Quimb

**Breaking Changes**

- all singular value renormalization is turned off by default
- [`TensorNetwork.compress_all`](quimb.tensor.TensorNetwork.compress_all)
now defaults to using some local gauging


**Enhancements:**

- add `quimb.tensor.tensor_1d_compress.py` with functions for compressing generic
1D tensor networks (with arbitrary local structure) using various methods.
The methods are:

- The **'direct'** method: [`tensor_network_1d_compress_direct`](quimb.tensor.tensor_1d_compress.tensor_network_1d_compress_direct)
- The **'dm'** (density matrix) method: [`tensor_network_1d_compress_dm`](quimb.tensor.tensor_1d_compress.tensor_network_1d_compress_dm)
- The **'zipup'** method: [`tensor_network_1d_compress_zipup`](quimb.tensor.tensor_1d_compress.tensor_network_1d_compress_zipup)
- The **'zipup-first'** method: [`tensor_network_1d_compress_zipup_first`](quimb.tensor.tensor_1d_compress.tensor_network_1d_compress_zipup_first)
- The 1 and 2 site **'fit'** or sweeping method: [`tensor_network_1d_compress_fit`](quimb.tensor.tensor_1d_compress.tensor_network_1d_compress_fit)
- ... and some more niche methods for debugging and testing.

And can be accessed via the unified function [`tensor_network_1d_compress`](quimb.tensor.tensor_1d_compress.tensor_network_1d_compress).
Boundary contraction in 2D can now utilize any of these methods.
- add `quimb.tensor.tensor_arbgeom_compress.py` with functions for compressing
arbitrary geometry tensor networks using various methods. The methods are:

- The **'local-early'** method:
[`tensor_network_ag_compress_local_early`](quimb.tensor.tensor_arbgeom_compress.tensor_network_ag_compress_local_early)
- The **'local-late'** method:
[`tensor_network_ag_compress_local_late`](quimb.tensor.tensor_arbgeom_compress.tensor_network_ag_compress_local_late)
- The **'projector'** method:
[`tensor_network_ag_compress_projector`](quimb.tensor.tensor_arbgeom_compress.tensor_network_ag_compress_projector)
- The **'superorthogonal'** method:
[`tensor_network_ag_compress_superorthogonal`](quimb.tensor.tensor_arbgeom_compress.tensor_network_ag_compress_superorthogonal)
- The **'l2bp'** method:
[`tensor_network_ag_compress_l2bp`](quimb.tensor.tensor_arbgeom_compress.tensor_network_ag_compress_l2bp)

And can be accessed via the unified function
[`tensor_network_ag_compress`](quimb.tensor.tensor_arbgeom_compress.tensor_network_ag_compress).
1D compression can also fall back to these methods.
- support PBC in
[`tn2d.contract_hotrg`](quimb.tensor.tensor_2d.TensorNetwork2D.contract_hotrg),
[`tn2d.contract_ctmrg`](quimb.tensor.tensor_2d.TensorNetwork2D.contract_ctmrg),
[`tn3d.contract_hotrg`](quimb.tensor.tensor_3d.TensorNetwork3D.contract_hotrg) and
the new function
[`tn3d.contract_ctmrg`](quimb.tensor.tensor_3d.TensorNetwork3D.contract_ctmrg).
- support PBC in
[`gen_2d_bonds`](quimb.tensor.tensor_2d.gen_2d_bonds) and
[`gen_3d_bonds`](quimb.tensor.tensor_3d.gen_3d_bonds), with ``cyclic`` kwarg.
- support PBC in
[`TN2D_rand_hidden_loop`](quimb.tensor.tensor_builder.TN2D_rand_hidden_loop)
and
[`TN3D_rand_hidden_loop`](quimb.tensor.tensor_builder.TN3D_rand_hidden_loop),
with ``cyclic`` kwarg.
- support PBC in the various base PEPS and PEPO construction methods.
- add [`tensor_network_apply_op_op`](quimb.tensor.tensor_arbgeom.tensor_network_apply_op_op)
for applying 'operator' TNs to 'operator' TNs.
- tweak [`tensor_network_apply_op_vec`](quimb.tensor.tensor_arbgeom.tensor_network_apply_op_vec)
for applying 'operator' TNs to 'vector' or 'state' TNs.
- add [`tnvec.gate_with_op_lazy`](quimb.tensor.tensor_arbgeom.TensorNetworkGenVector.gate_with_op_lazy)
method for applying 'operator' TNs to 'vector' or 'state' TNs like $x \rightarrow A x$.
- add [`tnop.gate_upper_with_op_lazy`](quimb.tensor.tensor_arbgeom.TensorNetworkGenOperator.gate_upper_with_op_lazy)
method for applying 'operator' TNs to the upper indices of 'operator' TNs like $B \rightarrow A B$.
- add [`tnop.gate_lower_with_op_lazy`](quimb.tensor.tensor_arbgeom.TensorNetworkGenOperator.gate_lower_with_op_lazy)
method for applying 'operator' TNs to the lower indices of 'operator' TNs like $B \rightarrow B A$.
- add [`tnop.gate_sandwich_with_op_lazy`](quimb.tensor.tensor_arbgeom.TensorNetworkGenOperator.gate_sandwich_with_op_lazy)
method for applying 'operator' TNs to the upper and lower indices of 'operator' TNs like $B \rightarrow A B A^\dagger$.
- unify all TN summing routines into
[`tensor_network_ag_sum](quimb.tensor.tensor_arbgeom.tensor_network_ag_sum),
which allows summing any two tensor networks with matching site tags and
outer indices, replacing specific MPS, MPO, PEPS, PEPO, etc. summing routines.
- add [`rand_symmetric_array`](quimb.tensor.tensor_builder.rand_symmetric_array),
[`rand_tensor_symmetric`](quimb.tensor.tensor_builder.rand_tensor_symmetric)
[`TN2D_rand_symmetric`](quimb.tensor.tensor_builder.TN2D_rand_symmetric)
for generating random symmetric arrays, tensors and 2D tensor networks.

