# MPS initialization

**URL:** <https://itensor.discourse.group/t/mps-initialization/671>\
**Category:** ITensor Julia Questions\
**Created:** [March 1, 2023, 1:52pm UTC](https://itensor.discourse.group/t/mps-initialization/671 "2023-03-01T13:52:34Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![EmilioRui](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/emiliorui/32/208_2.png) [@EmilioRui](https://itensor.discourse.group/u/EmilioRui)\
**Post date:** [March 1, 2023, 1:52pm UTC](https://itensor.discourse.group/t/mps-initialization/671/1 "2023-03-01T13:52:34Z")

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How can I initialize an MPS without having to execute SVD?

Let’s say I want to initialize the GHZ state  
\ket{GHZ} = \ket{00 ... 0} + \ket{11... 1}

of which I already know the MPS representation, as showed on [Matrix product state - Wikipedia](https://en.wikipedia.org/wiki/Matrix_product_state), how do I initialize it directly with the MPS without executing SVD?

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<div class="post-metadata">

**Author:** ![miles](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/miles/32/6_2.png) [@miles](https://itensor.discourse.group/u/miles)\
**Post date:** [March 1, 2023, 2:10pm UTC](https://itensor.discourse.group/t/mps-initialization/671/2 "2023-03-01T14:10:52Z")

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To do that you would need to set the tensors individually, using a formula for the GHZ state as an MPS such as the one you linked to.

For example if you’ve initialized an MPS of length N like

```julia
s = siteinds("Qubit",N)
psi = MPS(s)

```

then you can set each tensor like:

```julia
psi[1] = ...
psi[2] = ...

```

Of course in the best code you would use a loop:

```julia
for j=1:N
  psi[j] = ...
end

```

Does that answer your question?

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<div class="post-metadata">

**Author:** ![EmilioRui](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/emiliorui/32/208_2.png) [@EmilioRui](https://itensor.discourse.group/u/EmilioRui)\
**Post date:** [March 1, 2023, 2:11pm UTC](https://itensor.discourse.group/t/mps-initialization/671/3 "2023-03-01T14:11:45Z")

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yes thank you