TY  - JOUR
AU  - Müller, Thorge
AU  - Stollenwerk, Tobias
AU  - Headley, David
AU  - Epping, Michael
AU  - Wilhelm, Frank K
TI  - Coherent and non-unitary errors in ZZ-generated gates
JO  - Quantum science and technology
VL  - 10
IS  - 1
SN  - 2058-9565
CY  - Philadelphia, PA
PB  - IOP Publishing
M1  - FZJ-2025-01837
SP  - 015058 -
PY  - 2025
AB  - Variational algorithms such as the quantum approximate optimization algorithm have attracted attention due to their potential for solving problems using near-term quantum computers. The ZZ interaction typically generates the primitive two-qubit gate in such algorithms applied for a time, typically a variational parameter, γ. Different compilation techniques exist with respect to the implementation of two-qubit gates. Due to the importance of the ZZ-gate, we present an error analysis comparing the continuous-angle controlled phase gate (CP) against the fixed angle controlled Z-gate (CZ). We analyze both techniques under the influence of coherent over-rotation and depolarizing noise. We show that CP and CZ compilation techniques achieve comparable ZZ-gate fidelities if the incoherent error is below 0.03% and the coherent error is below 0.8%. Thus, we argue that for small coherent and incoherent error a non-parameterized two-qubit gate such as CZ in combination with virtual Z decomposition for single-qubit gates could lead to a significant reduction in the calibration required and, therefore, a less error-prone quantum device. We show that above a coherent error of 0.04π (2%), the CZ gate fidelity depends significantly on γ.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:001388382800001
DO  - DOI:10.1088/2058-9565/ad9be2
UR  - https://juser.fz-juelich.de/record/1040323
ER  -