qutip/qutip: QuTiP 4.4.0

The release of QuTiP 4.4.0

• MAJOR FEATURE: Added methods and techniques to the stochastic solvers (by Eric Giguère) which allows to use a much broader set of solvers and much more efficiently.

• MAJOR FEATURE: Optimization of the montecarlo solver (by Eric Giguère). Computation are faster in many cases. Collapse information available to time dependant information.

• Added the QObjEvo class and methods (by Eric Giguère), which is used behind the scenes by the dynamical solvers, making the code more efficient and tidier. More built-in function available to string coefficients. The coefficients can be made from interpolated array with variable timesteps and can obtain state information more easily. Time-dependant collapse operator can have multiple terms.

• New wigner_transform and plot_wigner_sphere function. (by Nithin Ramu).

• ptrace is faster and work on bigger systems, from 15 Qbits to 30 Qbits.

• QIP module: added the possibility for user-defined gates, added the possibility to remove or add gates in any point of an already built circuit, added the molmer_sorensen gate, and fixed some bugs (by Boxi Li).

• Added the quantum Hellinger distance to qutip.metrics (by Wojciech Rzadkowski).

• Implemented possibility of choosing a random seed (by Marek marekyggdrasil).

• Added a code of conduct to Github.

• Fixed bug that made QuTiP incompatible with SciPy 1.3.

• quite.cite() is improved.

• Added matplotlib as optional dependency and updated numpy and scipy requirements.

• Fixed matrix generating coherent spin states in qutip.piqs to include complex coefficients.