First you have to decide which Quality Center API you like to use. The REST API or the OTA API. Using REST you can use nearly any language you want. Using the OTA API you need a language which supports COM objects. The examples in the OTA API documentation use VB. Personally I prefer Ruby to access Quality Center via the OTA API. Here is an example of how to connect to Quality Center and retrieve open bugs:
require 'win32ole'
tdc = WIN32OLE.new('TDApiOle80.TDConnection')
tdc.InitConnectionEx('https://yourserver/qcbin/')
tdc.Login('user', 'pass')
tdc.Connect('domain', 'project')
bug_factory = tdc.BugFactory
bug_filter = bug_factory.Filter
bug_filter["BG_STATUS"] = 'Open'
bugs = bug_factory.NewList(bug_filter)
You can also connect to Oracle using Ruby, see this question.