Patent ID: 6974967

Claim:
A quantum logic gate utilizing an electronic state of a semiconductor quantum structure comprising: a first semiconductor quantum well structure as a control quantum bit; a second semiconductor quantum well structure as a target quantum bit having width which differs from width of the first semiconductor quantum well structure; a means for generating one exciton having an up spin or a down spin in the each first and second semiconductor quantum well structures; and a means for inverting the target quantum bit from |1> state to |0> state or from |0> state to |1> state only when the control quantum bit is in the |1> state by irradiating an electromagnetic wave corresponding to an shifted energy difference to the second semiconductor quantum well structure, where the |0> state in which the exciton is not excited and the |1> state is a state in which the exciton is excited for the each first and second semiconductor quantum well structures, wherein the shifted energy difference is shifted by an amount of a spin exchange interaction between the excitons undergone spin selective excitation, which occurs only when the exciton is generated simultaneously one by one both in the first and second semiconductor quantum well structures, from an energy difference between the |0> state and the |1> state without the spin exchange interaction.