You can't using this code on its own. You do have two options, though:
1) Wrap your code in a wrapper somewhere (essentially abstracting away this call), which does a cache check first, and runs these queries if the cached item does not exist or is expired.
2) Extend the Auth library, specifically its EloquentUserProvider class, and modify the query performed by the retrieveById()
method.
You can see one method of abstracting methods and caching in Chris Fidao's Implementing Laravel. The accompanying book is handy!