QuantumCLEF 2025: Overview of the Second Quantum Computing Challenge for Information Retrieval and Recommender Systems at CLEF

The emerging field of Quantum Computing (QC) is attracting considerable research interest due to its potential. It is in fact believed that QC could revolutionize the way we approach complex problems by significantly reducing the time required to solve them. Although QC is still in its early stages of development, certain problems can already be addressed using quantum computers, offering a glimpse into its capabilities. The goal of the QuantumCLEF lab is to raise awareness of QC and to design, develop, and evaluate new QC algorithms aimed at solving challenges typically encountered in the implementation of Information Retrieval (IR) and Recommender Systems (RS). Furthermore, the lab provides a valuable opportunity to engage with QC technologies, which are often difficult to access. In this work, we present an overview of the second edition of QuantumCLEF, a lab focused on applying Quantum Annealing (QA), a specific QC paradigm, to three tasks: Feature Selection for IR and RS systems, Instance Selection for IR systems, and Clustering for IR systems. A total of 44 teams registered for the lab, with 5 teams successfully submitting their runs in accordance with the lab guidelines. Given the novelty of the topics, participants were provided with extensive examples and comprehensive materials to help them understand how QA works and how to program quantum annealers.