  Quantum circuits utilizing real time feedback techniques (such as active
reset and mid-circuit measurement) are a powerful tool for NISQ-era quantum
computing. Such techniques are crucial for implementing error correction
protocols, and can reduce the resource requirements of certain quantum
algorithms. Realizing these capabilities requires flexible, low-latency
classical control. We have developed a custom FPGA-based processor architecture
for QubiC, an open source platform for superconducting qubit control. Our
architecture is distributed in nature, and consists of a bank of lightweight
cores, each configured to control a small (1-3) number of signal generator
channels. Each core is capable of executing parameterized control and readout
pulses, as well as performing arbitrary control flow based on mid-circuit
measurement results. We have also developed a modular compiler stack and
domain-specific intermediate representation for programming the processor. Our
representation allows users to specify circuits using both gate and pulse-level
abstractions, and includes high-level control flow constructs (e.g. if-else
blocks and loops). The compiler stack is designed to integrate with quantum
software tools and programming languages, such as TrueQ, pyGSTi, and OpenQASM3.
In this work, we will detail the design of both the processor and compiler
stack, and demonstrate its capabilities with a quantum state teleportation
experiment using transmon qubits at the LBNL Advanced Quantum Testbed.
