Manuscript Oai265-A@2 · Oai265-A.tex · section · c0a34a45
The separate algorithmic interface
Stage 3: PEPS existence, algorithms, and approximation budgets › The separate algorithmic interface · lines 910–929
An algorithmic theorem must fix at least:
finite encodings and bit lengths for the local matrices;
the gap and uniqueness promises and how they are supplied;
the accuracy, normalization, and global phase convention;
output tensor dimensions and entry precision;
running time and success probability;
which contraction, normalization, or verification tasks are included.
Existence of tensors with arbitrary real entries does not itself bound their bit complexity or give a method to find them.
Generic PEPS contraction has strong complexity obstructions SchuchEtAl. Those generic results do not, without a promise-preserving reduction, prove hardness of the particular unique, uniformly gapped ground-state class frozen here.