Fidelity greater than 1?

[Mauricio Reis]

Hi there,

I was investigating a quantum dynamics and decided to compare two evolutions of the same initial state: one by mesolve and the other by ode2es. In the two scripts I was running the full 2 partite states and taking the partial trace over the second to get \rho1(t), in both cases. To compare the results, I took the fidelity between the generated states. I've noticed the fidelity could become greater than 1 at many time samples. To further investigate it, I took the fidelity of one state with itself and checked it happened again, withing a range of 1e-7. Was that expected? I am running qutip 4.2 with the latest Anaconda distribution (I guess my numpy package is also updated).

[Mauricio Reis]

Just adding an info:

this is my qt.run() head information:
QuTiP: Quantum Toolbox in Python

Copyright (c) 2011 and later.

A. J. Pitchford, P. D. Nation, R. J. Johansson, A. Grimsmo, and C. Granade

QuTiP Version: 4.2.0

Numpy Version: 1.13.3

Scipy Version: 1.0.0

Cython Version: 0.27.3

Matplotlib Version: 2.1.1

Python Version: 3.6.3

Number of CPUs: 4

BLAS Info: INTEL MKL

OPENMP Installed: False

INTEL MKL Ext: True

Platform Info: Windows (AMD64)