报告时间：6月21日 周三 下午3:00
报告人：Xin (Sunny) Wang王欣（香港城市大学助理教授）
报告题目： Quantum teleportation over fibre network towards a global quantum internet
Overcoming the charge noise is key to the realization of scalable quantum computation using spin qubits. It has been recently demonstrated that the effects of charge noise can be suppressed if operations of a singlet-triplet qubit are implemented using barrier control instead of the traditional tilt control.
We have found, however, that for certain gates involving extensive x-rotations, barrier control offers little or no improvement when the nuclear noise is significant. Nevertheless, we introduce a new set of composite pulses that reduce gate times by up to 90%.
Using these optimized pulses, the barrier control shows great advantages in randomized benchmarking simulations, with the coherence time extended by about two orders of magnitude for experimentally relevant noises . We have also performed a microscopic calculation of a singlet-triplet qubit under the influence of an impurity. We have found that, the relative charge noise (charge noise divided by the exchange interaction), while generally believed to increase with increasing exchange interaction, actually decreases when the barrier control is implemented .
This is understood as a combined consequence of the greatly suppressed detuning noise when the two dots are symmetrically operated, as well as an enhancement of the inter-dot hopping energy of an electron when the barrier is lowered.
 C. Zhang, R.E. Throckmorton, X.-C. Yang, X. Wang, E. Barnes, S. Das Sarma, Phys. Rev. Lett. 118, 216802 (2017)
 X.-C. Yang, X. Wang, arXiv:1704.07975, (Phys. Rev. A in press)
Dr. Xin (Sunny) Wang received his B.S. in Physics from Peking University, China, in 2005. He then went to the United States for graduate study in Columbia University in the City of New York, where he received Ph.D. in Physics in 2010. His Ph.D. study was focused on the theory of strongly correlated materials, in particular the high-temperature superconductors. From 2010-2015, Dr. Wang was a Research Associate in Condensed Matter Theory Center at University of Maryland, College Park, U.S.A. He joined City University of Hong Kong in 2015. His current research interest mainly lies in the field of quantum computation and
quantum control with spin systems.