  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.
