Stabilizing quantum bits
Quantum computers are largely hypothetical devices that could perform some calculations much more rapidly than conventional computers can. They exploit a property called superposition, which describes a quantum particle’s counterintuitive ability to, in some sense, inhabit more than one physical state at the same time. But superposition is fragile, and finding ways to preserve it is one of the chief obstacles to developing large, general-purpose quantum computers. In today’s Nature, MIT researchers describe a new approach to preserving superposition in a class of quantum devices built from synthetic diamonds. The work could ultimately prove an important step toward reliable quantum computers. In most engineering fields, the best way to maintain the stability of a physical system is feedback control. You make a measurement — the current trajectory of an airplane, or the temperature of an engine — and on that basis produce a control signal that nudges the system back toward its...