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

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 classical") OR ("quantum optical"))) OR ("quantum physics")).
• Removing quotes may allow a broader search: (((( quantum classical ) or ( quantum optical ))) or ( quantum physics )).
• Adding a wildcard symbol may retrieve word variants: (((("quantum classical") or ("quantum optical"))) or ("quantum physics"))*.