Design of High Quality Chemical XOR Gates with Noise Reduction

Abstract

We describe a chemical XOR gate design that realizes gate‐response function with filtering properties. Such gate‐response function is flat (has small gradients) at and in the vicinity of all the four binary‐input logic points, resulting in analog noise suppression. The gate functioning involves cross‐reaction of the inputs represented by pairs of chemicals to produce a practically zero output when both are present and nearly equal. This cross‐reaction processing step is also designed to result in filtering at low output intensities by canceling out the inputs if one of the latter has low intensity compared with the other. The remaining inputs, which were not reacted away, are processed to produce the output XOR signal by chemical steps that result in filtering at large output signal intensities. We analyze the tradeoff resulting from filtering, which involves loss of signal intensity. We also discuss practical aspects of realizations of such XOR gates.

Experimental Realization of a High‐Quality Biochemical XOR Gate

“…Then additional reactants indicated in the scheme are added, and 15 min later the system's response is measured as the change in the intensity of absorbance of ABTS ox at the maximum at λ =415 nm. B) The corresponding simplified reaction scheme for effective processes considered in modelling . The biocatalytic reactions used in the XOR gate realization are explained in the text.…”

“…As described in the Introduction, it is difficult to design an XOR gate based on a simple chemical or biocatalytic reaction. Here we use the approach to have each of the two logic‐variable inputs to the XOR gate function as a combination of two chemicals, one of which reacts with a counterpart from the other input pair, whereas the remaining two (out of the four input reactants) are converted to the output . The reactions required for the present realization of such a gate are catalyzed by enzymes, with all the chemicals being substrates for enzymes, as shown in Figure A.…”

“…The reactions required for the present realization of such a gate are catalyzed by enzymes, with all the chemicals being substrates for enzymes, as shown in Figure A. Some of the chemicals shown in Figure A are not input or output “signals” but are introduced into the system as the XOR “gate machinery” (meaning non‐input/output chemical components always applied at the same initial concentration). The latter can be the required reactants, such as oxygen (marked as C and D , because it is an input for two biocatalytic processes, here assumed constant‐concentration, replenished from the outside during the process) or ABTS ( F , which is a function of time), and biocatalysts, etc., see Figure A.…”

“…Preliminary theoretical studies indicate that for high‐quality XOR of the type considered here, the initial values of the inputs should be related as follows. Input A (0) from 0 to A max , whereas its counterpart, A′ (0), should vary proportionately, but with a small additional incremental amount Δ A , see Equation : …”

The solvent effect on a styryl‐bodipy derivative functioning as an AND molecular logic gate

“…Such changes can be related to the operation of fluorescence chemosensors, molecular switches, and logic gates (via the familiar Boolean logic where the modulators correspond to the inputs and the observed changes correspond to the outputs) . As a consequence, the field of molecular logic gates and generally of chemosensors and molecular switches is very active and many research groups around the world work on these subjects …”