A functional basis for efficient physical-layer classical control in quantum processors

TL;DR

This paper introduces a scalable, resource-efficient framework for classical control in quantum processors using Walsh functions, enabling real-time FPGA implementation for error suppression and noise characterization.

Contribution

It proposes Walsh functions as a functional basis for physical-layer control, facilitating scalable and efficient classical-quantum interface design in quantum computing.

Findings

Successfully implemented FPGA-based Walsh controller for real-time control signals

Demonstrated Walsh functions' effectiveness in error suppression and noise characterization

First experimental realization of a unified physical-layer control framework

Abstract

The rapid progress seen in the development of quantum coherent devices for information processing has motivated serious consideration of quantum computer architecture and organization. One topic which remains open for investigation and optimization relates to the design of the classical-quantum interface, where control operations on individual qubits are applied according to higher-level algorithms; accommodating competing demands on performance and scalability remains a major outstanding challenge. In this work we present a resource-efficient, scalable framework for the implementation of embedded physical-layer classical controllers for quantum information systems. Design drivers and key functionalities are introduced, leading to the selection of Walsh functions as an effective functional basis for both programming and controller hardware implementation. This approach leverages the simplicity of real-time Walsh-function generation in classical digital hardware, and the fact that a wide variety of physical-layer controls such as dynamic error suppression are known to fall within the Walsh family. We experimentally implement a real-time FPGA-based Walsh controller producing Walsh timing signals and Walsh-synthesized analog waveforms appropriate for critical tasks in error-resistant quantum control and noise characterization. These demonstrations represent the first step towards a unified framework for the realization of physical-layer controls compatible with large-scale quantum information processing.