Simplifying quantum logic using higher-dimensional Hilbert spaces

Benjamin P. Lanyon, Marco Barbieri, Marcelo P. Almeida, Thomas Jennewein, Timothy C. Ralph, Kevin J. Resch, Geoff J. Pryde, Jeremy L. O'Brien, Alexei Gilchrist, Andrew G. White

Research output: Contribution to journalArticlepeer-review

572 Citations (Scopus)


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 elemental building 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 build 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 photonic architecture, the technique is independent of the particular physical encoding of quantum information, and has the potential for wider application.

Original languageEnglish
Pages (from-to)134-140
Number of pages7
JournalNature Physics
Issue number2
Publication statusPublished - Feb 2009
Externally publishedYes


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