netket.models.tensor_networks.MPSOpen

class netket.models.tensor_networks.MPSOpen

Bases: Module

An open Matrix Product State (MPS) for a quantum state of discrete degrees of freedom. The MPS is defined as

\[\Psi(s_1,\dots s_N) = \mathrm{Tr} \left[ A[s_1]\dots A[s_N] \right] ,\]

for arbitrary local quantum numbers \(s_i\), where \(A[s_{i}]\) are vectors of shape \((\text{bond_dim},)\) for \(i=1,N\) and matrices of shape \((\text{bond_dim}, \text{bond_dim})\) for \(i=2, \dots N-1\) , depending on the value of the local quantum number \(s_i\).

Attributes

checkpoint: bool = True

Whether to use jax.checkpoint on the scan function for memory efficiency.

unroll: int = 1

the number of scan iterations to unroll within a single iteration of a loop.

hilbert: HomogeneousHilbert

Hilbert space on which the state is defined.

bond_dim: int

Bond dimension of the MPS tensors. See formula above.

kernel_init: Callable[[Any, Sequence[int], Any], Union[ndarray, Array]]

the initializer for the MPS weights. This is added to an identity tensor.

Methods

__call__(x)

Queries the tensor network for the input configurations x.

Parameters:

x – the input configuration

contract_mps(qn)

Internal function, used to contract the tensor network with some input tensor.

Parameters:

qn – The input tensor to be contracted with this MPS