It's interesting to see how this feature works, especially when you consider Google's claim that pages load in less than 0.1 seconds. Like a magician, Google uses tricks to make people think that pages load faster than they really do.
All the Wikipedia results with a blue "Quick View" button have special sections in Google's source code that include the first part of the articles. When you tap the "Quick View" result, the article appears to load instantly, but you only see the first paragraphs, which are included in Google's code, just like snippets. Google loads in the background the rest of the article: it's a simplified version of the mobile Wikipedia article from the Google Cache. An example of page that includes the second part of a Wikipedia article: http://websearch-experiments.googleusercontent.com/B/08/d88ede51537960e3_926bb07ecb8a2bc1.htm.
Here's what happens if Google can't load the rest of the article: you get the error message "Error loading the entire article. Try again".
But is Quick View really fast? I've loaded the Wikipedia article about lettuce in the desktop Chrome and changed the user-agent to Galaxy Nexus/Android 4.0.2. Here are the load times obtained from Chrome's developer tools (I've only included the results for the main HTML file, the images are loaded from Wikipedia's site even when you use Quick View).
- Quick View: 120 ms
- Regular Wikipedia article: 522 ms
I've tested many other articles and Quick View pages consistently loaded in 100-130 milliseconds, while the original Wikipedia articles loaded about 4 times slower. It's a significant difference, especially if you use a slow mobile Internet connection with high latency.
Here's the total loading time for the page and its resources:
- QuickView: 30 requests, 143 KB transferred, 986ms total loading time
- Wikipedia: 36 requests, 296 KB transferred, 1.68 s total loading time