Identifying users based on smartphone data (Google)
Even I was unable to find a paper on sucha topic by Google. But, I can discuss some features which Google might be using to uniquely identify its users based on smartphone data.


Fingerprint scanning: One of the preliminary methods of scanning users as the fingerprint is unique to every individual. Also, most devices are now equipped with a fingerprint scanner.
Home location: The Google account also keeps a track of the user's home location which can't be directly used to identify a user, but could be an important feature.
Data Personalization: Suppose a user has habit of viewing videos, blogs and websites related with the top tag "artificial intellgence". This personalized information could be used to track down a user.



  Data persoanlization could be applied to apps, videos and websites with which the user interacts. This data will be super complex and probably unique to each individual.



Device Usage: Every individual likes to personalize and use his/her device in their own way. Android 9 had this feature of tracking apps which are most used by the user and also at which times. This is another great factor for identification.
Preliminary device details: IP address, the device's model, Android version, account password are also stored with the Google account.


The above features could be brought together to uniquely identify users as they provide information in different dimensions regarding the user.

The weaker features ( Data personalization, device usage ) can be used with the powerful features ( IP address, passwords ) to uniquely identify a particular user.

All the above information was not mentioned in any paper.

Hope this helps. :-)