arXiv:2607.10772
Demonstrating Quadratic Monte Carlo Speedup via Quantum Amplitude Estimation: Nuclear Engineering Examples
Jilang Miao, Miaomiao Jin, Akira Sone
Abstract
We demonstrate quantum amplitude estimation (QAE) as a route to quadratic speedup for Monte Carlo-type expectation values in nuclear engineering. Using QPE-based QAE, we study two examples: a discrete fission-neutron-yield expectation and a U-238 resonance integral under a $1/E$ slowing-down spectrum. The toy problem is implemented as a gate-level Qiskit circuit, while the resonance-integral example is simulated through an exact eigendecomposition of the Grover operator to avoid state-preparation decomposition bottlenecks. In both cases, the squared error scales as $O(1/T^2)$ with the number of oracle calls $T$, compared with the classical Monte Carlo scaling $O(1/N)$. For the U-238 example, QAE recovers the resonance integral to approximately $0.03%$ relative error with $m=14$ phase-estimation qubits.
AI Summary
The paper studies QPE-based quantum amplitude estimation (QAE) for two nuclear-engineering expectation values, comparing estimation error against classical Monte Carlo sampling. It encodes a probability distribution and bounded scoring function into a state-preparation unitary, then estimates the associated Grover eigenphase using $m$ phase-estimation qubits and $T=2^m-1$ Grover-operator calls. The first example is a four-outcome fission-neutron-yield model with exact mean $\bar\nu=2$. Qiskit statevector simulations use $m=2$–$16$ and 8,192 shots per setting, decoding the most frequent phase-register outcome. The second example estimates a U-238 resonance integral around the 6.674 eV resonance, discretized into 256 energy bins under a $1/E$ spectrum. Rather than decomposing its state-preparation circuit, this example constructs a $512\times512$ Grover matrix and simulates QPE through exact eigendecomposition and Fourier transforms. Both examples report decoded squared errors consistent with $O(T^{-2})$, compared with classical Monte Carlo MSE $O(N^{-1})$. At $m=14$, the resonance estimate is 120.65 b versus a reference value of 120.69 b, approximately 0.03% relative error. The paper compares its squared amplitude error with approximately 49.4 million classical samples, yielding a nominal sample-to-oracle-call ratio of 3,016; each QAE setting nevertheless uses 8,192 shots. The stated implementation limitation is the cost of generic state-preparation decomposition, which prevents gate-level simulation of the larger example. The eigendecomposition surrogate reproduces the ideal measurement distribution but does not provide a hardware-ready circuit. Quantum-arithmetic state preparation, larger discretizations, multiple resonances, and iterative QAE are left for future work.
Central claim may not hold: The paper labels modal squared-error curves as MSE without establishing the mean squared error of its finite-shot mode estimator. The claimed approximately 3016-fold numerical speedup omits 8192 repetitions, which increase the implemented QAE cost to approximately 134.2 million Grover calls versus the quoted 49.4 million classical samples. The stated resonance parameters and discretization yield C_phys approximately 1587.86 b and μ approximately 0.076011, not the reported 1578 b and 0.07648.
Written by gpt-6.1-sol from the paper's full text. Automated: it can be wrong.
- Comments
- 4 pages,3 figures, submitted to 2026 ANS Annual Conference