1. A method for optimal processing of a plurality of sets of coherent states of lights, the method comprising: receiving a light having a first coherent state out of a known set of 3 or more different coherent states; splitting the first coherent state of the received light into a plurality of slices of identical states, each of the plurality of slices of identical states being a coherent state of infinite dimensions with lower intensity than that of the first coherent state; transferring information of each of the plurality of slices of identical coherent states into a plurality of qubits, respectively; compressing quantum information of the plurality of qubits respectively including information of each of the plurality of slices of identical coherent states of infinite dimensions, into a quantum memory; and quantum processing the compressed quantum information from the quantum memory.