Distance-Independent Quantum CNOT Operation via Intermediate Measurements*

Quantum computers are fast approaching their potential to solve certain important problems in physics and chemistry.  The problem size we can solve accurately, however, is bounded by low qubit coherence time.  This time constraint is a major challenge.  Consequently, programs are highly optimized to reduce duration and improve accuracy.  Computer scientists have made significant progress in these optimization tools, enabling us to solve somewhat larger problems.    However, with only optimization, we cannot overcome fundamental barriers.

For instance, we perform a long-distance operation today by first moving quantum information into neighboring qubits but this movement wastes time proportional to the movement distance.  We present an alternative method to perform long-distance qubit operations in constant time.  Our method has the potential to enable larger problems to be solved within the coherence limit now that industry has begun to enable fast qubit measurement during computation.  We combine fast measurements with a protocol based on quantum gate teleportation to perform fast, distance-independent CNOTs and more.