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arXiv · quant-ph/0606161

Exact and Approximate Unitary 2-Designs: Constructions and Applications

Christoph Dankert·Richard Cleve·Joseph Emerson·Etera Livine
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Abstract

We develop the concept of a unitary t-design as a means of expressing operationally useful subsets of the stochastic properties of the uniform (Haar) measure on the unitary group U(2^n) on n qubits. In particular, sets of unitaries forming 2-designs have wide applicability to quantum information protocols. We devise an O(n)-size in-place circuit construction for an approximate unitary 2-design. We then show that this can be used to construct an efficient protocol for experimentally characterizing the fidelity of a quantum process on n qubits with quantum circuits of size O(n) without requiring any ancilla qubits, thereby improving upon previous approaches.

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Christoph Dankert, Richard Cleve, Joseph Emerson, Etera Livine. 2006-06-20. Exact and Approximate Unitary 2-Designs: Constructions and Applications. https://doi.org/10.1103/physreva.80.012304

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