Subject：Precision measurements beyond standard quantum limit in atomic vapor
Speaker：Prof. Yanhong Xiao
Emcee：Prof. Yanyi Jiang
Time：10:30am, 12th Jun, 2019
Place：Science Building A207
Abstract：
Measurements lay at the foundation of physical science, and their ultimate precision is normally set by the standard quantum limit (SQL). Entangled states such as spin squeezed states, squeezed light can be used to break such limit, but previous experiments have largely been proof-of-principle, i.e., the absolute precision of those measurements, although beyond SQL, is relatively low. We have recently achieved spin squeezing for more than 100 billion atoms in a macroscopic vapor cell, exceeding the best angular resolving power in any spin squeezed state so far by 1000 times, with the aid of adiabatic pulse control and motional averaging. In a similar setup, a femtotesla level atomic magnetometer operated at room temperature was demonstrated， using a new weak-measurement spectroscopy. These results show potential benefits of entangled states even in practical and high-precision systems. In parallel, we are developing novel quantum light sources such as squeezed light array, quantum correlated beam array, by employing coherent diffusion of polaritons in vapor cells.Such light sources will find applications in quantum information science as well as quantum metrology.
