Patent ID: 7755821

Claim:
A method of photon logic gates using a single or multiple quantum switches whose nonlinear optical medium is comprised of three closely spaced ground states | 1 >, | 2 > and | 3 > such that the transition among the said ground states is dipole forbidden, and an excited state | 4 > and | 5 > such that two-photon transitions between said ground state | 1 > and said | 3 >, said | 2 > and said | 3 >, and said | 1 > and said | 2 > via said excited state | 4 > (and said excited state | 5 > if said | 5 > is real energy state) are allowed, said method comprising following steps: a) applying to said nonlinear optical medium a first laser beam as an input beam A through an optical waveguide or free space at a frequency of ω A corresponding to a first transition between said ground state | 1 > and said excited state | 4 >; b) applying a second laser beam C through an optical waveguide or free space at a frequency of ω C corresponding to a second transition between said ground state | 2 > and said excited state | 4 >; c) applying a third laser beam S through an optical waveguide or free space at a frequency of ω S corresponding to a third transition between said ground state | 3 > and said excited state | 4 >; d) applying a fourth laser beam R through an optical waveguide or free space at a frequency of ω R corresponding to a third transition between said ground state | 3 > and said excited state | 5 >; e) adjusting the intensities of said first laser beam A, said second laser beam C, said third laser beam S, and said fourth laser beam R to produce nondegenerate four-wave mixing signals Q 1 at a frequency ω Q1 , or Q 2 at a frequency ω Q2 corresponding to the two-photon coherence induction [Reρ 23 ] 2 or [Reρ 13 ] 2 , respectively; f) connecting said nondegenerate four-wave mixing signals Q 1 and Q 2 to optical waveguides physically separated; g) connecting two quantum switches in a way to share said S and combine each said Q 1 or Q 2 together, respectively, via optical waveguides or free space; h) connecting two quantum switches in a way to combine nondegenerate four-wave mixing signals Q 1 from one quantum switch and Q 2 from the other quantum switch; i) connecting said Q 1 or Q 2 of the first quantum switch to said S of the second quantum switch via an optical waveguide or free space; j) connecting each said Q 1 and Q 2 of the first quantum switch to each said S of the second and third quantum switch via an optical waveguide or free space.