PhD in the wrong department? I studied physics for my undergraduate and master's and I've been offered a position in the computing department for my PhD in the UK. The topic is quantum information (hence, the overlap with computing does make sense) and there is no coursework. I'm very happy with the offer and my supervisor. The only problem is that I am a bit nervous about being in the "wrong" department, given my background. 

I see myself as a physics student and I can't really picture calling myself a computer scientist. I'm much more comfortable talking about, say, condensed matter than algorithms and data structures. I'm more interested and would probably get more out of a physics department talk than a CS talk. 

Should I request a change of department but with the same supervisor before I begin? Alternatively, could I just hang around more at the physics department instead and not care about the official affiliation? Or is this a non-issue that I'm needlessly worried about? In case it matters, my funding is from a university level scholarship, not a departmental one. 

Related but different question: Problem of mentioning the department affiliated with PhD degrees
Investigate with your potential advisor, director of graduate studies, or chair (in this order, for ease of everybody's life) the possibility of getting a co-advisor from the physics department, provided there is someone with an expertise on the topic. You may even look beyond your institution, but that would require some serious argument.

One of the comments to the question mentioned the issue of "labels" of degree. 
I don't see it being an issue for industry jobs. Many companies routinely hire physicists and computer scientists alike, and ask them to do similar jobs. 
If you want to get a faculty position in a physics department, then perhaps you may have an issue if you have a CS degree, but you may be able to play the game by publishing in both CS and physics venue.