update changelog for release

docs/changelog.md

@@ -3,7 +3,7 @@
 Release notes for `quimb`.
 
 (whats-new-1-9-0)=
-## v1.9.0 (unreleased)
+## v1.9.0 (2024-11-19)
 
 **Breaking Changes**
 
@@ -24,6 +24,7 @@ Release notes for `quimb`.
 - specialize [`CircuitMPS.local_expectation`](quimb.tensor.circuit.CircuitMPS.local_expectation) to make use of the MPS form.
 - add [`PEPS.product_state`](quimb.tensor.tensor_2d.PEPS.product_state) for constructing a PEPS representing a product state.
 - add [`PEPS.vacuum`](quimb.tensor.tensor_2d.PEPS.vacuum) for constructing a PEPS representing the vacuum state $|000\ldots0\rangle$.
+- add [`PEPS.zeros`](quimb.tensor.tensor_2d.PEPS.zeros) for constructing a PEPS whose entries are all zero.
 - [`tn.gauge_all_simple`](quimb.tensor.tensor_core.TensorNetwork.gauge_all_simple): improve scheduling and add `damping` and `touched_tids` options.
 - [`qtn.SimpleUpdateGen`](quimb.tensor.tensor_arbgeom_tebd.SimpleUpdateGen): add gauge difference update checking and `tol` and `equilibrate` settings. Update `.plot()` method. Default to a small `cutoff`.
 - add [`psi.sample_configuration_cluster`](quimb.tensor.tensor_arbgeom.TensorNetworkGenVector.sample_configuration_cluster) for sampling a tensor network using the simple update or cluster style environment approximation.