That's state representation in a quantum circuit diagram (eg similar to gates etc). The motivation to pick a triangle is to have similar icons/pictures like quantum processes/diagrammatic approach. The state's Dirac notation is also shown inside that gray triangle.
The Dirac notation can be also obtained as TraditionalForm of a quantum state. Look at this notebook for more details:
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Thank you! I missed the little ket inside the triangle pointing the opposite way. Forgive me.
yes, they are the same things in Wolfram quantum framework. Where you are referring to in this notebook (with potential mistake)?
Aren't the <x| forms usually called the "bras" and the |x> forms the "kets?" Or do you have them swapped on purpose?
