# How can I separately conserve QNs which have the same name (c++)?

**URL:** <https://itensor.discourse.group/t/how-can-i-separately-conserve-qns-which-have-the-same-name-c/1222>\
**Category:** ITensor C++ Questions\
**Tags:** cpp\
**Created:** [October 16, 2023, 8:15am UTC](https://itensor.discourse.group/t/how-can-i-separately-conserve-qns-which-have-the-same-name-c/1222 "2023-10-16T08:15:48Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Wenqi](https://avatars.discourse-cdn.com/v4/letter/w/46a35a/32.png) [@Wenqi](https://itensor.discourse.group/u/Wenqi)\
**Post date:** [October 16, 2023, 8:15am UTC](https://itensor.discourse.group/t/how-can-i-separately-conserve-qns-which-have-the-same-name-c/1222/1 "2023-10-16T08:15:48Z")

</div>

Hello,

I have read the instruction on the website “[Quantum Number (QN) FAQs · ITensors.jl](https://itensor.github.io/ITensors.jl/dev/faq/QN.html)”. It works well for the Julia version. These days, I find the runtime of ITensor C++ is much shorter than ITensor Julia for my cluster. But I don’t know how to deal with “the physically distinct types of sites with identically named quantum number” in the C++ version. Could you please give me some guidance? Thank you very much!