Hello Ghalia,
You are right, the conventions may vary between the course and exercises, and it wasn't clearly specified in the Homework. We kept that in mind while correcting exercises 1 and 2.
The important point is that, whatever convention you chose, it stays consistent throughout the exercise. For instance for the teleportation, the appropriate operator I, X, Z, iY has to be applied depending on your convention so as to get back the same extra-state (or possibly the same with a phase change).
We will be extra-careful and give correctly the Bell basis in the exam ;)
Antoine
(PS: There was in fact a discussion earlier - but in french - about this issue https://moodlearchive.epfl.ch/2022-2023/mod/forum/discuss.php?d=82787 )
