Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Researchers build an all-optical transistor: An optical switch that can be turned on by a single photon could point toward new designs for both classical and quantum computers

Graphic: Christine Daniloff/MIT
Graphic: Christine Daniloff/MIT

Abstract:
Optical computing — using light rather than electricity to perform calculations — could pay dividends for both conventional computers and quantum computers, largely hypothetical devices that could perform some types of computations exponentially faster than classical computers.

Researchers build an all-optical transistor: An optical switch that can be turned on by a single photon could point toward new designs for both classical and quantum computers

Cambridge, MA | Posted on July 5th, 2013

But optical computing requires light particles — photons — to modify each other's behavior, something they're naturally averse to doing: Two photons that collide in a vacuum simply pass through each other.

In the latest issue of the journal Science, researchers at MIT's Research Laboratory of Electronics — together with colleagues at Harvard University and the Vienna University of Technology — describe the experimental realization of an optical switch that's controlled by a single photon, allowing light to govern the transmission of light. As such, it's the optical analog of a transistor, the fundamental component of a computing circuit.

Moreover, since the weird, counterintuitive effects of quantum physics are easier to see in individual particles than in clusters of particles, the ability to use a single photon to flip the switch could make it useful for quantum computing.

The heart of the switch is a pair of highly reflective mirrors. When the switch is on, an optical signal — a beam of light — can pass through both mirrors. When the switch is off, only about 20 percent of the light in the signal can get through.

The paired mirrors constitute what's known as an optical resonator. "If you had just one mirror, all the light would come back," explains Vladan Vuletić, the Lester Wolfe Professor of Physics at MIT, who led the new work. "When you have two mirrors, something very strange happens."

Light can be thought of as particles — photons — but it can also be thought of as a wave — an electromagnetic field. Even though, on the particle description, photons are stopped by the first mirror, on the wave description, the electromagnetic field laps into the space between the mirrors. If the distance between the mirrors is precisely calibrated to the wavelength of the light, Vuletić explains, "Basically, a very large field builds up inside the cavity that cancels the field coming back and goes in the forward direction." In other words, the mirrors become transparent to light of the right wavelength.

Clouding over

In the RLE researchers' experiment, the cavity between the mirrors is filled with a gas of supercooled cesium atoms. Ordinarily, these atoms don't interfere with the light passing through the mirrors. But if a single "gate photon" is fired into their midst at a different angle, kicking just one electron of one atom into a higher energy state, it changes the physics of the cavity enough that light can no longer pass through it.

Joining Vuletić on the paper are lead author Wenlan Chen and Kristin M. Beck, both PhD students in his group; Robert Bücker of the Vienna University of Technology; and Michael Gullans, Mikhail D. Lukin and Haruka Tanji-Suzuki of Harvard.

For conventional computers, the chief advantage of optical computing would be in power management: As computer chips have more and more transistors crammed onto them, they draw more power and run hotter. Computing with light instead of electricity would address both problems.

Of course, clouds of supercooled atoms are not a practical design for the transistors in, say, a Web server. "For the classical implementation, this is more of a proof-of-principle experiment showing how it could be done," Vuletić says. "One could imagine implementing a similar device in solid state — for example, using impurity atoms inside an optical fiber or piece of solid."

Going quantum

Quantum-computing applications may be more compelling. Bizarrely, tiny particles of matter can be in mutually exclusive states simultaneously, something known as superposition. Where a bit in a classical computer can be either on or off, representing 0 or 1, bits built from particles in superposition can represent 0 and 1 at the same time. As a consequence, they could, in principle, evaluate many possible solutions to a computational problem in parallel, rather than considering them one by one.

Primitive quantum computers have been built using laser-trapped ions and nuclear magnetic resonance, but it's hard to keep their bits — or "qubits," for quantum bits — in superposition. Superposition is much easier to preserve in photons, for exactly the same reason that it's hard to get photons to interact.

The ability to switch an optical gate with a single photon opens the possibility of arrays of optical circuits, all of which are in superposition. "If the gate photon is there, the light gets reflected; if the gate photon is not there, the light gets transmitted," Vuletić explains. "So if you were to put in a superposition state of the photon being there and not being there, then you would end up with a macroscopic superposition state of the light being transmitted and reflected."

