Figure 6: Tensor network costs scale polynomially in
d at fixed accuracy. Best-cell trajectory of the TDVP V-step variants (minimum mean sliced Wasserstein over the hyperparameter search box, analytic
Vt ) relative to the Dense-grid baseline across
d∈{2,…,8} ; the underlying data are the same runs that produce Table 1 . (a) Compression ratio
R=Nd/(2Nχ+(d−2)Nχ2) , the Dense-grid amplitude count over the MPS parameter count at the achieved bond dimension
χ ;
R rises by roughly an order of magnitude per added
d , reaching
∼107 at
d=8 . The shaded band in all three panels marks the regime where the Dense-grid baseline is feasible and was run (
d≤5 ); every tensor network marker is a measured run. (b) Evolution acceleration factor
S=tDense-grid/tMPS , the Dense-grid evolution wall-clock time over the tensor network’s, so that values above unity mean the tensor network is faster. The wall-clock time is summed per Trotter step and excludes the per-step metric callback; that callback is under
3% of the enclosing loop at
d≥4 but over
90% at
d=2 , enough to invert the apparent ordering of
d=2 and
d=3 if included. TCI+1TDVP crosses above unity near
d=4 and TCI+2TDVP near
d=5 , after which the tensor network methods are cheaper than Dense-grid at matching accuracy, the one exception being TCI+2TDVP at
d=6 (
0.9× ). The Dense-grid numerator is measured at
d∈{3,4,5} and is a log-linear fit through those three points elsewhere, the
Nd grid being infeasible above
d=5 ; the
d=6 exception falls in the projected regime. The tensor network denominators are measured from runs at each shown
d . (c) Best-cell accuracy
SW(ΨT) (sliced Wasserstein of the endpoint state) versus
d : TCI+1TDVP and TCI+2TDVP stay within a factor of
1.7 of the target–target reference across the full range, without upward drift in
d , and track the Dense-grid baseline wherever it is feasible. The cost–accuracy Pareto frontiers are given in the supplement (Supplementary Section S2 , Figure S1 ); a replicated
n=10 audit with a second metric appears in Supplementary Section S2.2 .