Calculating Purity of PurificationMPS

How do I use this algorithm? What does that parameter do?
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vmen
Posts: 5
Joined: 21 Nov 2023, 03:25

Calculating Purity of PurificationMPS

Post by vmen »

Hi,

If I have a purification MPS representing a finite temperature thermal mixed state \(\rho\), is there an efficient way I can compute the purity \(Tr[\rho^2]\) of the thermal state? I am not sure if there is even a way to compute moments of the actual thermal state from the pure MPS in the purified space. I really just need any quantity that is a monotone in purity of the represented thermal state, not necessarily the purity.

Any help is appreciated, thank you!
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