Patent ID: 6628453
Filing Date: 2003-09-30
Classification: G02F

Abstract:
A method of quantum switching using a nonlinear optical medium composing three closely spaced ground states |a>, |b> and |c> such that the transition among the ground states is dipole forbidden, and an excited state |d> such that the two-photon transitions between the ground state |a> and the |c>, the |b> and the |c>, and the |a> and the |b> via the excited state |d> are allowed, the method comprising following steps:a) applying a first laser beam to the nonlinear optical medium as an input beam through an optical fiber, waveguide, or free space at a frequency of &ohgr;1 corresponding to a first transition between the ground state |a> and the excited state |d>; b) applying a second laser beam to the nonlinear optical medium through an optical fiber, waveguide, or free space at a frequency of &ohgr;2 corresponding to a second transition between the ground state |b> and the excited state |d>; c) applying a third laser beam to the nonlinear optical medium through an optical fiber, waveguide, or free space at a frequency of &ohgr;3 corresponding to a third transition between the ground state |c> and the excited state |d>; d) adjusting the intensities of the first laser beam &ohgr;1, the second laser beam &ohgr;2, and the third laser beam &ohgr;3 to produce a strongly driven superposition state composed of the ground state |a> and the |c> creating two-photon coherence induction Repac; e) adjusting the frequency of the first laser beam &ohgr;1 to produce a strongly driven superposition state composed of the ground state |b> and the |c> creating two-photon coherence induction Repbc, whereas making the two-photon coherence induction Repac suppressed; f) applying a fourth laser beam &ohgr;p through an optical fiber or a free space corresponding to a fourth transition between the ground state |c> and the excited state |d> for nondegenerate four-wave mixing or phase conjugation geometry with either the first laser beam &ohgr;1 the &ohgr;3, and the &ohgr;p to produce nondegenerate four-wave mixing signal &ohgr;1d, or the second laser beam &ohgr;2, the &ohgr;3, and the &ohgr;p to produce nondegenerate four-wave mixing signal &ohgr;2d; and g) connecting the nondegenerate four-wave mixing signals &ohgr;1d and the &ohgr;2d to optical fibers physically separated.