Charge detection enables free-electron quantum computation

Abstract

The restoration of exponential speedup of quantum algorithms by the addition of single-charge measurements, was demonstrated. The single charge measurements enabled the construction of a CNOT gate for free fermions, using only beam splitters and spin rotations. The gate was fully deterministic if it only measured the parity of that number, and nearly deterministic if the charge detector counts the number of electrons in a mode. The results show that free-electron quantum computation is possible in principle, either nearly deterministically or exactly deterministically.