Ignorance is bliss: general and robust cancellation of decoherence via no-knowledge quantum feedback

Stable charging of a Rydberg quantum battery in an open system

The charging of an open quantum battery is investigated where the charger and the quantum battery interact with a common environment. At zero temperature, the stored energy of the battery is optimal as the charger and the quantum battery share the same coupling strength (g_{C}=g_{B}). By contrast, in the presence of the quantum jump-based feedback control, the energy stored in the battery can be greatly enhanced for different couplings (g_{C}>g_{B}). Considering the feasibility of the experiment, a model of Rydberg quantum battery is proposed with cascade-type atoms interacting with a dissipative optical cavity. The effective coupling strength between the charger (quantum battery) and the cavity field is hence adjustable and one can make the battery close to perfect excitation. The adverse factors of charging quantum batteries such as time delay for feedback, finite temperature, and spontaneous emission of Rydberg atoms are also discussed, and the result shows that the quantum battery is still able to retain a satisfactory energy storage effect.

Quantum control study of ultrafast optical responses in semiconductor quantum dot devices

Two quantum control spectroscopic techniques were applied to study InAs quantum dot (QD) devices, which contain different strain-reducing layers. By adaptively control light matter interaction, a delayed resonant response from the InAs QDs was found to be encoded into the optimal phase profile of ultrafast optical pulse used. We verified the delayed resonant response to originate from excitons coupled to acoustic phonons of InAs QDs with two-dimensional coherent spectroscopy. Our study yields valuable dynamical information that can deepen our understanding of the coherent coupling process of exciton in the quantum-confined systems.