# Using the observer system with TDVP

**URL:** <https://itensor.discourse.group/t/using-the-observer-system-with-tdvp/1754>\
**Category:** ITensor Julia Questions\
**Tags:** tdvp\
**Created:** [May 24, 2024, 3:11pm UTC](https://itensor.discourse.group/t/using-the-observer-system-with-tdvp/1754 "2024-05-24T15:11:44Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![joshperry3110](https://avatars.discourse-cdn.com/v4/letter/j/839c29/32.png) [@joshperry3110](https://itensor.discourse.group/u/joshperry3110)\
**Post date:** [May 24, 2024, 3:11pm UTC](https://itensor.discourse.group/t/using-the-observer-system-with-tdvp/1754/1 "2024-05-24T15:11:44Z")

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Hi,  
I was hoping you could give some guidance on using the observer system within TDVP. I am having trouble finding any documentation for this.  
I am interesting in measuring various expectation values of the MPS at specific times, i.e. t=0.1, 1.0, 2.0 ect.  
Is there a way to do this with the observer system? Any guidance is appreciated.  
Thanks!

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**Author:** ![mtfishman](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/mtfishman/32/11_2.png) [@mtfishman](https://itensor.discourse.group/u/mtfishman)\
**Post date:** [May 24, 2024, 3:39pm UTC](https://itensor.discourse.group/t/using-the-observer-system-with-tdvp/1754/2 "2024-05-24T15:39:19Z")

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Take a look at these examples: [ITensorMPS.jl/examples at main · ITensor/ITensorMPS.jl · GitHub](https://github.com/ITensor/ITensorMPS.jl/tree/main/examples)

The ITensorMPS.jl package is under-documented right now since we are planning on reorganizing the MPS and MPO code that is currently distributed across ITensors.jl and ITensorTDVP.jl into ITensorMPS.jl ([[ANN] ITensorMPS.jl initial release](https://itensor.discourse.group/t/ann-itensormps-jl-initial-release/1717)) but once we move all of the MPS and MPO code to ITensorMPS.jl we will do a better job of documenting the solvers that are currently in ITensorTDVP.jl.

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/itensor/original/1X/d3072b13e047cd06df7f3981547c0917d940dfa4.png) [@system](https://itensor.discourse.group/u/system)\
**Post date:** [June 3, 2024, 3:39pm UTC](https://itensor.discourse.group/t/using-the-observer-system-with-tdvp/1754/3 "2024-06-03T15:39:31Z")

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