Privacy on Ethereum is being actively worked on by a number of different teams.
There are a couple of key technologies to know about:
- Zero Knowledge-based
- zk-SNARKs (used in Zcash)
Aztec Protocol is building an efficient zero-knowledge privacy protocol and decentralised exchange. The protocol is already live on Ethereum's mainnet.
Starkware Industries is using STARK technology to improve scalability and privacy on Ethereum.