From 63e1bd7a4ca37252756faefc35c5f4118ddb3195 Mon Sep 17 00:00:00 2001
From: Johnnie Gray <johnniemcgray@gmail.com>
Date: Mon, 21 Oct 2024 18:59:11 -0700
Subject: [PATCH] add PEPS.zeros

---
 quimb/tensor/tensor_2d.py           | 34 +++++++++++++++++++++++++++++
 tests/test_tensor/test_tensor_2d.py |  6 +++++
 2 files changed, 40 insertions(+)

diff --git a/quimb/tensor/tensor_2d.py b/quimb/tensor/tensor_2d.py
index 2201bf29..1d501e17 100644
--- a/quimb/tensor/tensor_2d.py
+++ b/quimb/tensor/tensor_2d.py
@@ -5008,6 +5008,40 @@ def ones(cls, Lx, Ly, bond_dim, phys_dim=2, like="numpy", **peps_opts):
             **peps_opts,
         )
 
+    @classmethod
+    def zeros(cls, Lx, Ly, bond_dim, phys_dim=2, like="numpy", **peps_opts):
+        """Create a 2D PEPS whose tensors are filled with zeros.
+
+        Parameters
+        ----------
+        Lx : int
+            The number of rows.
+        Ly : int
+            The number of columns.
+        bond_dim : int
+            The bond dimension.
+        physical : int, optional
+            The physical index dimension.
+        peps_opts
+            Supplied to :class:`~quimb.tensor.tensor_2d.PEPS`.
+
+        Returns
+        -------
+        psi : PEPS
+
+        See Also
+        --------
+        PEPS.from_fill_fn
+        """
+        return cls.from_fill_fn(
+            lambda shape: ar.do("zeros", shape, like=like),
+            Lx,
+            Ly,
+            bond_dim,
+            phys_dim,
+            **peps_opts,
+        )
+
     @classmethod
     def rand(
         cls,
diff --git a/tests/test_tensor/test_tensor_2d.py b/tests/test_tensor/test_tensor_2d.py
index 4c6a6ac7..0bd896b8 100644
--- a/tests/test_tensor/test_tensor_2d.py
+++ b/tests/test_tensor/test_tensor_2d.py
@@ -53,6 +53,12 @@ def test_cyclic_edge_cases(self):
         assert peps.is_cyclic_y()
         assert peps.num_indices == peps.num_tensors * 3
 
+    def test_zeros(self):
+        peps = qtn.PEPS.zeros(3, 3, cyclic=True, bond_dim=1)
+        assert peps.num_tensors == 9
+        assert peps.num_indices == 27
+        assert_allclose(peps.to_dense(), np.zeros([512, 1]))
+
     def test_flatten(self):
         psi = qtn.PEPS.rand(3, 5, 3, seed=42)
         norm = psi.H & psi