Superconducting architecture demonstrating fast, tunable high-fidelity <i>CZ</i> gates with parametric control of <i>ZZ</i> coupling

Future quantum information processors require tunable coupling architectures that can produce high-fidelity logical gates between two or more qubits. Parametric coupling is a powerful technique for generating tunable interactions between many qubits. Here, we present a highly flexible parametric coupling scheme with superconducting qubits that provides complete removal of residual <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>Z</a:mi> <a:mi>Z</a:mi> </a:math> coupling and the implementation of driven SWAP or SWAP-free controlled- <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>Z</c:mi> </c:math> ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mi>C</e:mi> <e:mi>Z</e:mi> </e:math> ) gates. Our fully integrated two-dimensional on-chip coupler design is only weakly flux tunable, cancels static linear coupling between the qubits, avoids internal coupler dynamics or excitations, and is extensible to multiqubit circuit-QED systems. Exploring gate fidelity versus gate duration allows us to maximize two-qubit gate fidelity, while providing insights into possible error sources for these gates. Randomized benchmarking over several hours reveals that the parametric SWAP <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>C</g:mi> <g:mi>Z</g:mi> </g:math> gate achieves an average fidelity of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mn>99.44</i:mn> <i:mo>±</i:mo> <i:mn>0.09</i:mn> <i:mi mathvariant="normal">%</i:mi> </i:math> in a gate duration of 70 ns and that a dispersively driven parametric SWAP-free <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"> <l:mi>C</l:mi> <l:mi>Z</l:mi> </l:math> gate attains an average fidelity of <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"> <n:mn>99.47</n:mn> <n:mo>±</n:mo> <n:mn>0.07</n:mn> <n:mi mathvariant="normal">%</n:mi> </n:math> in only 30 ns. The fidelity remained above this value for over 8 h and peaked twice with a maximum of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"> <q:mn>99.67</q:mn> <q:mo>±</q:mo> <q:mn>0.14</q:mn> <q:mi mathvariant="normal">%</q:mi> </q:math> . Overall, our parametric approach combines versatility, precision, speed, and high performance in one compact coupler design.