For building a scalable quantum processor with superconducting qubits, the ZZ interaction is of great concert because of relevant for implementing two-qubit gates, and the close contact between gate infidelity and its residual. Two-qubit gates with fidelity beyond fault-tolerant thresholds have been demonstrated using the ZZ interaction. However, as the performance of quantum processor improves, the residual static-ZZ can also become a performance-limiting factor for quantum gate operations and quantum error correction. Here, we introduce a scalable superconducting architecture for addressing this challenge. We demonstrate that by coupling two superconducting qubits with opposite-sign anharmonicities together, high-contrast ZZ interaction can be realized in this architecture. Thus, we can control ZZ interaction with high on/off ratio for implementing two-qubit CZ gate, or suppress it during the two-qubit gate operations using XY interaction (e.g. iSWAP). Meanwhile, the ZZ crosstalk related to neighboring spectator qubits can also be heavily suppressed in fixed coupled multi-qubit systems. This architecture could provide a promising way towards scalable superconducting quantum processor with high gate fidelity and low qubit crosstalk.For building a scalable quantum processor with superconducting qubits, the ZZ interaction is of great concert because of relevant for implementing two-qubit gates, and the close contact between gate infidelity and its residual. Two-qubit gates with fidelity beyond fault-tolerant thresholds have been demonstrated using the ZZ interaction. However, as the performance of quantum processor improves, the residual static-ZZ can also become a performance-limiting factor for quantum gate operations and quantum error correction. Here, we introduce a scalable superconducting architecture for addressing this challenge. We demonstrate that by coupling two superconducting qubits with opposite-sign anharmonicities together, high-contrast ZZ interaction can be realized in this architecture. Thus, we can control ZZ interaction with high on/off ratio for implementing two-qubit CZ gate, or suppress it during the two-qubit gate operations using XY interaction (e.g. iSWAP). Meanwhile, the ZZ crosstalk related to neighboring spectator qubits can also be heavily suppressed in fixed coupled multi-qubit systems. This architecture could provide a promising way towards scalable superconducting quantum processor with high gate fidelity and low qubit crosstalk.

Feb 18, 20201 citation

In situ Qubit Frequency Tuning Circuit for Scalable Superconducting Quantum Computing: Scheme and Experiment

Jiang, Lei, Yu Xu, Li, Shaowei +30 more

Frequency tunable qubit plays a significant role for scalable superconducting quantum processors. The state-of-the-art room-temperature electronics for tuning qubit frequency suffers from unscalable limit, such as heating problem, linear growth of control cables, etc. Here we propose a scalable scheme to tune the qubit frequency by using in situ superconducting circuit, which is based on radio frequency superconducting quantum interference device (rf-SQUID). We demonstrate both theoretically and experimentally that the qubit frequency could be modulated by inputting several single pulses into rf-SQUID. Compared with the traditional scheme, our scheme not only solves the heating problem, but also provides the potential to exponentially reduce the number of cables inside the dilute refrigerator and the room-temperature electronics resource for tuning qubit frequency, which is achieved by a time-division-multiplex (TDM) scheme combining rf-SQUID with switch arrays. With such TDM scheme, the number of cables could be reduced from the usual $\sim 3n$ to $\sim \log_2{(3n)} + 1$ for two-dimensional quantum processors comprising $n$ qubits and $\sim 2n$ couplers. Our work paves the way for large-scale control of superconducting quantum processor.Frequency tunable qubit plays a significant role for scalable superconducting quantum processors. The state-of-the-art room-temperature electronics for tuning qubit frequency suffers from unscalable limit, such as heating problem, linear growth of control cables, etc. Here we propose a scalable scheme to tune the qubit frequency by using in situ superconducting circuit, which is based on radio frequency superconducting quantum interference device (rf-SQUID). We demonstrate both theoretically and experimentally that the qubit frequency could be modulated by inputting several single pulses into rf-SQUID. Compared with the traditional scheme, our scheme not only solves the heating problem, but also provides the potential to exponentially reduce the number of cables inside the dilute refrigerator and the room-temperature electronics resource for tuning qubit frequency, which is achieved by a time-division-multiplex (TDM) scheme combining rf-SQUID with switch arrays. With such TDM scheme, the number of cables could be reduced from the usual $\sim 3n$ to $\sim \log_2{(3n)} + 1$ for two-dimensional quantum processors comprising $n$ qubits and $\sim 2n$ couplers. Our work paves the way for large-scale control of superconducting quantum processor.

arXiv:2407.21415Jul 31, 20241 citation

Superconducting qubits show promise

Barbara Goss Levi

Physics TodayJun 18, 20094 citations

Quantum computing with superconducting processors

Eyob Alebachew Sete

Apr 19, 20190 citations

\sim 3n

\sim \log_2{(3n)} + 1

for two-dimensional quantum processors comprising

n

qubits and

\sim 2n

couplers. Our work paves the way for large-scale control of superconducting quantum processor.