Albert Einstein got many concepts brilliantly right in his time, but he turned out to be dead wrong about quantum entanglement. In the 1970s, physicist Alan Aspect successfully ran a version of the EPR experiment stretched across a space the size of a basketball court and showed that quantum entanglement in fact does exist. With this one experiment, the possibility of building a quantum computer seized the imagination of physicists. Current computers are limited by the speed of electrons as they whiz through a microprocessor chip; future optically-based computers now under development will be limited by the speed of light whizzing through their crystals. A computer based on quantum entanglement would have no limits at all on how fast it could perform logical switching operations since it would use “spooky action at a distance” instead of electrons or light. Even the most rabid computer gamer would be satisfied at last.
Just like you don’t have to understand cars to drive one to work tomorrow, you don’t have to “understand” quantum entanglement to use it in creating a computer building block. That’s just what Andrew Berkley and colleagues from the University of Maryland Center for Superconductivity Research have done. They have build a solid-state “chip” that has sucessfully stored two “particles” almost a millimeter apart in a quantum-entangled state. A millimeter of separation may not sound like much, and it certainly isn’t “opposite ends of the universe” – but it’s thousands of times farther apart than previous experiments have sustained entanglement and points the way to the building of true quantum computer components. If nothing else, Berkley’s chip runs a version of the EPR experiment in a space that’s much smaller than Aspect’s basketball court. This is a major step forward, covered in the pages of this week’s Science magazine and a few months ago in the journal Quantum Physics.