For those who don't know Quantum Paper is the rumoured new user interface which most likely will be seen in the upcoming version Android and on other platforms, for more information head over to Android Police. Additionally the newest leak of the Android 'L' release has shown that status bar will not have the gradient shade behind it, therefore all the concepts have been updated to match it.
Using the known information I decided to put together a few concepts for Apps based on the Quantum Paper design.
Google Play Store
Google Play Music
Keep in mind the Quantum Paper versions of these apps don't exist (at least yet), this is just a concept. However there is a guide thread on how to make your app have the Quantum Paper like UI.