Quantum computers have the potential to solve problems much faster than normal or 'classical' computers by exploiting the ability of particles to be in two or more quantum states at the same time. However, most practical proposals for quantum computers are currently limited to about ten particles or "qubits" - which is too few for meaningful computation. Now Ignacio Cirac and Peter Zoller from the University of Innsbruck in Austria have proposed a scalable quantum computer that could contain many more qubits (Nature 404 579)
The Innsbruck model relies on ions stored in an array of microtraps. Because the microtraps can be fabricated in a solid state device, thousands of traps can be put into an array. The internal quantum state of the ions acts as the qubit. A different ion, called the head ion, moves above the array to read the information stored by the trapped ions. A laser beam directed at the head ion causes it to move, which leads to an interaction with one of the ions in the array.
According to Cirac and Zoller, the method combines the scalability associated with the solid-state approach to quantum computing with the control found in quantum optical systems, such as photons and ions in traps.
