High-Performance Multi-Qubit System with Double-Transmon Couplers towards Scalable Superconducting Quantum Computers
arxiv(2024)
摘要
Tunable couplers in superconducting quantum computers have enabled fast and
accurate two-qubit gates, with reported high fidelities over 0.99 in various
architectures and gate implementation schemes. However, there are few tunable
couplers whose performance in multi-qubit systems is clarified, except for the
most widely used one: single-transmon coupler (STC). Achieving similar accuracy
to isolated two-qubit systems remains challenging due to various undesirable
couplings but is necessary for scalability. In this work, we numerically
analyze a system of three fixed-frequency qubits coupled via two
double-transmon couplers (DTCs) where nearest-neighbor qubits are highly
detuned and also next nearest-neighbor ones are nearly resonant. The DTC is a
recently proposed tunable coupler, which consists of two fixed-frequency
transmons coupled through a common loop with an additional Josephson junction.
We find that the DTC can not only reduce undesired residual couplings
sufficiently, as well as in isolated two-qubits systems, but also enables
implementations of 30-ns CZ gates and 10-ns π/2 pulses with fidelities of
0.9999 or higher. For comparison, we also investigate the system where the DTCs
are replaced by the STCs. The results show that the DTC outperforms the STC in
terms of both residual coupling suppression and gate accuracy in the above
systems. From these results, we expect that the DTC architecture is promising
for realizing high-performance, scalable superconducting quantum computers.
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