arXiv:2602.05058quant-phcs.DS2026-02被引 2

首次实现满足物理规律的费米子线性光学高效学习,精度达海森堡极限。

Learning fermionic linear optics with Heisenberg scaling and physical operations

  • 基于最小辅助模式,设计符合费米子守恒规则的学习算法。
  • 主动型FLO学习仅需$\widetilde{\mathcal{O}}(n^4 / \varepsilon)$查询,被动型仅需$\mathcal{O}(n^3 / \varepsilon)$。
  • 首次达到海森堡精度标度,适合量子模拟与实验验证。

我们重新研究了费米子线性光学(FLO)的学习问题,即费米子高斯幺正操作。以往方法需$\widetilde{\mathcal{O}}(n^5 / \varepsilon^2)$次黑箱查询,且使用非物理操作或$ n $个辅助模式准备乔伊态。本文提出高效且实验友好的协议:遵守超选择规则,最多仅用1个额外模式。对于任意(主动)FLO,查询次数不超过$\widetilde{\mathcal{O}}(n^4 / \varepsilon)$;对于数守恒(被动)FLO,$\mathcal{O}(n^3 / \varepsilon)$次查询已足够。若允许使用$ n $个辅助模式,主动情形可进一步优化至$\widetilde{\mathcal{O}}(n^3 / \varepsilon)$。这是首个实现精度海森堡标度的FLO学习算法。作为副成果,我们还证明了对$ η $粒子斯莱特行列式进行时间高效的态层析,其复制复杂度为$\widetilde{\mathcal{O}}(n η^2 / \varepsilon^2)$,在$ \varepsilon $迹距离下成立,可能具有独立意义。

原文摘要 · Abstract (English)

We revisit the problem of learning fermionic linear optics (FLO), also known as fermionic Gaussian unitaries. Given black-box query access to an unknown FLO, previous proposals required $\widetilde{\mathcal{O}}(n^5 / \varepsilon^2)$ queries, where $n$ is the system size and $\varepsilon$ is the error in diamond distance. These algorithms also use unphysical operations (i.e., violating fermionic superselection rules) and/or $n$ auxiliary modes to prepare Choi states of the FLO. In this work, we establish efficient and experimentally friendly protocols that obey superselection, use minimal ancilla (at most $1$ extra mode), and exhibit improved dependence on both parameters $n$ and $\varepsilon$. For arbitrary (active) FLOs this algorithm makes at most $\widetilde{\mathcal{O}}(n^4 / \varepsilon)$ queries, while for number-conserving (passive) FLOs we show that $\mathcal{O}(n^3 / \varepsilon)$ queries suffice. The complexity of the active case can be further reduced to $\widetilde{\mathcal{O}}(n^3 / \varepsilon)$ at the cost of using $n$ ancilla. This marks the first FLO learning algorithm that attains Heisenberg scaling in precision. As a side result, we also demonstrate an improved copy complexity of $\widetilde{\mathcal{O}}(n η^2 / \varepsilon^2)$ for time-efficient state tomography of $η$-particle Slater determinants in $\varepsilon$ trace distance, which may be of independent interest.

量子学习费米子系统海森堡极限量子模拟

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