**Bug fixes:**

- fix scipy sparse monkey patch for scipy>=1.13 ({issue}`222`)
- fix autoblock bug where connected sectors were not being merged ({issue}`223`)


---


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**Enhancements:**

- [qu.randn](quimb.randn): support `dist="rademacher"`.
- support `dist` and other `randn` options in various TN builders.

**Bug fixes:**

- restore fallback (to `scipy.linalg.svd` with driver='gesvd') behavior for truncated SVD with numpy backend.


---


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**Enhancements:**

- add `normalized=True` option to [`tensor_network_distance`](quimb.tensor.tensor_core.tensor_network_distance) for computing the normalized distance between tensor networks: $2 |A - B| / (|A| + |B|)$, which is useful for convergence checks. [`Tensor.distance_normalized`](quimb.tensor.tensor_core.Tensor.distance_normalized) and [`TensorNetwork.distance_normalized`](quimb.tensor.tensor_core.TensorNetwork.distance_normalized) added as aliases.
- add [`TensorNetwork.cut_bond`](quimb.tensor.tensor_core.TensorNetwork.cut_bond) for cutting a bond index

**Bug fixes:**

- removed import of deprecated `numba.generated_jit` decorator.


---


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**Enhancements:**

- add [`TensorNetwork.visualize_tensors`](quimb.tensor.drawing.visualize_tensors)
for visualizing the actual data entries of an entire tensor network.
- add [`ham.build_mpo_propagator_trotterized`](quimb.tensor.tensor_1d_tebd.LocalHam1D.build_mpo_propagator_trotterized)
for building a trotterized propagator from a local 1D hamiltonian. This
also includes updates for creating 'empty' tensor networks using
[`TensorNetwork.new`](quimb.tensor.tensor_core.TensorNetwork.new), and
building up gates from empty tensor networks using
[`TensorNetwork.gate_inds_with_tn`](quimb.tensor.tensor_core.TensorNetwork.gate_inds_with_tn).
- add more options to [`Tensor.expand_ind`](quimb.tensor.tensor_core.Tensor.expand_ind)
and [`Tensor.new_ind`](quimb.tensor.tensor_core.Tensor.new_ind): repeat
tiling mode and random padding mode.
- tensor decomposition: make ``eigh_truncated`` backend agnostic.
- [`tensor_compress_bond`](quimb.tensor.tensor_core.tensor_compress_bond): add
`reduced="left"` and `reduced="right"` modes for when the pair of tensors is
already in a canonical form.
- add [`qtn.TN2D_embedded_classical_ising_partition_function`](quimb.tensor.tensor_builder.TN2D_embedded_classical_ising_partition_function) for constructing 2D
(triangular) tensor networks representing all-to-all classical ising
partition functions.

