Vitalik Buterin: Fiat digital currencies could interact with crypto  

Basically, if you can prove to the ethereum chain that you made a transaction inside a CBDC system, you can use that to build an automated smart contract dex,” Buterin told Decrypt. Smart contracts are automated pieces of code that run on the Ethereum blockchain and a DEX is a decentralized exchange, where cryptocurrencies are traded between people without a central bank or third party involved.

https://decrypt.co/18420/vitalik-buterin-fiat-digital-currencies-could-interact-with-crypto