Novel approach of performing elementary quantum operations using spatial phase

We propose a new idea of generating and controlling quantum coherences among semiconductor quantum dots by using the spatial phase of one single-mode incident laser pulse. Two or three identical quantum dots are employed as qubit gates. Our strategy is to use the spatial phase of the laser pulse at the different positions of the qubits for quantum operations, rather than to utilize dipole-dipole interactions between them. In this work, Hadamard transformation and creation of entanglements in the bipartite and tripartite systems are examined. We predict that with much simpler experimental setup the spatial phase of the laser pulse makes it possible to perform elementary quantum operations that are infeasible by the present-day quantum computer architecture.