Quantum physicists control supercurrent

Aug 10, 2006

Netherlands scientists say they've shown that in a quantum-mechanical circuit, the current can be reversed by using a single electron.

The researchers led by Leo Kouwenhoven from the Delft University of Technology created a superconducting quantum interference device, or SQUID, and discovered they could reverse the current by placing an electron on a "weak link" where the current has to jump across a kind of barrier.

In the SQUID made by Kouwenhoven's team the current circulates around a ring-shaped circuit made from microscopic aluminum wire. There are two breaks in the loop, each bridged by wires just 60 nanometres wide and made from the semiconductor indium arsenide. At very low temperatures the aluminum becomes superconducting and the current is carried by pairs of electrons with zero electrical resistance.

The team used electric fields to turn the semiconductor nanowires into "quantum dots" -- isolated islands of electrical charge. Electron pairs can jump to and from the islands, so the supercurrent becomes chopped into discrete parcels of two electrons.

By adding just one electron to the quantum dot the researchers found they could reverse the direction of the supercurrent.

The physics are explained in the journal Nature.

Copyright 2006 by United Press International

Explore further: Superconducting circuits, simplified

add to favorites email to friend print save as pdf

Related Stories

Plastic nanoparticles also harm freshwater organisms

21 minutes ago

Organisms can be negatively affected by plastic nanoparticles, not just in the seas and oceans but in freshwater bodies too. These particles slow the growth of algae, cause deformities in water fleas and impede communication ...

Atomic trigger shatters mystery of how glass deforms

23 minutes ago

Throw a rock through a window made of silica glass, and the brittle, insulating oxide pane shatters. But whack a golf ball with a club made of metallic glass—a resilient conductor that looks like metal—and the glass not ...

US company sells out of Ebola toys

8 hours ago

They might look tasteless, but satisfied customers dub them cute and adorable. Ebola-themed toys have proved such a hit that one US-based company has sold out.

UN biodiversity meet commits to double funding

9 hours ago

A UN conference on preserving the earth's dwindling resources wrapped up Friday with governments making a firm commitment to double biodiversity aid to developing countries by 2015.

Recommended for you

Superconducting circuits, simplified

Oct 17, 2014

Computer chips with superconducting circuits—circuits with zero electrical resistance—would be 50 to 100 times as energy-efficient as today's chips, an attractive trait given the increasing power consumption ...

Protons hog the momentum in neutron-rich nuclei

Oct 16, 2014

Like dancers swirling on the dance floor with bystanders looking on, protons and neutrons that have briefly paired up in the nucleus have higher-average momentum, leaving less for non-paired nucleons. Using ...

Cosmic jets of young stars formed by magnetic fields

Oct 16, 2014

Astrophysical jets are counted among our Universe's most spectacular phenomena: From the centers of black holes, quasars, or protostars, these rays of matter sometimes protrude several light years into space. ...

User comments : 0