Implementing Finite Impulse Response Filters on Quantum Computers
Aishwarya Majumdar, Bojko N. Bakalov, Dror Baron, Yuan Liu
TL;DR
The paper builds a unified framework linking classical and quantum signal processing by encoding classical time-domain data into quantum states and implementing FIR filtering and filter cascading via carefully constructed block-encoded unitaries. It demonstrates how time-domain DSP concepts can translate to unitary quantum operations, and discusses strategies for both classical-to-quantum and quantum-to-classical processing, including practical simulation on IBM Qiskit and the challenges posed by noise and measurement. The work provides concrete design recipes for amplitude encoding, unitary realization of multi-tap filters, and cascading schemes, while identifying open problems such as circuit-depth, measurement for phase information, and efficient quantum-classical interfaces. Overall, this work lays a foundation for cross-fertilization of classical DSP and quantum algorithms, with potential speedups in domain-specific filtering tasks and a roadmap for extending quantum signal processing techniques to broader applications.
Abstract
While signal processing is a mature area, its connections with quantum computing have received less attention. In this work, we propose approaches that perform classical discrete-time signal processing using quantum systems. Our approaches encode the classical discrete-time input signal into quantum states, and design unitaries to realize classical concepts of finite impulse response (FIR) filters. We also develop strategies to cascade lower-order filters to realize higher-order filters through designing appropriate unitary operators. Finally, a few directions for processing quantum states on classical systems after converting them to classical signals are suggested for future work.
