论文标题

展示近期量子算法的连续一组两倍的门

Demonstrating a Continuous Set of Two-qubit Gates for Near-term Quantum Algorithms

论文作者

Foxen, B., Neill, C., Dunsworth, A., Roushan, P., Chiaro, B., Megrant, A., Kelly, J., Chen, Zijun, Satzinger, K., Barends, R., Arute, F., Arya, K., Babbush, R., Bacon, D., Bardin, J. C., Boixo, S., Buell, D., Burkett, B., Chen, Yu, Collins, R., Farhi, E., Fowler, A., Gidney, C., Giustina, M., Graff, R., Harrigan, M., Huang, T., Isakov, S. V., Jeffrey, E., Jiang, Z., Kafri, D., Kechedzhi, K., Klimov, P., Korotkov, A., Kostritsa, F., Landhuis, D., Lucero, E., McClean, J., McEwen, M., Mi, X., Mohseni, M., Mutus, J. Y., Naaman, O., Neeley, M., Niu, M., Petukhov, A., Quintana, C., Rubin, N., Sank, D., Smelyanskiy, V., Vainsencher, A., White, T. C., Yao, Z., Yeh, P., Zalcman, A., Neven, H., Martinis, John M.

论文摘要

量子算法为机器学习,材料科学和化学方面的计算问题提供了巨大的加速。但是,这些算法的任何近期实现都需要进行大量优化,以适合现有噪声量子硬件提供的有限资源。在这里,利用了GMON Qubit的强可调节耦合,我们演示了连续的两Q Quibent Gate组,与标准分解相比,电路深度的降低可以减少3倍。我们实施了两个门家族:类似于ISWAP的门,以达到任意交换角度,$θ$,以及生成任意条件阶段的CPHASE门,$ ϕ $。使用这些门之一,我们可以在激发传播的子空间内执行任意的两数Qubit门,从而可以完整实现所谓的费米子模拟或FSIM,GATE设置。我们基于类似ISWAP和CPHASE门家族的忠诚度以及525个其他FSIM大门在整个FSIM($θ$,$ ϕ $)的参数空间中均匀散布,可实现纯度纯度纯度的平均两倍的Pauli误差$ 3.8 \ times $ 3.8 \ times 10^{ - 3} $ per fsim Gate。

Quantum algorithms offer a dramatic speedup for computational problems in machine learning, material science, and chemistry. However, any near-term realizations of these algorithms will need to be heavily optimized to fit within the finite resources offered by existing noisy quantum hardware. Here, taking advantage of the strong adjustable coupling of gmon qubits, we demonstrate a continuous two-qubit gate set that can provide a 3x reduction in circuit depth as compared to a standard decomposition. We implement two gate families: an iSWAP-like gate to attain an arbitrary swap angle, $θ$, and a CPHASE gate that generates an arbitrary conditional phase, $ϕ$. Using one of each of these gates, we can perform an arbitrary two-qubit gate within the excitation-preserving subspace allowing for a complete implementation of the so-called Fermionic Simulation, or fSim, gate set. We benchmark the fidelity of the iSWAP-like and CPHASE gate families as well as 525 other fSim gates spread evenly across the entire fSim($θ$, $ϕ$) parameter space achieving purity-limited average two-qubit Pauli error of $3.8 \times 10^{-3}$ per fSim gate.

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