I am facing an issue regarding the implementation of two site MPO operators with a density matrix.

Basically, I have evolved a density matrix and want to calculate the spin current at each time-steps.

```
\rho(t) = \exp(-iHt/h) \rho(0) \exp(iHt/h)
```

For this, I have used this implementation https://github.com/ITensor/ITensors.jl/blob/main/examples/gate_evolution/mpo_gate_evolution.jl

Now, I want to calculate the spin current < I*i (t)> = Tr{\rho(t) J*i}

where J *i = S*x ^i S*y^{i+1} - S*y^i S_x^{i+1}

My implementation in ITensor Julia

p = AutoMPO()

p+= 1,"Sx",50,"Sy",51

p+= -1,"Sy",50,"Sx",51

Operator = MPO(p,s)

I*50 = inner(Operator,rho*t)

But, I am getting zero as the output for I_50 at every time step. I would appreciate it if you could look into the issue.