Electron ping-pong
29 Sep 2011 by Evoluted New Media
Scientists have been playing ping-pong with electrons in new research which reveals an important technique for transferring quantum information.
Researchers from the Cavendish Laboratory at the University of Cambridge have moved an individual electron along a wire, batting it back and forth over 60 times – just like a ball in a game of ping-pong. The research – published in Nature – may have applications in quantum computing, for example, transferring a quantum bit between processor and memory.
Electrons carrying a current along a wire do not travel directly from one end to the other – instead they follow a zigzagging path, which can be a problem if the electron is carrying information as the quantum state loses coherence.
Researchers trapped a single electron in a small well – a quantum dot – just inside the surface of a piece of gallium arsenide. A channel – which was higher in energy than the surrounding electrons –led to another empty dot four micrometres away. A very short burst of sound was sent along the surface, past the dot – its accompanying wave of electrical potential picked up the electron, which surfed along the channel to the other dot where it was captured before being sent back in the other direction.
“The movement of electrons by our ‘surface acoustic wave’ can be likened to peristalsis in the oesophagus, where food is propelled from the mouth to the stomach by wave of muscle contraction,” said Rob McNeil, a PhD student in the department of physics.
This is an enabling technology for quantum computers, said Chris Ford, team leader of the research from the Semiconductor Physics Group.
“There is a lot of work going on worldwide to make this new type of computer, which may solve certain complex problems much faster than classical computers,” he said. “However, little effort has been put into connecting up different components, such as a processor and memory.”
Although the experiments do not show that the electrons remember their quantum state, Ford expects this is likely to be the case, which would make this method a candidate for moving quantum bits of information – qubits – around a quantum circuit in a quantum computer.
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