Controlling the uncontrollable: Quantum control of open system dynamics

Abstract

Control of open quantum systems is an essential ingredient to the realization of contemporary quantum science and technology. We demonstrate such control by employing a thermodynamically consistent framework, taking into account the fact that the drive can modify the interaction with environment. Such an effect is incorporated within the dynamical equation, leading to control dependent dissipation, this relation serves as the key element for open system control.Thermodynamics of the control process is reflected by a unidirectional flow of energy to the environment resulting in large entropy production. The control paradigm is displayed by analyzing entropy changing state to state transformations, such as heating and cooling. In addition, the generation of quantum gates under dissipative conditions is demonstrated for both non-unitary reset maps with complete memory loss and a universal set of single and double qubit unitary gates.

Quantum optimal control in quantum technologies. Strategic report on current status, visions and goals for research in Europe

“…Optimal control has been combined with time-convolutionless master equations [55,627] which allowed for studying, respectively, qubit reset and instantaneous tracking under non-Markovian dynamics. Such a combination allows for investigating the impact of control on dissipators [55,320], as a means to implement QOCT for quantum reservoir engineering [293]. The simplest way to treat memory effects consists in employing structured environments that are partitioned into strongly and weakly coupled modes [31,56,58,230,486].…”

Quantum optimal control in quantum technologies. Strategic report on current status, visions and goals for research in Europe

“…Optimal control has been combined with timeconvolutionless master equations [53,621] which allowed for studying, respectively, qubit reset and instantaneous tracking under non-Markovian dynamics. Such a combination allows for investigating the impact of control on dissipators [53,316], as a means to implement QOCT for quantum reservoir engineering [289]. The simplest way to treat memory effects consists in employing structured environments that are partitioned into strongly and weakly coupled modes [31,52,56,227,482].…”

“…(b) Certain control task require a change of entropy, such as reset or thermalization [52,56,166,168,227,558,559]. Tasks that do not require a change of entropy may still benefit from it, for example by reaching the target while actively cooling [316,415]. (c) Quantum control can be used to optimize the operation cycle of heat engines and refrigerators [168,213,323,626].…”

“…Preserving entropy or, minimizing decoherence is another legitimate control task. When considering protecting quantum gates from dissipation, active cooling is possible while performing the quantum operation [316]. An alternative strategy is to formulate the control in a decoherence free subspace [294,424,618], or in a path independent control [394,395].…”

“…The energetic cost in quantum thermodynamics is reflected by the first law [530]; and the cost of quantum gates has been analyzed [9,175]. A different viewpoint is accounting for irreversible entropy generation required for control [316,330]. The real resource for control is coherence.…”