Quimb

**Enhancements**

- refactor 'isometrize' methods including new "cayley", "householder" and
"torch_householder" methods. See :func:`quimb.tensor.decomp.isometrize`.
- add :meth:`~quimb.tensor.tensor_core.TensorNetwork.compute_reduced_factor`
and :meth:`~quimb.tensor.tensor_core.TensorNetwork.insert_compressor_between_regions`
methos, for some RG style algorithms.
- add the ``mode="projector"`` option for 2D tensor network contractions
- add HOTRG style coarse graining and contraction in 2D and 3D. See
:meth:`~quimb.tensor.tensor_2d.TensorNetwork2D.coarse_grain_hotrg`,
:meth:`~quimb.tensor.tensor_2d.TensorNetwork2D.contract_hotrg`,
:meth:`~quimb.tensor.tensor_3d.TensorNetwork3D.coarse_grain_hotrg`, and
:meth:`~quimb.tensor.tensor_3d.TensorNetwork3D.contract_hotrg`,
- add CTMRG style contraction for 2D tensor networks:
:meth:`~quimb.tensor.tensor_2d.TensorNetwork2D.contract_ctmrg`
- add 2D tensor network 'corner double line' (CDL) builders:
:func:`~quimb.tensor.tensor_builder.TN2D_corner_double_line`
- update the docs to use the `furo <https://pradyunsg.me/furo/>`_ theme,
`myst_nb <https://myst-nb.readthedocs.io/en/latest/>`_ for notebooks, and
several other `sphinx` extensions.
- add the `'adabelief'` optimizer to
:class:`~quimb.tensor.optimize.TNOptimizer` as well as a quick plotter:
:meth:`~quimb.tensor.optimize.TNOptimizer.plot`
- add initial 3D plotting methods for tensors networks (
``TensorNetwork.draw(dim=3, backend='matplotlib3d')`` or
``TensorNetwork.draw(dim=3, backend='plotly')``
). The new ``backend='plotly'`` can also be used for 2D interactive plots.
- Update :func:`~quimb.tensor.tensor_builder.HTN_from_cnf` to handle more
weighted model counting formats.
- Add :func:`~quimb.tensor.tensor_builder.cnf_file_parse`
- Add :func:`~quimb.tensor.tensor_builder.random_ksat_instance`
- Add :func:`~quimb.tensor.tensor_builder.TN_from_strings`
- Add :func:`~quimb.tensor.tensor_builder.convert_to_2d`
- Add :func:`~quimb.tensor.tensor_builder.TN2D_rand_hidden_loop`
- Add :func:`~quimb.tensor.tensor_builder.convert_to_3d`
- Add :func:`~quimb.tensor.tensor_builder.TN3D_corner_double_line`
- Add :func:`~quimb.tensor.tensor_builder.TN3D_rand_hidden_loop`
- various optimizations for minimizing computational graph size and
construction time.
- add ``'lu'``, ``'polar_left'`` and ``'polar_right'`` methods to
:func:`~quimb.tensor.tensor_core.tensor_split`.
- add experimental arbitrary hamilotonian MPO building
- :class:`~quimb.tensor.tensor_core.TensorNetwork`: allow empty constructor
(i.e. no tensors representing simply the scalar 1)
- :meth:`~quimb.tensor.tensor_core.TensorNetwork.drop_tags`: allow all tags to
be dropped
- tweaks to compressed contraction and gauging
- add jax, flax and optax example
- add 3D and interactive plotting of tensors networks with via plotly.
- add pygraphiviz layout options
- add :meth:`~quimb.tensor.tensor_core.TensorNetwork.combine` for unified
handling of combining
tensor networks potentially with structure
- add HTML colored pretty printing of tensor networks for notebooks
- add `quimb.experimental.cluster_update.py`


**Bug fixes:**

- fix :func:`~quimb.tensor.decomp.qr_stabilized` bug for strictly upper
triangular R factors.

**Full Changelog**: https://github.com/jcmgray/quimb/compare/1.4.2...v1.5.0

Add automatic building and publishing of `quimb` to `pypi`.

