Bad Qubits — Learn Quantum by Doing

Multiple choice

A PEPS stores a 2D state with only O(n d D^4) parameters (polynomial in the number of sites). According to the lesson, what is the hard part for a general PEPS?

Writing down the tensors, which requires an exponential number of SVDs
Exact contraction — even computing one amplitude or the norm is #P-hard
Adding a single physical index per site, which is intractable
Storing the tensors, which requires exponential memory