Perhaps you should try some spelling variations:
"quantum classical" » "quantum chemical"
"quantum physical" » "quantum chemical", "quantum critical", "quantum logical"
"quantum optical" » "quantum optics", "quantum chemical"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((((("quantum physical") OR ("quantum physics"))) OR ("quantum optical"))) OR ("quantum classical")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((\"quantum physical\") OR (\"quantum physics\"))) or (\"quantum optical\"))) or (\"quantum classical\"))".
• Removing quotes may allow a broader search: (((((( quantum physical ) OR ( quantum physics ))) or ( quantum optical ))) or ( quantum classical )).
• Adding a wildcard symbol may retrieve word variants: (((((("quantum physical") OR ("quantum physics"))) or ("quantum optical"))) or ("quantum classical"))*.