Ancilla-driven quantum computation for qudits and continuous variables

Proctor, Timothy and Giulian, Melissa and Korolkova, Natalia and Andersson, Erika and Kendon, Viv (2017) Ancilla-driven quantum computation for qudits and continuous variables. Physical Review A, 95 (5). 052317. ISSN 2469-9926 (https://doi.org/10.1103/PhysRevA.95.052317)

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Abstract

Although qubits are the leading candidate for the basic elements in a quantum computer, there are also a range of reasons to consider using higher-dimensional qudits or quantum continuous variables (QCVs). In this paper, we use a general "quantum variable" formalism to propose a method of quantum computation in which ancillas are used to mediate gates on a well-isolated "quantum memory" register and which may be applied to the setting of qubits, qudits (for d>2), or QCVs. More specifically, we present a model in which universal quantum computation may be implemented on a register using only repeated applications of a single fixed two-body ancilla-register interaction gate, ancillas prepared in a single state, and local measurements of these ancillas. In order to maintain determinism in the computation, adaptive measurements via a classical feed forward of measurement outcomes are used, with the method similar to that in measurement-based quantum computation (MBQC). We show that our model has the same hybrid quantum-classical processing advantages as MBQC, including the power to implement any Clifford circuit in essentially one layer of quantum computation. In some physical settings, high-quality measurements of the ancillas may be highly challenging or not possible, and hence we also present a globally unitary model which replaces the need for measurements of the ancillas with the requirement for ancillas to be prepared in states from a fixed orthonormal basis. Finally, we discuss settings in which these models may be of practical interest.

ORCID iDs

Proctor, Timothy, Giulian, Melissa, Korolkova, Natalia, Andersson, Erika and Kendon, Viv ORCID logoORCID: https://orcid.org/0000-0002-6551-3056;
CORE (COnnecting REpositories)