Constructing a virtual two-qubit gate from single-qubit operations

  • Kosuke Mitarai
  • ,
  • Keisuke Fujii

We show a certain kind of non-local operations can be decomposed into a
sequence of local operations. Utilizing the result, we describe a strategy to
decompose a general two-qubit gate to a sequence of single-qubit operations.
Required operations are projective measurement of a qubit in Pauli basis, and
$\pi/2$ rotation around x, y, and z axes. The required number of circuit runs
to get an expectation value of a target observable within an error of
$\epsilon$ is roughly $O(9^k/\epsilon^2)$, where $k$ is the number of ``cuts''
performed. The proposed technique enables to perform ``virtual'' gates between
a distant pair of qubits, where there is no direct interaction and thus a
number of swap gates are inevitable otherwise. It can also be utilized to
improve the simulation of a large quantum computer with a small-sized quantum
device, which is an idea put forward by [Peng, et al., arXiv:1904.00102]. This
work can enhance the connectivity of qubits on near-term, noisy quantum

Arxiv Url
Arxiv Url
http://arxiv.org/pdf/1909.07534v1 本文へのリンクあり