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Researchers build all-optical transistor; device could lead to new quantum computer design

Optical computing, or the use of light instead of electricity to complete calculations, is the most significant difference between traditional and quantum computers. Using optical computing, computers can make calculations much faster than traditional computers. Optical computing, as suggested by the name, requires light particles, or photons, to function. When two photons encounter one another, however, they tend to just pass through each other, making this technology difficult to achieve, Headlines & Global News explains.

A research team consisting of scientists from Massachusetts Institute of Technology (MIT) Research Laboratory of Electronics, Vienna University of Technology, and Harvard University came together to investigate how to manipulate the behavior of photons in order to create a successful optical computer server.

The team was able to create an optical switch using only one photon, referred to as a transistor’s optical analog. Quantum physics is more visible in individual particles, which is why it was possible to utilize only one photon to create the switch. In the switch are a pair of small, highly reflective mirrors. An optical beam of light passes through the mirrors when the switch is flipped. The two mirrors together act as an optical resonator, becoming transparent to light at the proper distance apart. When the switch is flipped off, only about 20 percent of the light can pass through.

When tiny particles of matter are in mutually exclusive states simultaneously, it is called superposition. Primitive quantum computers have struggled to keep ions in superposition. By using the optical switch, scientists are able to create arrays of optical circuits which are all held in superposition. Superposition is easier  to preserve in photons, making them the ideal candidate for use in quantum computing once the scientific team had discovered how to force them to interact.

A photon-switched transistor could also filter quantum noise by feeding the output back into the loop, something previously unseen. It could also be used as a photon detector, identifying a photon without destroying it. Previously, this was also impossible. The ability to detect photons without destroying them is key to utilizing the photons in quantum information processing, a press release from MIT explains.

The results of the study could be used to create computing chips with a longer-lasting battery and faster processing speeds. Jelena Vuckovic, a professor of electrical engineering at Stanford University, believes that it would be possible to reproduce the results of the study in physical systems that are easier to integrate into computer chips.