论文标题
近期量子硬件的迭代量子估计协议
An iterative quantum-phase-estimation protocol for near-term quantum hardware
论文作者
论文摘要
给定的$ n _ {\ textrm {tot}} $应用单位操作的应用，具有未知阶段$θ$，一个大尺度耐故障的量子系统可以{降低}估算{error}从$ \ nathcal {o} $ \ Mathcal {O} \ left [1 / {n _ {\ textrm {tot}}}}} \ right] $。由于近期量子设备可用的资源有限，因此已经开发了无纠缠的协议，该协议实现了$ \ Mathcal {o} \ left [\ log（n _ {\ textrm {tot}}}） / n _ {\ textrm {textrm {tot}}}} \ right] $ {eye-absolute-orr}。在这里，我们为近期阶段估计提出了一个新的两步协议，并进行了改进的{error}缩放。我们的协议的第一步在$θ$的参数范围内产生了$θ$的几个低 - {标准 - 解答}。第二步是在这些估计之一上迭代磨练的。我们的协议的{Mean绝对错误}将缩放为$ \ Mathcal {o} \ left [\ sqrt {\ log（\ log n _ {\ textrm {tot}}}} / n _ {\ textrm {textrm {tot}}}}} \ right] $。此外，我们证明了恒定缩放系数和所需的电路深度的减少：我们的协议可以超过$ n _ {\ textrm {tot}} $的现实值的渐近最佳量子相估计算法。
Given $N_{\textrm{tot}}$ applications of a unitary operation with an unknown phase $θ$, a large-scale fault-tolerant quantum system can {reduce} an estimate's {error} scaling from $\mathcal{O} \left[ 1 / \sqrt{N_{\textrm{tot}}} \right]$ to $\mathcal{O} \left[ 1 / {N_{\textrm{tot}}} \right]$. Owing to the limited resources available to near-term quantum devices, entanglement-free protocols have been developed, which achieve a $\mathcal{O} \left[ \log(N_{\textrm{tot}}) / N_{\textrm{tot}} \right]$ {mean-absolute-error} scaling. Here, we propose a new two-step protocol for near-term phase estimation, with an improved {error} scaling. Our protocol's first step produces several low-{standard-deviation} estimates of $θ$, within $θ$'s parameter range. The second step iteratively hones in on one of these estimates. Our protocol's {mean absolute error} scales as $\mathcal{O} \left[ \sqrt{\log (\log N_{\textrm{tot}})} / N_{\textrm{tot}} \right]$. Furthermore, we demonstrate a reduction in the constant scaling factor and the required circuit depths: our protocol can outperform the asymptotically optimal quantum-phase estimation algorithm for realistic values of $N_{\textrm{tot}}$.
