Mediated gates between spin qubits

Jianjia Fei, Dong Zhou, Yun Pil Shim, Sangchul Oh, Xuedong Hu, Mark Friesen

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7 Citations (Scopus)


In a typical quantum circuit, nonlocal quantum gates are applied to nonproximal qubits. If the underlying physical interactions are short-range (e.g., exchange interactions between spins), intermediate swap operations must be introduced, thus increasing the circuit depth. Here we develop a class of "mediated" gates for spin qubits, which act on nonproximal spins via intermediate ancilla qubits. At the end of the operation, the ancillae return to their initial states. We show how these mediated gates can be used (1) to generate arbitrary quantum states and (2) to construct arbitrary quantum gates. We provide some explicit examples of circuits that generate common states [e.g., Bell, Greenberger-Horne-Zeilinger (GHZ), W, and cluster states] and gates (e.g., √swap, swap, cnot, and Toffoli gates). We show that the depths of these circuits are often shorter than those of conventional swap-based circuits. We also provide an explicit experimental proposal for implementing a mediated gate in a triple-quantum-dot system.

Original languageEnglish
Article number062328
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number6
Publication statusPublished - 26 Dec 2012
Externally publishedYes


ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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