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Abstract: We introduce a new paradigm for quantum computing called Ancilla-DrivenQuantum Computation ADQC combines aspects of the quantum circuit and theone-way model to overcome challenging issues in building large-scale quantumcomputers. Instead of directly manipulating each qubit to perform universalquantum logic gates or measurements, ADQC uses a fixed two-qubit interaction tocouple the memory register of a quantum computer to an ancilla qubit. Bymeasuring the ancilla, the measurement-induced back-action on the systemperforms the desired logical operations.By demanding that the ancilla-system qubit interaction should lead to unitaryand stepwise deterministic evolution, and that it should be possible tostandardise the computation, that is, applying all global operations at thebeginning, we are able to place conditions on the interactions that can be usedfor ADQC. We prove there are only two such classes of interactionscharacterised in terms of the non-local part of the interaction operator. Thisleads to the definition of a new entanglement resource called twisted graphstates generated from non-commuting operators. The ADQC model is formalised inan algebraic framework similar to the Measurement Calculus. Furthermore, wepresent the notion of causal flow for twisted graph states, based on thestabiliser formalism, to characterise the determinism. Finally we demonstratecompositional embedding between ADQC and both the one-way and circuit modelswhich will allow us to transfer recently developed theory and toolkits ofmeasurement-based quantum computing directly into ADQC.

Author: Elham Kashefi, Daniel K. L. Oi, Daniel E. Browne, Janet Anders, Erika Andersson


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