August 11, 2005, Boulder, CO--Physicists at the National Institute of Standards and Technology (NIST) have used ions to demonstrate a quantum physics version of computer memory lasting longer than 10 seconds, more than 100,000 times longer than in previous experiments on the same ions.
As described in the Aug. 5, 2005, issue of Physical Review Letters, NIST scientists stored information in single beryllium ions for longer periods of time by using a different pair of the ions' internal energy levels to represent 1 and 0 than was used in the group's previous quantum computing experiments. This new set of quantum states is unaffected by slight variations in magnetic fields, which previously caused memory losses in ions stored in electromagnetic traps.
The new approach enables qubits to maintain superpositions over 1 million times longer than might be needed to carry out the information processing steps in a future quantum computer. The advance is, therefore, an important step toward the goal of designing a "fault tolerant" quantum computer because it significantly reduces the computing resources needed to correct memory errors.
In related experiments also described in the paper, NIST scientists demonstrated that pairs of entangled ions can retain their quantum states for up to about 7 seconds.