Quantum computing experts tend to say that DWave is not a "true" universal quantum computer which uses the quantum version of logic gates, rather it combines quantum physics with what's known as an "adiabatic computer", which does let it do certain types of calculations better than a classical computer though it's not clear whether this can be scaled up (see the Scientific American article [here][1] for a good summary). 

As for your question, I tried searching "quantum computer" on google books, then when the list of results came up I clicked "search tools" at the top, then switched from "any time" to "custom range", and restricted the date range in various ways to try to find the earliest example of a sci-fi book with this phrase. Earliest I could find were the snippets [here][2] that showed up on pp. 155-159 of an issue of "Analog Science Fiction & Fact", a little searching for more snippets from the same story showed that it's the novelette "A Gift Before Leaving" by W.R. Thompson, from the [Mid-December 1992 issue][3] (see the two consecutive snippets on p. 159 [here][4] and [here][5]). That issue is [available cheap][6] from marketplace sellers on amazon, if you want to read it. Of course google books doesn't include all publications, but this is probably *one* of the earliest, anyway.


  [1]: http://www.scientificamerican.com/article/d-waves-quantum-computer-courts-controversy/
  [2]: http://books.google.com/books?id=7KE6AQAAIAAJ&focus=searchwithinvolume&q=quantum%20computer
  [3]: http://www.isfdb.org/cgi-bin/pl.cgi?56989
  [4]: http://books.google.com/books?id=7KE6AQAAIAAJ&focus=searchwithinvolume&q=ketamines
  [5]: http://books.google.com/books?id=7KE6AQAAIAAJ&focus=searchwithinvolume&q=%22involving%20bright%20lights%22
  [6]: http://www.amazon.com/Analog-Science-Fiction-Fact-Mid-December/dp/B000P21F3E