the unconverted light pulses at various values of the conversion efficiency. We observed interference visibilities greater than 0.88 without suppressing the background noises for any value of the conversion efficiency the wavelength converter achieves. At a conversion efficiency of ∼ 0.5, the observed visibilities are 0.98 for the unconverted light and 0.99 for the converted light. Such a phase-preserving wavelength converter with high visibilities will be useful for manipulating quantum states encoded in the frequency degrees of freedom.
authors: Rikizo
authors: R
authors: Ikuta
authors: Toshiki
authors: T
authors: Kobayashi
authors: Hiroshi
authors: H
authors: Kato
authors: Shigehito
authors: S
authors: Miki
authors: Taro
authors: T
authors: Yamashita
authors: Hirotaka
authors: H
authors: Terai
authors: Mikio
authors: M
authors: Fujiwara
authors: Takashi
authors: T
authors: Yamamoto
authors: Masahide
authors: M
authors: Sasaki
authors: Zhen
authors: Z
authors: Wang
authors: Masato
authors: M
authors: Koashi
authors: Nobuyuki
authors: N
authors: Imoto