It's possible to define a map in QML like this

property variant theMap: { "key1":"value1", "key2":"value2", "key3":"value3" }

and access the values like this

theMap["key1"]

which returns "value1" as expected.

But this type is not listed here
http://doc.qt.nokia.com/4.7-snapshot/qdeclarativebasictypes.html