kronecker product

[Romuald P.]

Hello everyone

I am trying to use the Kronecker Product, aka the Tensor Product of sympy.physics.quantum:

from sympy.physics.quantum import TensorProduct

from sympy.physics.quantum.pauli import SigmaZ

When applied to the product of an identity matrix with a Pauli Matrix, say sz, I get:

I =sym.eye(2)
SzA = TensorProduct(SigmaZ(),I)
print(SzA)

> SigmaZ()xMatrix([ [1, 0], [0, 1]])

The problem is with the product of I x Sigmaz:

SzB = TensorProduct(I,SigmaZ())

I get an error:

TypeError: Sequence of Matrices expected, got: (Matrix([ [1, 0], [0, 1]]), SigmaZ())

I can however get out of this issue by using the represent function

from sympy.physics.quantum import represent

I =sym.eye(2)
SzA = TensorProduct(represent(SigmaZ()),I)

SzB = TensorProduct(I,represent(SigmaZ()))

But I would like to understand why the second product (TensorProduct(I,SigmaZ())) is not allowed - or conversely why the first product (TensorProduct(SigmaZ(),I)) does not yield an error.

Thank for your help

Romuald