Use of Electron Paramagnetic resonance (EPR) technique to build quantum computers: n-qubit (n=1,2,3,4) Toffoli Gates

Abstract

It is shown theoretically how to use the EPR (Electron Paramagnetic Resonance) technique, using electron spins as qubits, coupled with each other by the exchange interaction, to set the configuration of n qubits (n=1,2,3,4) at resonance, in conjunction with pulses, to construct the NOT (one qubit), CNOT (two qubits), CCNOT (three qubits), CCCNOT (four qubits) Toffoli gates, which can be exploited to build a quantum computer. This is unique to EPR, wherein exchange-coupled electron spins are used. This is not possible with NMR (Nuclear Magnetic Resonance), that uses nuclear spins as qubits, which do not couple with each other by the exchange interaction.