QUANTUM LOGIC

This invention concerns a method to switch on and off the exchange interaction J between electron spins bound to donor atoms. The electron spins have the role of ‘qubits’ to carry quantum information, and the exchange interaction J has the role of mediator for two-qubit quantum logic operations. The invention aims at exploiting the existence of a further magnetic interaction, the hyperfine interaction A, between each electron spin and the nuclear spin of the donor atom (301, 302) that binds the electron. The hyperfine interaction A, together with the ability to read out (504) and control the state of the nuclear spins, is used to suppress the effect of the exchange interaction J at all times, except while a quantum logic operation is being performed. In this way, the result of the quantum logic operation is not distorted after the operation has taken place. In a further aspect, the invention concerns an electronic device where the method can be practically implemented, and a large scale device made up of many of the devices.