A photon-switched transistor has other implications for quantum computing. For instance, Vuletić says, one of the first applications of a conventional transistor was to filter noise out of an electrical signal by feeding the transistor's output back into it. "Quantum feedback can cancel — to the extent allowed by quantum mechanics — quantum noise," Vuletić says. "You can make quantum states that you wouldn't otherwise get."

The switch could also be used as a photon detector: If a photon has struck the atoms, light won't pass through the cavity. "That means you have a device that can detect a photon without destroying it," Vuletić says. "That doesn't exist today. It would have many applications in quantum information processing."

"Energy consumption in computing devices is a big issue," says Jelena Vuckovic, a professor of electrical engineering at Stanford University. "The beauty of this approach is that it can really do switching at the single-photon level, so your losses are much smaller. You don't have to spend a lot of energy for each bit. Your bit is essentially included in a single photon."

Vuckovic believes that it should be possible to reproduce the MIT researchers' results in physical systems that are easier to integrate into computer chips. "It's exactly the same story, except that instead of using these ultracold atoms in the cavity, you use a microscopic cavity on a semiconductor chip on a semiconductor and you use a quantum dot grown inside of the semiconductor as an artificial atom," she says. "There would be extra steps that people would have to take in order to implement the right energy-level structure. But in principle, the physics could be translated to a platform that could be cascaded and more easily integrated."

####

For more information, please click here

Copyright © Massachusetts Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Quantum twisted Loong confirms the physical reality of wavefunctions September 23rd, 2017

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Researchers set time limit for ultrafast perovskite solar cells September 22nd, 2017

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Physics

New quantum phenomena in graphene superlattices September 18th, 2017

Bit data goes anti-skyrmions September 1st, 2017

Heating quantum matter: A novel view on topology: Physicists demonstrate how heating up a quantum system can be used as a universal probe for exotic states of matter August 22nd, 2017

Sensing technology takes a quantum leap with RIT photonics research: Office of Naval Research funds levitated optomechanics project August 10th, 2017

Possible Futures

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Researchers set time limit for ultrafast perovskite solar cells September 22nd, 2017

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

Chip Technology

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

GLOBALFOUNDRIES Delivers 8SW RF SOI Technology for Next-Generation Mobile and 5G Applications: Advanced 8SW 300mm SOI technology enables cost-effective, high-performance RF front-end modules for 4G LTE mobile and sub-6GHz 5G applications September 20th, 2017

GLOBALFOUNDRIES Unveils Vision and Roadmap for Next-Generation 5G Applications: Technology platforms are uniquely positioned to enable a new era of ‘connected intelligence’ with the transition to 5G September 20th, 2017

Quantum Computing

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

First on-chip nanoscale optical quantum memory developed: Smallest-yet optical quantum memory device is a storage medium for optical quantum networks with the potential to be scaled up for commercial use September 11th, 2017

High-speed quantum memory for photons September 9th, 2017

Quantum detectives in the hunt for the world's first quantum computer September 8th, 2017

Optical computing/Photonic computing

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

First on-chip nanoscale optical quantum memory developed: Smallest-yet optical quantum memory device is a storage medium for optical quantum networks with the potential to be scaled up for commercial use September 11th, 2017

Discoveries

Quantum twisted Loong confirms the physical reality of wavefunctions September 23rd, 2017

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Researchers set time limit for ultrafast perovskite solar cells September 22nd, 2017

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Announcements

Quantum twisted Loong confirms the physical reality of wavefunctions September 23rd, 2017

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Researchers set time limit for ultrafast perovskite solar cells September 22nd, 2017

DNA triggers shape-shifting in hydrogels, opening a new way to make 'soft robots' September 21st, 2017

Photonics/Optics/Lasers

Quantum twisted Loong confirms the physical reality of wavefunctions September 23rd, 2017

Application of air-sensitive semiconductors in nanoelectronics: 2-D semiconductor gallium selenide in encapsulated nanoelectronic devices September 22nd, 2017

Physicists develop new recipes for design of fast single-photon gun Physicists develop high-speed single-photon sources for quantum computers of the future September 21st, 2017

A new approach to ultrafast light pulses: Unusual fluorescent materials could be used for rapid light-based communications systems September 19th, 2017

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project