**Bug fixes:**

- fix bug in [`kruas_op`](quimb.kraus_op) when operator spanned multiple
subsystems ({issue}`214`)
- fix bug in [`qr_stabilized`](quimb.tensor.decomp.qr_stabilized) when the
diagonal of `R` has significant imaginary parts.
- fix bug in quantum discord computation when the state was diagonal ({issue}`217`)


---


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**Breaking Changes**

- {class}`~quimb.tensor.Circuit` : remove `target_size` in preparation for
all contraction specifications to be encapsulated at the contract level (e.g.
with `cotengra`)
- some TN drawing options (mainly arrow options) have changed due to the
backend change detailed below.

**Enhancements:**

- [TensorNetwork.draw](quimb.tensor.TensorNetwork.draw): use `quimb.schematic`
for main `backend="matplotlib"` drawing. Enabling:
1. multi tag coloring for single tensors
2. arrows and labels on multi-edges
3. better sizing of tensors using absolute units
4. neater single tensor drawing, in 2D and 3D
* add [quimb.schematic.Drawing](quimb.schematic.Drawing) from experimental
submodule, add example docs at {ref}`schematic`. Add methods `text_between`,
`wedge`, `line_offset` and other tweaks for future use by main TN drawing.
- upgrade all contraction to use `cotengra` as the backend
- [`Circuit`](quimb.tensor.Circuit) : allow any gate to be controlled by any
number of qubits.
- [`Circuit`](quimb.tensor.Circuit) : support for parsing `openqasm2`
specifications now with custom and nested gate definitions etc.
- add [`is_cyclic_x`](quimb.tensor.TensorNetwork2D.is_cyclic_x),
[`is_cyclic_y`](quimb.tensor.TensorNetwork2D.is_cyclic_y) and
[`is_cyclic_z`](quimb.tensor.TensorNetwork3D.is_cyclic_z) to
[TensorNetwork2D](quimb.tensor.TensorNetwork2D) and
[TensorNetwork3D](quimb.tensor.TensorNetwork3D).
- add [TensorNetwork.compress_all_1d](quimb.tensor.TensorNetwork.compress_all_1d)
for compressing generic tensor networks that you promise have a 1D topology,
without casting as a [TensorNetwork1D](quimb.tensor.TensorNetwork1D).
- add [MatrixProductState.from_fill_fn](quimb.tensor.tensor_1d.MatrixProductState.from_fill_fn)
for constructing MPS from a function that fills the tensors.
- add [Tensor.idxmin](quimb.tensor.Tensor.idxmin) and
[Tensor.idxmax](quimb.tensor.Tensor.idxmax) for finding the index of the
minimum/maximum element.
- 2D and 3D classical partition function TN builders: allow output indices.
- [`quimb.experimental.belief_propagation`]([`quimb.experimental.belief_propagation`]):
add various 1-norm/2-norm dense/lazy BP algorithms.

**Bug fixes:**

- fixed bug where an output index could be removed by squeezing when
performing tensor network simplifications.


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**Breaking Changes**

- Quantum circuit RZZ definition corrected (angle changed by -1/2 to match
qiskit).

**Enhancements:**

- add OpenQASM 2.0 parsing support: [`Circuit.from_openqasm2_file`](quimb.tensor.Circuit.from_openqasm2_file),
- [`Circuit`](quimb.tensor.Circuit): add RXX, RYY, CRX, CRY, CRZ, toffoli, fredkin, givens gates
- truncate TN pretty html reprentation to 100 tensors for performance
- add [`Tensor.sum_reduce`](quimb.tensor.Tensor.sum_reduce) and [`Tensor.vector_reduce`](quimb.tensor.Tensor.vector_reduce)
- [`contract_compressed`](quimb.tensor.TensorNetwork.contract_compressed), default to 'virtual-tree' gauge
- add [`TN_rand_tree`](quimb.tensor.TN_rand_tree)
- `experimental.operatorbuilder`: fix parallel and heisenberg builder
- make parametrized gate generation even more robost (ensure matching types
so e.g. tensorflow can be used)

**Bug fixes:**

- fix gauge size check for some backends

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