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