Just to clarify for future readers: Alpha products are usually not available to the general public as they are in an early testing phase and usually require specific agreements with Google, for testing specific features, and are often directly supported by the engineering team building the feature. I say "usually" because there are sometimes a few features made available publicly in Alpha.
If you have not been contacted about an Alpha program by a Google employee, you probably won't have access. Once invited to an Alpha, it is true that API access is controlled through the "whitelisting" mechanism described earlier.