Long live the qubit!

The power of quantum computers depends on keeping them in a fragile quantum-mechanical state - which researchers have found a new way to extend. A quantum computer is a device - still largely theoretical - that could perform some types of calculations much more rapidly than classical computers. While a bit in a classical computer can represent either 0 or 1, a quantum bit, or qubit, can be in 'superposition,' representing 0 and 1 at the same time. In experiments, however, keeping qubits in superposition long enough to do anything useful with them has proven very hard. In a paper slated for the July , researchers at MIT, MIT Lincoln Laboratory, Japan's Institute of Physical and Chemical Research and NEC describe a new technique that extends the time a qubit can stay in superposition. Perhaps even more important, the same technique can be used to measure the physical characteristics of qubits that knock them out of superposition in the first place, paving the way to better qubit designs. Researchers have sought to realize qubits in a variety of ways, from test tubes full of molecules sandwiched between powerful magnets to trapped ions manipulated by lasers.