Simplifying Quantum Logic using Higher Dimensional Hilbert Spaces

by Benjamin Lanyon,......., and Andrew White

Quantum Computation promises to solve fundamental, yet otherwise intractable, problems across a range of active fields of research. Recently, universal quantum logic gate sets - the elemntal blocks for a quantum computer - have been demonstrated in several physical architectures. A serious obstacle to a full-scale implementation is the large number of these gates required to uild even small quantum circuits. Here, we present and demonstrate a general technique that harnesses multi-level information carriers to significantly reduce this number, enabling the construction of key quantum circuits with existing technology. we present implementations of two key quantum circuits: the three-qubit Toffoli gate and the general two-qubit controlled-unitary gate. Although our experiment is carried out in a phtonic architecture, the technique is independent of the particular physical encoding of quantum information, and has the potential for wider application.

**Groupmeeting by Hoda Hossein-Nejad**