Abstract
A controlled-phase gate was demonstrated in superconducting Xmon transmon qubits with fidelity reaching 99.4%, relying on the adiabatic interaction between the and states. Here we explain the theoretical concepts behind this protocol, which achieves fast gate times with only control of the Hamiltonian, based on a theory of nonlinear mapping of state errors to a power spectral density and use of optimal window functions. With a solution given in the Fourier basis, optimization is shown to be straightforward for practical cases of an arbitrary state change and finite bandwidth of control signals. We find that errors below are readily achievable for realistic control wave forms.
- Received 21 February 2014
DOI:https://doi.org/10.1103/PhysRevA.90.022307
©2014 American Physical Society