使用具有相反符号非谐性的超导量子比特实现高对比度 ZZ 相互作用
High-contrast ZZ interaction using superconducting qubits with opposite-sign anharmonicity
AI总结：
提出耦合 transmon 与 C-shunt flux qubit 的相反符号非谐架构，实现高开关比 ZZ 相互作用，并抑制静态 ZZ 及旁观量子比特串扰。
摘要：
为构建可扩展的超导量子比特量子处理器，ZZ 相互作用备受关注，因为其残余相互作用对两量子比特门保真度具有关键影响。利用 ZZ 相互作用，保真度达到容错量子计算标准的两量子比特门已得到演示。然而，随着量子处理器性能提升，残余静态 ZZ 相互作用可能成为量子门操作和量子纠错的性能限制因素。在此，我们提出一种采用具有相反符号非谐性的量子比特的超导架构，即一个 transmon 量子比特和一个 C-shunt flux qubit（C 分流通量量子比特），以解决该问题。我们从理论上证明，通过耦合这两类量子比特，可以实现高对比度 ZZ 相互作用。因此，我们能够以高开关比控制该相互作用，以实现两量子比特 CZ 门；或者在利用 XY 相互作用进行两量子比特门操作（例如 iSWAP 门）期间抑制该相互作用。所提出的架构还可以扩展到多量子比特情形。在固定耦合系统中，与邻近旁观量子比特相关的 ZZ 串扰也可被大幅抑制。
英文摘要：
For building a scalable quantum processor with superconducting qubits, ZZ interaction is of great concern because its residual has a crucial impact to two-qubit gate fidelity. Two-qubit gates with fidelity meeting the criterion of fault-tolerant quantum computationhave been demonstrated using ZZ interaction. However, as the performance of quantum processors improves, the residual static-ZZ can become a performance-limiting factor for quantum gate operation and quantum error correction. Here, we introduce a superconducting architecture using qubits with opposite-sign anharmonicity, a transmon qubit and a C-shunt flux qubit, to address this issue. We theoretically demonstrate that by coupling the two types of qubits, the high-contrast ZZ interaction can be realized. Thus, we can control the interaction with a high on/off ratio to implement two-qubit CZ gates, or suppress it during two-qubit gate operation using XY interaction (e.g., an iSWAP gate). The proposed architecture can also be scaled up to multi-qubit cases. In a fixed coupled system, ZZ crosstalk related to neighboring spectator qubits could also be heavily suppressed.
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