Swift Homomorphic Encryption implements the Brakerski-Fan-Vercauteren (BFV) HE scheme (https://eprint.iacr.org/2012/078, https://eprint.iacr.org/2012/144) (without bootstrapping). This is a leveled HE scheme, which supports a limited number of encrypted adds and multiplies (among other operations).

[Disclosure: I work on the team responsible for the feature]