arXiv:2603.13536quant-phcs.LG2026-03被引 3

用主动采样提升量子基态能量估算精度,避免全测量与冗余计算。

Active Sampling Sample-based Quantum Diagonalization from Finite-Shot Measurements

  • 将基态能量估算转化为主动学习问题,按物理重要性选择新增基态
  • 在16比特自旋链上误差比传统方法降低超50%,抗噪声能力强
  • 适合资源受限的近中期量子设备,尤其适用于含噪声硬件实验

近中期量子设备仅能进行有限次测量,且制备的量子态不完美、受污染。这促使我们发展一种无需完整量子态层析或全面测量的方法,仅通过样本即可获得可靠的低能估计。本文提出主动采样样本型量子对角化(AS-SQD),将SQD建模为一个主动学习问题:给定已测得的比特串,应添加哪些额外基态以高效恢复基态能量?标准SQD将哈密顿量限制在选定基态子空间内并经典对角化,但仅使用采样状态会因有限测量次数引入偏差和激发态污染,而盲目随机扩展效率随系统规模下降。我们引入基于埃普斯坦-内斯贝特二阶能量修正的摄动理论获取函数,用于评估与当前子空间相连的候选基态价值。每轮迭代中,AS-SQD对受限哈密顿量对角化,生成连接候选,并根据得分添加最有益项。我们在最多16量子比特的无序海森堡模型和横场伊辛模型上测试该方法,制备态含80%基态与20%第一激发态。此外,利用来自IBM量子处理器的真实物理样本验证了其对实际态制备与测量(SPAM)误差的鲁棒性。模拟与硬件测试均表明,AS-SQD在绝对能量误差上显著优于标准SQD与随机扩展。消融研究进一步证实,基于物理指导的基态选取能有效聚焦计算于能量相关方向,规避指数级组合瓶颈。

原文摘要 · Abstract (English)

Near-term quantum devices provide only finite-shot measurements and prepare imperfect, contaminated states. This motivates algorithms that convert samples into reliable low-energy estimates without full tomography or exhaustive measurements. We propose Active Sampling Sample-based Quantum Diagonalization (AS-SQD), framing SQD as an active learning problem: given measured bitstrings, which additional basis states should be included to efficiently recover the ground-state energy? SQD restricts the Hamiltonian to a selected set of basis states and classically diagonalizes the restricted matrix. However, naive SQD using only sampled states suffers from bias under finite-shot sampling and excited-state contamination, while blind random expansion is inefficient as system size grows. We introduce a perturbation-theoretic acquisition function based on Epstein--Nesbet second-order energy corrections to rank candidate basis states connected to the current subspace. At each iteration, AS-SQD diagonalizes the restricted Hamiltonian, generates connected candidates, and adds the most valuable ones according to this score. We evaluate AS-SQD on disordered Heisenberg and Transverse-Field Ising (TFIM) spin chains up to 16 qubits under a preparation model mixing 80\% ground state and 20\% first excited state. Furthermore, we validate its robustness against real-world state preparation and measurement (SPAM) errors using physical samples from an IBM Quantum processor. Across simulated and hardware evaluations, AS-SQD consistently achieves substantially lower absolute energy errors than standard SQD and random expansion. Detailed ablation studies demonstrate that physics-guided basis acquisition effectively concentrates computation on energetically relevant directions, bypassing exponential combinatorial bottlenecks.

量子算法主动学习能量估算噪声容忍

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