Various approaches to realize optical computers

Various approaches to realize optical computers

An optical computer is a computer that performs calculations using light instead of conventional electrons. The advantage over conventional computers is that optical processing consumes far less power than electronic processing, which generates heat and consumes enormous amounts of power. Another advantage is that spatial parallel processing is possible, which can significantly increase processing speed.

On the other hand, it is difficult to build a large-scale logic circuit like that of electronic information, so a practical optical computer has not yet been realized.

One of the most famous examples of an optical computer in the world of science fiction is the optical computer technology of the Kryptonians, Superman’s home planet. In the scene where Superman builds a base in the solitude of the North Pole, the crystals multiply themselves to create a base based on this technology. These technologies are theoretically real. I will discuss the individual elemental technologies below.

First, let’s look at the memory function, which is simple and easy to imagine. It is called the “Superman Memory Crystal. Using a technique called laser etching, a research team at the University of Southampton in England has succeeded in storing the above document and Isaac Newton’s “Optics” on a glass disk the size of a coin. The glass disks can retain their condition for billions of years at temperatures of 190 degrees Celsius. At room temperature, it can retain the information virtually forever.

The first “5D data storage” was presented by Prof. Kazansky and his colleagues in 2013. This is done by using femtosecond lasers, which produce extremely short pulses of light, to imprint information onto nanostructured dots.

The nano-sized etchings polarize light as it passes through the glass. The name “five-dimensional” refers to the three dimensions of the nanostructure, as well as its size and orientation.

Next, let’s look at the computing function.” The technology is now available to realize an “optical computer” that uses photons instead of electrons! From “Advances in the Development of “Photon Devices”?

Photons have characteristics superior to electrons, such as being electrically neutral and directional, making them suitable as particles (or waves) for transmission in circuits. However, in order for photons to pass through a microscopic circuit, the interior of the circuit must reflect light like a mirror. Optical fibers have such properties, but the precision of circuits in today’s commercial computers has reached several nanometers, making it difficult to process optical fibers to such a fine level. Photonic crystals” are a technology that can control the way light travels on a nanometer scale.

Photonic crystals have the property of reflecting only specific wavelengths of light, and by creating spaces inside them, they can be processed into microscopic circuits that allow light to pass through. Until now, however, it has been difficult to create ideal photonic crystals with human scientific capabilities. According to a paper published in Nature on September 23, 2020, researchers at New York University have developed a self-assembling photonic crystal.

Photonic crystals are made by forming a diamond-shaped lattice structure of four basic units, or colloids, of plastic particles. Diamond-shaped lattice crystals have an excellent ability to reflect light, and by modifying the design of the constituent particles, it is possible to control the wavelength of the reflected light over a wide range. However, although existing technology can assemble plastic particles into pyramids, it has not yet shown how to assemble them into giant photonic crystals.

In contrast, the method presented in “Colloidal diamond,” as shown in the figure below, first agglomerates four plastic particles into a single drop of oil, then pushes the oil in the center to the surface, and finally attaches a single-stranded DNA to the surface of the extruded oil drop. The crystals grew autonomously over time, creating giant photonic crystals as shown in the figure below.

In the self-propagation scene of Superman’s crystal, solid crystals are grown in air, but a realistic solution would be to grow organic crystals in a liquid, as described above.

One of the oldest types of image information input, processing, and output is the Spatial Light Modulator (SLM). This is a device that changes (modulates) light by electrically controlling the spatial distribution (amplitude, phase, polarization, etc.) of light from a light source, and the irradiated light is modulated by an element such as a liquid crystal to freely control its wavefront shape.

By using these devices, for example, the “ultra-high definition spatial light modulation device” presented at NHK has developed a high-definition, high-speed display device that can also display stereoscopic images.

As described above, there are various ways to realize each elemental technology in principle in terms of hardware. The final hurdle is how to construct software that “self-propagates.

By using recurrent algorithms, it is easy to form fractal patterns as described in “The Internet and Vairochanabutsu: The Kegon Sutra and Esoteric Buddhism” and other works.

However, just because they are complex forms, they cannot have any meaning or intention. It is necessary to put some kind of meta-information structure on them, as described in “Concrete and Abstract – Semantics and Explanation of Natural Language” and “Ontology Technology“.

We will discuss these software approaches separately.