Charge detection enables free-electron quantum computation

It is known that a quantum computer operating on electron-spin qubits with single-electron Hamiltonians and assisted by single-spin measurements can be simulated efficiently on a classical computer. We show that the exponential speed-up of quantum algorithms is restored if single-charge measurements are added. These enable the construction of a CNOT (controlled NOT) gate for free fermions, using only beam splitters and spin rotations. The gate is nearly deterministic if the charge detector counts the number of electrons in a mode, and fully deterministic if it only measures the parity of that number.

Source: arXiv:0401066v1 - http://arxiv.org/abs/quant-ph/0401066v1 PDF: https://arxiv.org/pdf/quant-ph/0401066v1 Original Link: http://arxiv.org/abs/quant-ph/0401066v1