A quantum computer will need a method to perform logic operations on qubits that are physically distant. Gate teleportation, proposed 20 years ago,1 does just that. It takes an approach similar to teleporting a qubit (see the article by Charles Bennett, Physics Today, October 1995, page 24) and uses entangled particles, or messengers, to teleport a logic gate that executes the operation. The messengers are entangled beforehand, and each one travels to a qubit and ropes it into the entangled state. Gate teleportation may also help deal with error propagation (see the article by John Preskill, Physics Today, June 1999, page 24).
In a modern classical computer, a switch uses many electrons, N ~ 105 or more. Provided the number of electrons doesn’t deviate by more than , the gate works flawlessly—typical failure rates are less than 10−18. In a...
