Prospects for Octopus Rhodopsin Utilization in Optical and Quantum Computation

Visual membranes of octopus, whose main component is the light-sensitive signal transducer octopus rhodopsin (octR), are extremely highly ordered, easily capture single photons, and are sensitive to light polarization, which shows their high potential for use as a QC detector. However, artiˇcial membranes made of octR are neither highly enough ordered nor stable, while the bacterial homolog of octR, bacteriorhodopsin (bR), having the same topology as octR, forms both stable and ordered artiˇcial membranes but lacks the optical properties important for optical QC. In this study, we investigate the structural basis for ordering of the two proteins in membranes in terms of crystallization behavior. We compare atomic resolution 3D structures of octR and bR and show the possibility for structural bR/octR interconversion by mutagenesis. We also show that the use of (nano)biotechnology can allow (1) high-precision manipulation of the light acceptor, retinal, including converting its surrounding into that of bacterial rhodopsin, the protein already used in optical-computation devices and (2) development of multicomponent and highly regular 2D structures with a high potential for being efˇcient optical QC detectors.