CATCHING THE LIGHT: An entangled photon can be stored and then
retrieved from a solid-state memory, but hurdles remain before
the technology is ready for prime time. Image: Wolfgang
Tittel/University of Calgary Full-scale quantum computers, with
all the number crunching, code cracking and jaw-dropping
processing power researchers expect them to deliver, remain a
mere twinkle in the eye of physicists and computer scientists.
It is a twinkle supported by promising experimental and
theoretical work, but a twinkle nonetheless—to date only
rudimentary quantum processors have been built. Such computers
would harness the physical properties of quantum bits, or
qubits, to expand the reach of computation. Whereas ordinary
bits can be 0 or 1, a qubit can be in a superposition of 0 and 1
simultaneously—and qubits can be mutually entangled, meaning
that their properties are linked. Along the road to building a
full-fledged quantum computer lies a critical experimental
milestone that would be a significant achievement in