In contrast to conventional computers that are based on transistors with distinct “on” and “off” or “1” and “0” states, quantum computers are built from devices called qubits that exploit the quirky properties of quantum mechanics. Unlike a transistor, a qubit can represent a multiplicity of values simultaneously.
That might make it possible to factor large numbers more quickly than with conventional machines, thereby undermining modern data-scrambling systems that are the basis of electronic commerce and data privacy. Quantum computers might also make it possible to simulate molecular structures with great speed, an advance that holds promise for designing new drugs and other materials.
“Their approach is extremely powerful,” said Andreas Heinrich, a physicist at I.B.M. “This is at least a 10-year effort to make very tiny electrical wires and combine them with the placement of a phosphorus atom exactly where they want them.”