Changing the path of jQuery to use a CDN instead of the local file system
Add the following code in the template.php file of your theme. (Replace mytheme with the actual short name of your theme.)

function mytheme_js_alter(&amp;$javascript) {
  $javascript['misc/jquery.js']['type'] = 'external';
  $javascript['misc/jquery.js']['data'] = 'http://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js';
}


As you are replacing the copy of the jQuery library with the same version copy hosted on Google, it doesn't make much sense to do it for just a theme. It would make sense to change it independently from the theme used from Drupal.   

If you plan to use a different version of the library, you should first check there aren't incompatibilities with the jQuery version, and JavaScript code used from Drupal, or third-party modules. In case of incompatibilities, some JavaScript files used by Drupal could need to be replaced (using hook_js_alter()). That is what the jQuery Update module does.