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arXiv · 2604.05452

A Digital Spreading Framework for Quantum Expectation Computation Without Rotation Gates or Arithmetic Circuits

Yu-Ting Kao·Yeong-Jar Chang
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Abstract

In the pursuit of quantum advantage for financial engineering, researchers face a critical dilemma: analog rotation gates suffer from inherent 'sine-to-square' biases and error magnification, while digital arithmetic circuits (e.g., WeightedAdder) incur prohibitive quadratic complexity that exceeds NISQ capabilities. This study introduces Digital Spreading (DS), a fully digital quantum computing framework designed to resolve this trade-off. DS overcomes these limitations by utilizing a pruned Cuccaro ripple-carry architecture that avoids costly multiplication and eliminates rotation gates entirely. The proposed circuit employs integer comparison operations on superposed quantum states, mapping multi-qubit outcomes onto the probability of a single target qubit. Experiments based on a random walk model for option pricing demonstrate that DS achieves floating-point precision with a relative error as low as 0.0001%, outperforming JP Morgan's rotation-based method (1.43%), as well as ITRI's analog calibration (1.43%) and digital calibration approaches (19.14%). Overall, DS provides a compact, robust, and accurate framework for quantum weighted-average computation.

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Yu-Ting Kao, Yeong-Jar Chang. 2026-04-07. A Digital Spreading Framework for Quantum Expectation Computation Without Rotation Gates or Arithmetic Circuits. https://arxiv.org/abs/2604.05452

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