Coherent-state linear optical quantum computing gates using simplified diagonal superposition resource states
Austin P. Lund, Timothy C. Ralph · Physical Review A · 2005
In this paper we explore the possibility of fundamental tests for coherent-state optical quantum computing gates [T. C. Ralph et al., Phys. Rev. A 68, 042319 (2003)] using sophisticated but not unrealistic quantum states. The major resource required in these gates is a state diagonal to the basis states. We use the recent observation that a squeezed single-photon state $[S(r)\ensuremath{\mid}1⟩]$ approximates well an odd superposition of coherent states $(\ensuremath{\mid}\ensuremath{\alpha}⟩\ensuremath{-}\ensuremath{\mid}\ensuremath{-}\ensuremath{\alpha}⟩)$ to address the diagonal resource problem. The approximation only holds for relatively small $\ensuremath{\alpha}$, and hence these gates cannot be used in a scalable scheme. We explore the effects on fidelities and probabilities in teleportation and a rotated Hadamard gate.