Study On Cooling And Trapping Of An Ion With Feedback

Trapping and cooling of ions play important roles in the development of quantum computation in an ion trap, while the quantum feedback method introducing interesting properties is attracting attentions of researchers at home and abroad. Now much work about study on the theory and design of quantum feedback is waiting for us to finish.We develop the master equation of ions for Doppler cooling with feedback in an ion trap, and investigate how to speed up the cooling of ions with quantum feedback by simulations. Also we consider how to decrease the effect of the stray field on ion trapping.Some novel achievements were obtained through the theoretical and simulation study of trapping and cooling of an ion with feedback:(1) We propose a cooling approach for Doppler cooling in an ion trap with feedback. This approach makes the traditional Doppler cooling of ions more effective with quantum feedback theory. By simulation research according to arguments in practical experiments, we know that we can get lower temperature with less time though quantum feedback cooling with some suitable arguments than that by traditional Doppler cooling. Additionally, at this moment different time intervals between feedback actions make little difference at cooling efficiency. Obviously, however, we cannot break through the limit of Doppler cooling.(2) We design a new method depending on feedback system to deal with the stray field. Having the average displacement through detecting the mirror-mode fluorescence, we can derive the stray field and offer a real-time compensation to get a more steady trap. Our simulations show that the compensation is quite effective.