High-Fidelity Continuous-Variable Quantum Teleportation Toward Multi-Step Quantum Operations

Progresses in quantum circuits of continuous variable (CV) schemes can be reduced to those in CV quantum teleportation. The fidelity of quantum teleportation of optical setup is limited by finite degree of quantum correlation which can be prepared with a pair of finitely squeezed states. A report of $-$9dB squeezing level has appeared recently, and we adopted the improved methods to our experimental system of quantum teleportation. As a result, we teleported a coherent state with a fidelity $F=0.83\pm 0.01$, which is better than any other figures reported to date. In this paper, we introduce a new measure $n_{s}$, the number of teleportations expected to be carried out sequentially. Our result corresponds to $n_{s}$=5.0$\pm$0.4. It suggests that our improvement would enable us to proceed toward more advanced quantum circuits involving multi-step quantum operations.