**Enhancements**

- unify much functionality from 1D, 2D and 3D into general arbitrary geometry
class :class:`quimb.tensor.tensor_arbgeom.TensorNetworkGen`
- refactor contraction, allowing using cotengra directly
- add :meth:`~quimb.tensor.tensor_core.Tensor.visualize` for visualizing the
actual data entries of an arbitrarily high dimensional tensor
- add :class:`~quimb.tensor.circuit.Gate` class for more robust tracking and
manipulation of gates in quantum :class:`~quimb.tensor.circuit.Circuit`
simulation
- tweak TN drawing style and layout
- tweak default gauging options of compressed contraction
- add :meth:`~quimb.tensor.tensor_core.TensorNetwork.compute_hierarchical_grouping`
- add :meth:`~quimb.tensor.tensor_core.Tensor.as_network`
- add :meth:`~quimb.tensor.tensor_core.TensorNetwork.inds_size`
- add :meth:`~quimb.tensor.tensor_core.TensorNetwork.get_hyperinds`
- add :meth:`~quimb.tensor.tensor_core.TensorNetwork.outer_size`
- improve :meth:`~quimb.tensor.tensor_core.TensorNetwork.group_inds`
- refactor tensor decompositiona and 'isometrization' methods
- begin supporting pytree specifications in `TNOptimizer`, e.g. for constants
- add `experimental` submodule for new sharing features
- register tensor and tensor network objects with `jax` pytree interface
(:pull:`150`)
- update CI infrastructure

**Bug fixes:**

- fix force atlas 2 and `weight_attr` bug (:issue:`126`)
- allow unpickling of `PTensor` objects (:issue:`128`, :pull:`131`)

**Enhancements**

- Add 2D tensor network support and algorithms
- Add 3D tensor network infrastructure
- Add arbitrary geometry quantum state infrastructure
- Many changes to :class:`TNOptimizer`
- Many changes to TN drawing
- Many changes to :class:`Circuit` simulation
- Many improvements to TN simplification
- Make all tag and index operations deterministic
- Add :func:`~quimb.tensor.tensor_core.tensor_network_sum`,
:func:`~quimb.tensor.tensor_core.tensor_network_distance` and
:meth:`~quimb.tensor.tensor_core.TensorNetwork.fit`
- Various memory and performance improvements
- Various graph generators and TN builders

**Enhancements**

- Added time dependent evolutions to :class:`~quimb.evo.Evolution` when integrating a pure state - see :ref:`time-dependent-evolution` - as well as supporting ``LinearOperator`` defined hamiltonians (:pull:`40`).
- Allow the :class:`~quimb.evo.Evolution` callback ``compute=`` to optionally access the Hamiltonian (:pull:`49`).
- Added :meth:`quimb.tensor.tensor_core.Tensor.randomize` and :meth:`quimb.tensor.tensor_core.TensorNetwork.randomize` to randomize tensor and tensor network entries.
- Automatically squeeze tensor networks when rank-simplifying.
- Add :meth:`~quimb.tensor.tensor_1d.TensorNetwork1DFlat.compress_site` for compressing around single sites of MPS etc.
- Add :func:`~quimb.tensor.tensor_gen.MPS_ghz_state` and :func:`~quimb.tensor.tensor_gen.MPS_w_state` for building bond dimension 2 open boundary MPS reprentations of those states.
- Various changes in conjunction with `autoray <https://github.com/jcmgray/autoray>`_ to improve the agnostic-ness of tensor network operations with respect to the backend array type.
- Add :func:`~quimb.tensor.tensor_core.new_bond` on top of :meth:`quimb.tensor.tensor_core.Tensor.new_ind` and :meth:`quimb.tensor.tensor_core.Tensor.expand_ind` for more graph orientated construction of tensor networks, see :ref:`tn-creation-graph-style`.
- Add the :func:`~quimb.gen.operators.fsim` gate.
- Make the parallel number generation functions use new `numpy 1.17+` functionality rather than `randomgen` (which can still be used as the underlying bit generator) (:pull:`50`)
- TN: rename ``contraction_complexity`` to :meth:`~quimb.tensor.tensor_core.TensorNetwork.contraction_width`.
- TN: update :meth:`quimb.tensor.tensor_core.TensorNetwork.rank_simplify`, to handle hyper-edges.
- TN: add :meth:`quimb.tensor.tensor_core.TensorNetwork.diagonal_reduce`, to automatically collapse all diagonal tensor axes in a tensor network, introducing hyper edges.
- TN: add :meth:`quimb.tensor.tensor_core.TensorNetwork.antidiag_gauge`, to automatically flip all anti-diagonal tensor axes in a tensor network allowing subsequent diagonal reduction.
- TN: add :meth:`quimb.tensor.tensor_core.TensorNetwork.column_reduce`, to automatically identify tensor axes with a single non-zero column, allowing the corresponding index to be cut.
- TN: add :meth:`quimb.tensor.tensor_core.TensorNetwork.full_simplify`, to iteratively perform all the above simplifications in a specfied order until nothing is left to be done.
- TN: add ``num_tensors`` and ``num_indices`` attributes, show ``num_indices`` in ``__repr__``.
- TN: various improvements to the pytorch optimizer (:pull:`34`)
- TN: add some built-in 1D quantum circuit ansatzes:
:func:`~quimb.tensor.circuit_gen.circ_ansatz_1D_zigzag`,
:func:`~quimb.tensor.circuit_gen.circ_ansatz_1D_brickwork`, and
:func:`~quimb.tensor.circuit_gen.circ_ansatz_1D_rand`.
- **TN: add parametrized tensors** :class:`~quimb.tensor.tensor_core.PTensor` and so trainable, TN based quantum circuits -- see :ref:`example-tn-training-circuits`.

