DARPA anticipates soliciting innovative proposals towards the realization of heterogeneous quantum computing architectures. Proposed research would investigate innovative approaches that enable revolutionary advances in theory, devices, and system concepts for quantum interconnects, quantum circuit compilers, distributed algorithms, resource estimation, quantum memory/repeater devices, quantum frequency converters, microwave-to-optical transducers, and other elements at the interface of the quantum computing hardware/software stack. Specifically excluded is research that primarily results in evolutionary improvements to the existing state of practice. See Future Program Details section below. DARPA welcomes feedback on the HARQ program goals, metrics, and scope outlined in Future Program Details section below. Feedback should be emailed to HARQ@darpa.mil no later than July 30, 2025, at 5:00 p.m. ET, after which time DARPA will post the final PS. DARPA will host a virtual Proposers Day in support of DARPA Program Solicitation (PS) DARPA-PS-25-31 for HARQ on August 8, 2025, via webcast from 11:00 a.m. to 4:00 p.m. ET. DARPA anticipates releasing DARPA-PS-25-31 prior to Proposers Day. See Proposers Day Details section below for additional registration and meeting details.