QEngine: A C++ library for quantum optimal control of ultracold atoms

Abstract

We present the first version of the QEngine, an open-source C++ library for simulating and controlling ultracold quantum systems using optimal control theory (OCT). The most notable systems presented here are Bose-Einstein condensates, many-body systems described by Bose-Hubbard type models, and two interacting particles. These systems can all be realized experimentally using ultracold atoms in various trapping geometries including optical lattices. In addition we provide a number of optimal control algorithms including the recently introduced group method. The QEngine library has a strong focus on accessibility and performance. We provide several examples of how to prepare simulations of the physical systems and apply optimal control.

Hessian-based optimization of constrained quantum control

“…Perhaps just as crucially, the derivation and use of an analytically exact gradient of the quantum dynamics used in grape (see below) enables the precision needed for bfgs to outclass its first-order counterpart [18]. It is now the standard within quantum optimal control theory [19,40,41].…”

“…grape has been widely successful providing its use in Nuclear Magnetic Resonance [21][22][23][24][25], superconducting qubit circuits [26][27][28][29][30], spin chains [31][32][33][34], Nitrogen vacancy centers [35,36], and ultra cold atoms [37,38]. It has also become a standard integrated tool in many numerical packages aimed at quantum physicists [19,[39][40][41]. Further, one could mention the many extensions of grape, which treat filtering [42], robustness [17], chopped random basis [43], experiment design [44], * sherson@phys.au.dk and open quantum systems [45].…”

Krotov: A Python implementation of Krotov's method for quantum optimal control

“…This approach has recently been named "GRadient Optimization Using Parametrization" (GROUP) [90]. An implementation of several variants of GROUP is available in the QEngine C++ library [91]. An alternative for a moderate number of control parameters is "gradient-optimization of analytic controls" (GOAT) [92].…”

qopt: An experiment-oriented Qubit Simulation and Quantum Optimal Control Package

“…QuTiP's extension by the subpackage for quantum information processing introduces the capability to simulate quantum gates on the pulse level with the option to include noise but without optimal control techniques. There are also special purpose optimization frameworks like QEngine [34] for ultracold atoms or Pulser [35] for neutral-atom arrays. Some of these implementations can be generalized to noisy systems if an open system description based on master equations is adopted [36], thus readily treating Markovian noise.…”