Could pulsar timing arrays see primordial gravity waves?

[windy miller]

Im wondering if pulsar arrays could see primordial gravity waves?
I have understood the only way to seem them would be to
a) via indirect imprint on CMB polarisation
b) direct viewing via some gigantic space based interferometer like Big Bang Observer
However I was looking at this image: https://upload.wikimedia.org/wikipe..._astrophysical_gravitational-wave_sources.png
and it seems to imply pulsar timing array projects like EPTA and IPTa might have a shot at it. Have I misunderstood this or is this a genuine possibility?

 

[Chalnoth]

It's potentially possible, but nobody yet knows what the level of primordial gravity waves is. They could be a lot smaller than would be required to detect them this way.