- ...in which it has yet to been applied.
- ...in which it has yet to be applied.
Although the first one sounds a little awkward, my hunch is that it's correct because it works when you remove the yet to.
This question is too basic; it can be definitively and permanently answered by a single link to a standard internet reference source designed specifically to find that type of information. See the FAQ for guidance on how to improve it.
Been is a past participle verb form of the verb be, and it's usually incorrect to use a past participle directly after the preposition to.
In fact, to been is just a distorted form of the very common infinitive to be and hence is incorrect.
If you are using the future tense "in which it has yet..." you would not combine it with the past tense "been", at least not without first declaring the switch: "in which it has yet to have been applied".
"In which it has yet to be applied" is the preferred and common usage. The first usage is correct if you add 'have' after the 'to'.