Quantum computing with an electron spin ensemble

We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium.~ Communication between spins is enabled by locating them in the vicinity of a stripline cavity, and making use of their strong~collective coupling to the quantized radiation field. The transformation between different spin waves is achieved by applying gradient magnetic fields across the sample, while a Cooper Pair Box,~ resonant with the cavity field, may be used to carry out one- and~ two-qubit gate operations. In the presentation we will address the achievable number of bits and number of gates with current measured and estimated physical parameters.