Light-Based Computer Could Leapfrog Traditional Electric Chip Designs

A computer that uses light rather than electricity to transmit and manipulate data could perform the same tasks faster and using less energy

By Matthew Sparkes

A new type of computer that uses light instead of electricity could perform calculations faster, using less energy and less space.

Computer chips are made up of millions or billions of logic gates. These tiny components perform the most basic operations, such as checking whether one bit of data matches another. It is by combining these gates in large numbers that tasks such as downloading a file, playing a video, or playing a computer game are handled.

Traditional chips work by transporting electrons, but Yi-Zhang at Aalto University, Finland, and his colleagues succeeded in creating optical logic gates that perform the same functions with light.

Optical computers were created before, but they involve complex hardware and are limited to certain applications. Zhang says these new gates can be constructed from a single layer of molybdenum disulfide crystals just 0.65 nanometers thick using existing manufacturing techniques and could be designed to perform tasks universal in a small package.

Since photons move faster than electrons in a circuit, this could speed up calculations, and since they also move without resistance, they could do the same job using less energy.

The team’s approach uses circularly polarized light. It involves a light wave that appears to rotate around its axis of motion, rotating clockwise or counter-clockwise. A traditional bit in a computer consists of a positive or negative electrical charge – represented by 0 or 1 – but in this new optical computer, bits are represented either by clockwise polarized light or by counter-clockwise polarized light.

In the optical computer, the logic gates are made of crystalline materials sensitive to the spin direction of these polarized light beams. Using optical filters and other components, these gates can be constructed to recreate traditional gates.

The team demonstrated working optical gates that recreate the traditional gates known as XNOR, NOR, AND, XOR, OR, and NAND, all of which perform different operations on data. The researchers also showed that these operations can be performed on data in parallel rather than serially, which could potentially pave the way for great improvements in computational efficiency and speed.

“We hope that all-optical computers can be made in the future,” says Zhang. “The biggest advantage is the ultra-fast speed of optical chips compared to traditional chips. In addition, the light has the parallel processing ability and consumes less power, while electronic devices consume more power due to resistance.

Zhang says future work will investigate how optical logic gates could be used to create either hybrid classical and quantum computers or to create optical quantum logic gates. Indeed, a common branch of quantum computing research already uses photons to transmit data.

Journal reference: Scientists progressDOI: 10.1126/sciadv.abq8246