Is there a 64 bit quicktime version for windows 10? All the descriptions that I have found on-line don't state either 32 or 64bit.
No. The only download for the current version of quicktime (7.7.8) is this one: https://support.apple.com/kb/DL837?viewlocale=en_GB&locale=en_GB
It's 32-bit. There are no 64-bit options.
There is no 64-bit version of QuickTime, primarily because Apple has ceased development of QuickTime on Windows (except for security and minor updates, presumably). QuickTime has been 7.x for 10 years now, and 8.0 does not seem to be anywhere in the distance.
If you need a codec for QuickTime videos (and more), you would be better off installing K-Lite Codec Pack.