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 physics") OR ((("quantum physical") OR ("quantum classical"))))) OR ("quantum optical")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"quantum physics\") or (((\"quantum physical\") OR (\"quantum classical\"))))) or (\"quantum optical\"))".
• Removing quotes may allow a broader search: (((( quantum physics ) or ((( quantum physical ) OR ( quantum classical ))))) or ( quantum optical )).
• Adding a wildcard symbol may retrieve word variants: (((("quantum physics") or ((("quantum physical") OR ("quantum classical"))))) or ("quantum optical"))*.