AI 中文总结
该研究在IBM量子处理器上发现，硬件连通性可反转三量子比特门精确分解的性能排序，含更多抽象两量子比特门的电路物理实现更优。
AI 中文摘要
精确的Toffoli门存在一种六-CX分解，记为$CCX_6$，该分解在无限制两量子比特连通性下是最优的。然而在线性三量子比特拓扑中，$CCX_6$包含4个近邻CX门和2个非近邻CX门。相比之下，另一种精确分解记为$CCX_8$，仅使用8个近邻CX门。由于CCZ与CCX局部等价，我们使用对应的$\text{CCZ}_S$和$\text{CCZ}_L$电路进行实验。我们在156量子比特的IBM量子Heron处理器\texttt{ibm_fez}和\texttt{ibm_kingston}的采样线性三量子比特组上比较这些电路。在编译协议下，标称的$\text{CCZ}_S$电路变为12-CZ实现，而线性近邻电路保留8个原生CZ门。实验测量的集成特征选择估计在几乎所有保留的三量子比特组上都倾向于8-CZ实现。我们通过制备三量子比特超图态来测试相同排序，该态探测相干条件相位而非仅计算基态布居。在两个处理器的大多数三量子比特组上，$\text{CCZ}_L$电路测量的超图态失保真度更低。相位改变的交错随机基准测试为保留两种编译纠缠结构的Clifford替代物提供了互补比较。在测试电路和相位敏感输入态的范围内，结果表明硬件连通性可反转精确分解的操作排序：具有更多抽象两量子比特门的电路可产生更优的物理实现。
英文摘要
The exact Toffoli gate admits a six-CX decomposition, denoted by $CCX_6$, that is optimal under unrestricted two-qubit connectivity. On a linear three-qubit topology, however, $CCX_6$ contains 4 nearest-neighbor CX gates and 2 non-nearest-neighbor CX gates. By contrast, an alternative exact decomposition, denoted by $CCX_8$, uses only 8 nearest-neighbor CX gates. Because CCX is locally equivalent to CCZ, we perform the experiments using the corresponding $\cczs$ and $\cczl$ circuits. We compare these circuits on sampled linear triples of the 156-qubit IBM Quantum Heron processors \texttt{ibm\_fez} and \texttt{ibm\_kingston}. Under the compilation protocol, the nominal $\cczs$ circuit becomes a twelve-CZ implementation, whereas the linear-nearest-neighbor circuit retains eight native CZ gates. Experimentally measured ensemble-feature-selection estimates favor the eight-CZ realization on nearly all retained triples. We test the same ordering by preparing a three-qubit hypergraph state, which probes the coherent conditional phase rather than only computational-basis populations. The measured hypergraph-state infidelity is lower for the $\cczl$ circuit for most triples on both processors. Phase-altered interleaved randomized benchmarking provides a complementary comparison of Clifford surrogates preserving the two compiled entangling structures. Within the scope of the tested circuits and phase-sensitive input state, the results demonstrate that hardware connectivity can reverse the operational ranking of exact decompositions: a circuit with more abstract two-qubit gates can yield the better physical implementation.
