Modern experiments in particle physics, astroparticle physics, and cosmology increasingly rely on large cryogenic sensor arrays to achieve the sensitivity needed to probe phenomena beyond the Standard Model, including the neutrino-mass scale, dark-matter interactions, neutrinoless double-beta decay, and B-mode polarization of the cosmic microwave background. These efforts require the simultaneous readout of tens to hundreds of thousands of detectors, pushing current data-acquisition technologies and motivating the use of frequency-division multiplexing, particularly microwave SQUID multiplexing (𝜇MUX), to scale to such array sizes. In this work we present the Quantum Interface Controller (QIC), a modular software-defined radio platform for high-fidelity, scalable readout of cryogenic detectors and superconducting qubits. Based on Xilinx Zynq UltraScale+ MPSoC and RFSoC technology, the QIC integrates multi-gigahertz DACs/ADCs, FPGA-based real-time processing, and a unified software stack, supporting both DirectRF generation and super-heterodyne sampling to synthesize and demodulate thousands of microwave tones per unit. A firmware-integrated Cryogenic Detector Emulator (CryoDE) provides a digital detector twin for hardware-in-the-loop validation. This paper presents the QIC architecture, firmware and software environment, it is currently being utilized in the ECHo neutrino-mass experiment, the BULLKID-DM dark-matter search, and for superconducting-qubit readout in quantum-computing applications, demonstrating its suitability as a scalable platform for next-generation quantum-sensor arrays.