  Execution of quantum algorithms requires a quantum computer architecture with
a dedicated quantum instruction set that is capable of supporting translation
of workloads into actual quantum operations acting on the qubits.
State-of-the-art qubit control setups typically utilize general purpose test
instruments such as arbitrary waveform generators (AWGs) to generate a limited
set of waveforms or pulses. These waveforms are precomputed and stored prior to
execution, and then used to produce control pulses during execution. Besides
their prohibitive cost and limited scalability, such instruments suffer from
poor programmability due to the absence of an instruction set architecture
(ISA). Limited memory for pulse storage ultimately determines the total number
of supported quantum operations. In this work, we present a scalable qubit
control system that enables efficient qubit control using a flexible ISA to
drive a direct digital synthesis (DDS) pipeline producing nanosecond-accurate
qubit control signals dynamically. The designed qubit controller provides a
higher density of control channels, a scalable design, better programmability,
and lower cost compared to state-of-the-art systems. In this work, we discuss
the new qubit controller's capabilities, its architecture and instruction set,
and present experimental results for coherent qubit control.
