Realization of Scalable Cirac-Zoller Multi-Qubit Gates

The universality theorem in quantum computing states that any quantum computational task can be decomposed into a finite set of logic gates operating on one and two qubits [1]. The Cirac-Zoller gate is a protocol for realizing native multi-qubit controlled-Z gate utilizing spin interactions mediated by Coulomb-coupled collective motion of an ion crystal [2]. Despite being outperformed by the more popular Molmer-Sorensen (MS) gate at implementing the two-qubit controlled-NOT (CNOT) gate due to its more challenging technical requirements, the Cirac-Zoller gate scheme scales much more efficiently with the number of qubits. We demonstrate the Cirac-Zoller three-qubit and four-qubit quantum Toffoli gates in a five-ion chain with higher fidelities than previous results using trapped ions. We also report the first experimental realization of a five-qubit Toffoli gate.



Reference

1. Deutsch, David Elieser, Adriano Barenco, and Artur Ekert. "Universality in quantum computation." Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences 449, no. 1937 (1995): 669-677.

2. Cirac, Juan I., and Peter Zoller. "Quantum computations with cold trapped ions." Physical review letters 74, no. 20 (1995): 4091.