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update doc devices
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josephleekl committed Jan 9, 2025
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2 changes: 1 addition & 1 deletion doc/lightning_gpu/device.rst
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Expand Up @@ -142,7 +142,7 @@ Each problem is unique, so it can often be best to choose the default behaviour

**Multi-GPU/multi-node support:**

The ``lightning.gpu`` device allows users to leverage the computational power of many GPUs sitting on separate nodes for running large-scale simulations.
The ``lightning.gpu`` device allows users to leverage the computational power of many GPUs distributed across multiple nodes for running large-scale simulations.
Provided that NVIDIA ``cuQuantum`` libraries, a ``CUDA-aware MPI`` library and ``mpi4py`` are properly installed and the path to the ``libmpi.so`` is
added to the ``LD_LIBRARY_PATH`` environment variable, the following requirements should be met to enable multi-node and multi-GPU simulations:

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8 changes: 4 additions & 4 deletions doc/lightning_tensor/device.rst
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Lightning Tensor device
=======================

The ``lightning.tensor`` device is a tensor network simulator, supporting both the Matrix Product State (MPS) and Exact Tensor Network methods. The device is built on top of the `cutensornet <https://docs.nvidia.com/cuda/cuquantum/latest/cutensornet/index.html>`__ from the NVIDIA cuQuantum SDK, enabling GPU-accelerated simulation of quantum tensor network evolution. This device is designed to simulate large-scale quantum circuits using tensor networks. For small circuits, state-vector simulator plugins may be more suitable.
The ``lightning.tensor`` device is a tensor network simulator, supporting both the Matrix Product State (MPS) and Exact Tensor Network methods. The device is built on top of the `cutensornet <https://docs.nvidia.com/cuda/cuquantum/latest/cutensornet/index.html>`__ library from the NVIDIA cuQuantum SDK, enabling GPU-accelerated simulation of quantum tensor network evolution. This device is designed to simulate large-scale quantum circuits using tensor networks. For small circuits, state-vector simulator plugins may be more suitable.

The ``lightning.tensor`` device defaults to the Matrix Product State (MPS) method, and can be loaded using:

Expand All @@ -15,7 +15,7 @@ The default setup for the MPS tensor network approximation is:
- ``max_bond_dim`` (maximum bond dimension) defaults to ``128`` .
- ``cutoff`` (singular value truncation threshold) defaults to ``0`` .
- ``cutoff_mode`` (singular value truncation mode) defaults to ``abs`` , considering the absolute values of the singular values; Alternatively, users can opt to set ``cutoff_mode`` to ``rel`` to consider the relative values of the singular values.
Note that the ``cutensornet`` will automatically determine the reduced extent of the bond dimension based on the lowest among the multiple truncation cutoffs (``max_bond_dim``, ``cutoff-abs`` and ``cutoff-rel``). For more details on how the ``cutoff`` works, please check the `cuQuantum documentation <https://docs.nvidia.com/cuda/cuquantum/latest/cutensornet/api/types.html#cutensornettensorsvdconfigattributes-t>`__.
Note that the ``cutensornet`` will automatically determine the reduced extent of the bond dimension based on the lowest among the multiple truncation cutoffs (``max_bond_dim``, ``cutoff-abs`` or ``cutoff-rel``). For more details on how the ``cutoff`` works, please check the `cuQuantum documentation <https://docs.nvidia.com/cuda/cuquantum/latest/cutensornet/api/types.html#cutensornettensorsvdconfigattributes-t>`__.

Users also have the flexibility to customize MPS parameters according to their specific needs with:

Expand All @@ -40,7 +40,7 @@ Users can also run the ``lightning.tensor`` device in the **Exact Tensor Network
import pennylane as qml
dev = qml.device("lightning.tensor", wires=100, method="tn")
The ``lightning.tensor`` device dispatches all operations to be performed on a CUDA-capable GPU of generation SM 7.0+
The ``lightning.tensor`` device dispatches all operations to be performed on a CUDA-capable GPU of generation SM 7.0
and greater (Volta and later). This device supports both exact and finite shots measurements. Currently, the supported differentiation methods are parameter-shift and finite-diff. Note that the MPS backend of ``lightning.tensor`` supports multi-wire gates via Matrix Product Operators (MPO).

The ``lightning.tensor`` device is designed for expectation value calculations. Measurements of :func:`~pennylane.probs` or :func:`~pennylane.state` return dense vectors of dimension :math:`2^{\text{n_qubits}}`, so they should only be used for small systems.
Expand All @@ -57,7 +57,7 @@ The ``lightning.tensor`` device allows users to get quantum circuit gradients us
Check out the :doc:`/lightning_tensor/installation` guide for more information.

Note that as ``lightning.tensor`` cannot be cleaned up like other state-vector devices because the data is attached to the graph. It is recommended to create a new ``lightning.tensor`` device per circuit to ensure resources are correctly handled.
Note that ``lightning.tensor`` cannot be cleaned up like other state-vector devices since the data is attached to the graph. It is recommended to create a new ``lightning.tensor`` device per circuit to ensure resources are correctly handled.

.. seealso:: `DefaultTensor <https://docs.pennylane.ai/en/latest/code/api/pennylane.devices.default_tensor.DefaultTensor.html>`__ for a CPU only tensor network simulator device.

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