Can't take partial trace of non-numeric matrix

[araujoms]

Apparently this issue was fixed some years ago, but it came back: #93

Specifically, the following code fails:

import QuantumInformation
import JuMP

model = JuMP.Model()
JuMP.@variable(model, rho[1:4, 1:4] in JuMP.PSDCone())

QuantumInformation.ptrace(1.0*rho,[2,2],2)

Also, I've had compatibility problems with some packages because your Project.toml was restricting TensorOperations to version 3; I've tried removing this restriction. It caused a different error message to appear when trying to compute the partial trace.

Unrelated: you are also restricting SCS to version 1, and I'm pretty sure version 2 won't break anything.

[araujoms]

As long as this package is relying on VectorInterface it can't be fixed by design, see Jutho/VectorInterface.jl#12.

[pgawron]

I will investigate this issue.
In the meantime i checked that the following works:

Convex.partialtrace(1.0*rho,2,[2,2])