support for empty Pauli string(a string full of pauli I) ?

[overshiki]

Hi, I'm trying to use Yao.jl in the field of quantum chemistry. I just encountered a problem that I do not know how to write an empty Pauli string inside a Hamiltonian. More specifically, I need to write down the following Hamiltonian, for example:

H = 0.13*I1*I2*I3 + 0.6*X1*I2*Z3 + 0.3*I1*X2*Z3 ...

Following this example, I know that 0.6*X1*I2*Z3 + 0.3*I1*X2*Z3 could be defined in this way:

function hamiltonian()
    X1 = put(3,1=>X)
    X2 = put(3,2=>X)
    Z3 = put(3,3=>Z)
    0.6*X1*Z3 + 0.3*X2*Z3
end

But how about 0.13*I1*I2*I3? I tried 0.13 + 0.6*X1*Z3 + 0.3*X2Z3, however, it doesn't work. I think it must be an easy task, but I could not find any related document.

[ChenZhao44]

Hi, overshiki.

Maybe you could try this:

function hamiltonian()
    X1 = put(3, 1=>X)
    X2 = put(3, 2=>X)
    Z3 = put(3, 3=>Z)
    I = put(3, 1=>I2)
    return 0.13*I + 0.6*X1*Z3 + 0.3*X2*Z3
end

[overshiki]

Hi @ChenZhao44, Yes, this solves my problem. Thanks!