A quantum approach for digital signal processing

TL;DR

This paper introduces a quantum signal processing method using sequency-ordered Walsh-Hadamard transforms, offering faster filtering algorithms with reduced circuit complexity compared to classical and other quantum methods.

Contribution

It presents a novel quantum algorithm and circuits for signal filtering based on Walsh-Hadamard transforms, with improved efficiency over existing quantum Fourier and classical FFT methods.

Findings

Quantum circuits for Walsh-Hadamard transform and filtering demonstrated.

Reduced gate complexity and circuit depth of O(log N) achieved.

Significant speedup over classical FFT and QFT-based filtering methods.

Abstract

We propose a novel quantum approach to signal processing, including a quantum algorithm for low-pass and high-pass filtering, based on the sequency-ordered Walsh-Hadamard transform. We present quantum circuits for performing the sequency-ordered Walsh-Hadamard transform, as well as quantum circuits for low-pass, high-pass, and band-pass filtering. Additionally, we provide a proof of correctness for the quantum circuit designed to perform the sequency-ordered Walsh-Hadamard transform. The performance and accuracy of the proposed approach for signal filtering were illustrated using computational examples, along with corresponding quantum circuits, for DC, low-pass, high-pass, and band-pass filtering. Our proposed algorithm for signal filtering has a reduced gate complexity and circuit depth of $O (\log_2 N)$, compared to at least $O ((\log_2 N )^2)$ associated with Quantum Fourier Transform (QFT) based filtering (excluding state preparation and measurement costs). In contrast, classical Fast Fourier Transform (FFT) based filtering approaches have a complexity of $O (N \log_2 N )$. This shows that our proposed approach offers a significant improvement over QFT-based filtering methods and classical FFT-based filtering methods. Such enhanced efficiency of our proposed approach holds substantial promise across several signal processing applications by ensuring faster computations and efficient use of resources via reduced circuit depth and lower gate complexity.