Running large quantum circuits on small quantum computers

With the advent of NISQ computers, the question of running quantum programs whose number of qubits exceeds the capacity of today’s small processors becomes pressing. In this work, we have implemented a recent theoretical proposal [1] consisting in splitting a large circuit into smaller fragments that can be run on smaller processors. As a test case, we have taken circuits used by the quantum approximate approximation algorithm (QAOA [2]) to solve combinatorial optimization problems. We have implemented, run and assessed the method on the IBM Poughkeepsie 20-qubit superconducting quantum processor, and have compared the obtained results with simulations in the presence of noise that we characterized via tomography.

[1] T. Peng, A. Harrow, M. Ozols, and X. Wu, arxiv: 1904.00102 (2019).
[2] E. Farhi, J. Goldstone, and S. Gutmann, arxiv: 1411.4028 (2014).