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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.

Implementing Finite Impulse Response Filters on Quantum Computers

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.
Paper Structure (8 sections, 15 equations, 3 figures)

This paper contains 8 sections, 15 equations, 3 figures.

Figures (3)

  • Figure 1: Interconnections between various signal processing domains.
  • Figure 2: Various schemes for processing classical digital signals on quantum digital systems. a) classical to quantum signal conversion; b) time-domain processing to implement the filters on quantum computers; c) cascading two filters on quantum computers.
  • Figure 3: Simulation results for a symmetric 3-tap high pass filter with low and high-frequency signal at the input. b)-d) depict the output of the classical filter, ideal quantum filter and quantum machine-simulator quantum filter.