**Bug fixes:**

- Fix consistency of :func:`~quimb.calc.fidelity` by making the unsquared version the default for the case when either state is pure, and always return a real number.
- Fix a bug in the 2D system example for when ``j != 1.0``
- Add environment variable `QUIMB_NUMBA_PAR` to set whether numba should use automatic parallelization - mainly to fix travis segfaults.
- Make cache import and initilization of `petsc4py` and `slepc4py` more robust.

**Enhancements**

- Added ``kraus_op`` for general, noisy quantum operations
- Added ``projector`` for constructing projectors from observables
- Added ``measure`` for measuring and collapsing quantum states
- Added ``cprint`` pretty printing states in computational basis
- Added ``simulate_counts`` for simulating computational basis counts
- TN: Add ``TensorNetwork.rank_simplify``
- TN: Add ``TensorNetwork.isel``
- TN: Add ``TensorNetwork.cut_iter``
- TN: Add ``'split-gate'`` gate mode
- TN: Add ``optimize_tensorflow.TNOptimizer`` for tensorflow based optimization
of arbitrary, contstrained tensor networks.
- TN: Add ``Dense1D.rand``
- TN: Add ``tensor_core.connect`` to conveniently set a shared index for tensors
- TN: make many more tensor operations agnostic of the array backend (e.g. numpy, cupy,
tensorflow, ...)
- TN: allow ``tensor_1d.align_TN_1D`` to take an MPO as the first argument
- TN: add ``SpinHam.build_sparse``
- TN: add ``Tensor.unitize`` and ``TensorNetwork.unitize`` to impose unitary/isometric constraints on tensors specified using the ``left_inds`` kwarg
- Many updates to tensor network quantum circuit simulation including:

* ``CircuitMPS``
* ``CircuitDense``
* 49-qubit depth 30 circuit simulation example https://quimb.readthedocs.io/en/latest/examples/ex_quantum_circuit.html

- Add ``from quimb.gates import *`` as shortcut to import ``X, Z, CNOT, ...``.
- Add ``U_gate`` for parametrized arbitrary single qubit unitary

**Bug fixes:**

- Fix ``pkron`` for case ``len(dims) == len(inds)`` (17, 18).
- Fix ``qarray`` printing for older ``numpy`` versions
- Fix TN quantum circuit bug where Z and X rotations were swapped
- Fix variable bond MPO building (22) and L=2 DMRG
- Fix ``norm(X, 'trace')`` for non-hermitian matrices
- Add ``autoray`` as dependency (21)