What is the Cross-Rollup DEX That Vitalik Mentioned?

While people are still thinking about using rollups to alleviate Layer 1 congestion, Vitalik is already considering how to enable interaction between rollups. Six days ago, Vitalik proposed a concept called "cross-rollup DEX," which mentioned that when one rollup has smart contract deployment and another rollup doesn't have full smart contract functionality, assets can be transferred between the two rollups in a decentralized manner. It has a feeling of "remote teleportation."