MIMO: Multilingual Information Retrieval via Monolingual Objectives

Youngjoon Jang, Seongtae Hong, Heuiseok Lim


Abstract
Multilingual Information Retrieval (MLIR) reflects real-world search environments in which queries and relevant documents may appear in different languages within a mixed-language corpus. However, existing embedding models are primarily optimized for Multi-Monolingual retrieval and their performance often degrades substantially in MLIR settings. Moreover, directly applying conventional contrastive learning to MLIR can exacerbate language clustering and expose a trade-off between cross-lingual alignment and embedding uniformity. To address these limitations, we propose MIMO: Multilingual Information Retrieval via Monolingual Objectives, a two-stage framework that uses a stable English semantic space as an anchor. MIMO first initializes cross-lingual alignment through knowledge distillation, and then jointly optimizes distillation and cross-lingual contrastive learning to improve retrieval discrimination while preserving alignment. Extensive experiments show that MIMO consistently outperforms existing cross-lingual training baselines across various MLIR and Multi-Monolingual benchmarks. MIMO also remains competitive with off-the-shelf models of similar or larger parameter scales. Furthermore, our cross-lingual Alignment-Uniformity analysis clarifies the distinct roles of the two loss components and shows that their combination yields a favorable trade-off between alignment and uniformity.
Anthology ID:
2026.emnlp-main.156
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
3597–3612
Language:
URL:
https://aclanthology.org/2026.emnlp-main.156/
DOI:
Bibkey:
Cite (ACL):
Youngjoon Jang, Seongtae Hong, and Heuiseok Lim. 2026. MIMO: Multilingual Information Retrieval via Monolingual Objectives. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 3597–3612, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MIMO: Multilingual Information Retrieval via Monolingual Objectives (Jang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.156.pdf