Controlling population dynamics in open two-level quantum systems

Gustavo Fernandes da Costa, Emanuel F. de Lima

We address the control of the dynamics of both population and coherence phase in an open two-level quantum system employing a single external control field. The system dynamics is described by a Markovian master equation that takes into account dephasing and thermal noise. The control is engineered by inverting the underlying equations of motion, which yields an analytical expression for the control field in terms of user-specified time-dependent functions for the population and coherence phase. Our approach allows us to dictate not only the initial and final populations and phases, but the full dynamics of these quantities. The chosen functions for population and phase have to conform to certain constraints indicated in our analysis. Our methodology also reveals the possible transitions for given initial conditions and environmental noise parameters.

Thomas Müller, Wolfgang Parz, Rudolf Bratschitsch +2 more

V. M. Akulin, É. P. Garsevanishvili

Felipe Silveira Fagundes, Emanuel F. de Lima

We consider the simultaneous control of the relative phase and populations of two-level quantum systems by an external field. We apply a reverse engineering approach, obtaining an analytical expression for the control field depending upon two user-defined functions that dictate the population and the relative phase dynamics. We show that, in general, the prescribed functions for the dynamics cannot be chosen arbitrarily, but still there is plenty of room for choice. We illustrate the reverse engineering technique for several target states using different kinds of functions to specify the system dynamics. We show that by adjusting these dynamical functions, we produce different kinds of control fields. These controls can be easily built, needing, apart from the dynamical function themselves, only their first derivatives. The methodology presented here will certainly find many applications that go beyond simple two-level systems.

Ri‐Hua Zheng, Wen Ning, Zhen‐Biao Yang +2 more

Abstract We propose a method for the dynamical control in three-level open systems and realize it in the experiment with a superconducting qutrit. Our work demonstrates that in the Markovian environment for a relatively long time (3 μs), the systemic populations or coherence can still strictly follow the preset evolution paths. This is the first experiment for precisely controlling the Markovian dynamics of three-level open systems, providing a solid foundation for the future realization of dynamical control in multiple open systems. An instant application of the technique demonstrated in this experiment is to stabilize the energy of quantum batteries.

M. Kira, S. W. Koch