TRFWM application for quantum computing

TL;DR: In this paper, it was shown that one can elaborate existing nonlinear optical technology in application to the one-way quantum computer scheme, which can be used in optical memory, as well as data processing and storage devices.

Abstract: Physical mechanism of the time resolved four-wave mixing (TRFWM) has been investigated for further implication in optical information processing. It was found that photon echo physical and optical characteristics allow to use it for parallel optical data processing. We show that one can elaborate existing nonlinear optical technology in application to the one-way quantum computer scheme. Time resolved four-wave mixing is widely known nonlinear optical effect. Photon echo (PE) is a particular case of TRFWM which is the most interesting for practical use. PE is a nonlinear optical effect, which allows time reversal in a system of atomic particles, including atoms, impurity in crystals, gas, or liquid molecules, etc. The photon echo is a result of interaction of ultrashort light pulses with matter – gases, condensed media, and plasmas. Due to its unique properties PE can be used in optical memory, as well as data-processing and storage devices. Three-pulse photon echo is the most suitable form of PE for use in various applications. Fig.1. Three-pulses photon echo. Three-pulse photon echo is the most suitable for practical applications. Suppose that a sample is irradiated with a sequence of three pulses. This leads to the emission of an optical coherent signal—a two-pulse photon echo at the moment t = 2τ and a three-pulse photon echo at the moment t = T + 2τ , where T is the time interval between the second and third pulses. The three-pulse photon-echo signal arises after the third pulse with a time delay equal to the interval τ between the first and the second pulses. The decay of the three-pulse echo signal is often independent of the position of the third pump pulse on the time scale.(fig.1) Optical echo processors [1]could be build on base of crystals doped with rare-earth ions, such as LaF3:Pr, CaWO4:Nd, YAlO3:Er, Gd2SiO5: Pr, Lu2SiO5:Pr,Y2SiO5:Pr possess a high optical damage threshold. It was shown that optical echo processor is currently capable of implementing all known methods of optical data processing, including the filtering of conventional (temporal and spatial) frequencies, as well as correlation comparison of optical signals and spatiotemporal images. The possibility of parallel processing of large data arrays, represented in the form of twoand three-dimensional optical images, and the flexibility in controlling data flows make a photon echo very attractive for the construction of digital systems. Architecture of a PE-based vector–matrix multiplier with a pixel structure is best suited for this purpose. Pixel structure is understood here as a medium, e.g., a Y2SiO5:Pr plate, with separate microdomains (pixels) inside this medium containing Pr impurity ions. These pixels are separated from each other and are arranged in a regular, crystal order. Pixel sizes lie within the mesoscopic range. Scheme of laser digital vector –matrix multiplier with a pixel structure consists of input and output linear arrays and in homogeneously broadened medium (e.g. LaF3:Pr) interacting with sequence of resonant optical pulses. Modification of basic optical processor scheme leads us to operation on two-dimensional data arrays. Minimization of the area containing single impurity ion leads us to the system with Ising-type coupling between neighboring impurity ions. Because of single impurity ion interaction quantum approach has been accepted. A scheme of quantum computation proposed by R. Raussendorf and J.Briegel in [2,3] consists of one-qubit measurements on a particular class of entangled states. In this model the entire resource QThC3-P4