New feature: optimised distributed algorithms

[TysonRayJones]

contributors: Jakub Adamski, Balint Koczor, Simon Benjamin and Tyson Jones
release: v4

QuEST's backend is being refactored in order to leverage the novel, asymptotically improved algorithms of this manuscript. These techniques speedup almost all of QuEST's operators while reducing some of their memory footprints, and enable more advanced facilities (like partial traces).

• developer benefits

  • Cleaner, simpler code which leverages many mathematical simplifications.

• user benefits

  • Faster code, especially in distributed settings.
  • It is no longer necessary to pass a "temporary" Qureg to functions like calcExpecPauliHamil(psi, hamil, temp).

[TysonRayJones]

demonstrated in 8213557