Photon-transistors for the supercomputers of the future

Aug 26, 2007
Photon-transistors for the supercomputers of the future
Two photons are sent through a nanowire towards an atom, where they collide, such that one photon (red) transfers its information to the other photon. Credit: Anders Søndberg Sørensen, associate professor, University of Copenhagen

Scientist from the Niels Bohr Institute at University of Copenhagen and from Harvard University have worked out a new theory which describe how the necessary transistors for the quantum computers of the future may be created. The research has just been published in the scientific journal Nature Physics.

Researchers dream of quantum computers. Incredibly fast super computers which can solve such extremely complicated tasks that it will revolutionise the application possibilities. But there are some serious difficulties. One of them is the transistors, which are the systems that process the signals.

Today the signal is an electrical current. For a quantum computer the signal can be an optical one, and it works using a single photon which is the smallest component of light.

“To work, the photons have to meet and “talk”, and the photons very rarely interact together” says Anders Søndberg Sørensen who is a Quantum Physicist at the Niels Bohr Institute at Copenhagen University. He explains that light does not function like in Star Wars, where the people fight with light sabres and can cross swords with the light. That is pure fiction and can’t happen. When two rays of light meet and cross, the two lights go right through each other. That is called linear optics.

What he wants to do with the light is non-linear optics. That means that the photons in the light collide with each other and can affect each other. This is very difficult to do in practice. Photons are so small that one could never hit one with the other. Unless one can control them – and it is this Anders Sørensen has developed a theory about.

Light collisions at the quantum level

Instead of shooting two photons at each other from different directions and trying to get them to hit each other, he wants to use an atom as an intermediary. The atom can only absorb one photon (such are the laws of physics). If you now direct two photons towards the atom it happens that they will collide on the atom. It is exactly what he wants.

The atom is however very small and difficult to hit. So the photons have to be focussed very precisely. In a previous experiment researchers had discovered that microwaves could be focussed on an atom via a superconducting nano-wire. They got the idea that the same could happen with visible light.

The theoretical model shows that it works. The atom is brought close to the nanowire. Two photons are sent towards the atom and when they hit it an interaction occurs between them, where one imparts information to the other. The information is sent in bits which are either a one or zero digit, and the order of digits produces the message. (Today we can send information via an optic cable and each bit is made up of millions of photons.) In quantum optics each bit is just one photon. The photon has now received its message and the signal continues on its way. It is a step on the way to building a photon-transistor for a quantum computer.

Source: University of Copenhagen

Explore further: Chemist develops X-ray vision for quality assurance

add to favorites email to friend print save as pdf

Related Stories

Boosting the force of empty space

5 hours ago

Vacuum fluctuations may be among the most counter-intuitive phenomena of quantum physics. Theorists from the Weizmann Institute (Rehovot, Israel) and the Vienna University of Technology propose a way to amplify ...

Quantum tech disappoints, but only because we don't get it

Jul 16, 2014

Over the next five years, the UK government will spend £270m on supporting research in "quantum technology". When budget announcements were made in 2013, provisions for offshore wind and shale gas extraction were received ...

Scientists track quantum errors in real time

Jul 14, 2014

( —Scientists at Yale University have demonstrated the ability to track real quantum errors as they occur, a major step in the development of reliable quantum computers. They report their results ...

The world's first photonic router

Jul 14, 2014

Weizmann Institute scientists have demonstrated for the first time a photonic router – a quantum device based on a single atom that enables routing of single photons by single photons. This achievement, ...

From pencil marks to quantum computers

Jul 03, 2014

Pick up a pencil. Make a mark on a piece of paper. Congratulations: you are doing cutting-edge condensed matter physics. You might even be making the first mark on the road to quantum computers, according ...

Recommended for you

New approach to form non-equilibrium structures

8 hours ago

Although most natural and synthetic processes prefer to settle into equilibrium—a state of unchanging balance without potential or energy—it is within the realm of non-equilibrium conditions where new possibilities lie. ...

Nike krypton laser achieves spot in Guinness World Records

10 hours ago

A set of experiments conducted on the Nike krypton fluoride (KrF) laser at the U.S. Naval Research Laboratory (NRL) nearly five years ago has, at long last, earned the coveted Guinness World Records title for achieving "Highest ...

Chemist develops X-ray vision for quality assurance

14 hours ago

It is seldom sufficient to read the declaration of contents if you need to know precisely what substances a product contains. In fact, to do this you need to be a highly skilled chemist or to have genuine ...

The future of ultrashort laser pulses

14 hours ago

Rapid advances in techniques for the creation of ultra-short laser pulses promise to boost our knowledge of electron motions to an unprecedented level.

IHEP in China has ambitions for Higgs factory

Jul 23, 2014

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

User comments : 0