If you are site owner, you can easily remove site from google (even from google cache). I have removed our one of beta testing (which duplicates with live site) using Google Webmaster tool. Process is shown in image below:
- Login in Google Webmaster Tool.
- Add your site in Google Webmaster Tool.
- Go to Site Configuration
- Click Crawler Access
- Click on URL removal tool.
- Submit your URL. Google will remove your from index within 24hrs.