Ancestry.com picked up the 1940 census images (on a BIG hard drive) at 12:01 am this morning, April 2nd, and then immediately started to load the images, "on the fly" onto their servers. All images should be up within a week.
The 1940 images were made public today after a 72 year mandated confidentiality period. The NARA site, which is experienced unexpected user pressure (over 22 million hits by 10 am today although the website expected a maximum of 10 million per day) opened up those images to the public today as well.
FamilySearch will also put the 1940 images on their website, and will some other companies.
Thus it's not clear what your question is. Name indexes could not start until the 1940 census became public, and a full name index is going to take from 6 months to ??? to complete by the various parties. If you want to search the 1940 census now, you will need to search by location of your family translated into enumeration districts.
If you are not familiar with locational searches, use our tutorial on the matter for the 1940 census: http://www.stevemorse.org/census/quiz.php and use our unified tool to find the enumeration district number for a location in 1940: http://www.stevemorse.org/census/unified.html