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

Quantum Computing (QC) is an emerging research field that is attracting significant interest from the scientific community due to its potential to solve complex problems more efficiently than traditional computers by leveraging the principles of quantum physics. Even though real quantum computers exist, at the moment we are still in the early stages of development of these innovative technologies, and many of their capabilities and limitations are yet to be discovered. In this work, we present an overview of the second edition of QuantumCLEF, a lab that focuses on the application of Quantum Annealing (QA), a specific QC paradigm, for different tasks related to IR and RS. The main objective of the QuantumCLEF lab is to investigate QC, raise awareness, and develop and evaluate new QC algorithms for different applications. This lab represents a great chance for researchers and industry practitioners to understand more about this new field by having access to real quantum computers, which are still not easily accessible nowadays. This edition consisted of three different tasks: Feature Selection for IR and RS systems, Instance Selection for IR systems, and Clustering for IR systems. There have been a total of 44 teams that registered for this lab, and eventually, 5 teams managed to successfully submit their runs following the lab guidelines. Participants have been provided with examples, tutorials, and comprehensive materials due to the novelty of the QC field, allowing them to understand how QA works and how to program quantum annealers.