Hi all !

I’m happy to announce PauliStrings.jl a quantum many body simulation package based on the Pauli strings representation.

Docs : https://paulistrings.org/

Paper : [2410.09654] Quantum many-body simulations with PauliStrings.jl

It’s particularity adapted for time evolving noisy spin systems, running Lanczos algorithm, and simulating systems on arbitrary geometries.

The main idea is to store operators as a sum of Pauli strings and apply some truncation of the number of strings or string length to make simulations tractable.

You can construct operators in a similar manner to ITensors MPO’s.

For example, the following code constructs a XX hamiltonian and computes the first 20 lanczos coefficients:

```
using PauliStrings
function XX(N)
H = Operator(N)
for j in 1:(N - 1)
H += "X",j,"X",j+1
H += "Z",j,"Z",j+1
end
return H
end
function X(N)
H = Operator(N)
for j in 1:N
H += "X",j
end
return H
end
N = 50 # system size (spins)
H = XX(N) # hamiltonian
O = X(N) # operator
# 20 lanczos coeficients, keep 2^20 strings at each step
b = lanczos(H, O, 20, 2^20)
```