Bottleneck Tokens for Unified Multimodal Retrieval. - Siyu Sun; Jing Ren; Zhaohe Liao; Dongxiao Mao; Xiangyuan Ren; Yiyi Zhang 002; Haohua Zhao 001; Weixiong Lin; Jiang Shaohua; Liqing Zhang 001; Yuchao Zheng (CoRR, 2026)