Instituta za fiziku
Laboratorija za optiku i lasere
U ponedeljak 23. juna 2008. godine u 13 sati, u biblioteci Instituta za fiziku
Spin squeezing for atomic clock below the standard quantum limit
Prof Vladan Vuletić
MIT, Cambridge, SAD
Many precision measurements with quantum mechanical two-level systems, including atomic clocks, are limited by projection noise that arises when each atom is projected randomly into one of two states in the final measurement. At this ‘standard quantum limit’ for measurements with independent atoms, the precision scales inversely as the square root of the atom number. However, it is possible to use quantum mechanical correlations between particles (entanglement) to improve on this limit. To prepare such entangled states of an atomic ensemble (spin-squeezed states), the necessary interaction between the atoms can be created by a collective measurement that does not reveal the states of the individual atoms. We demonstrate that measurement of the atomic refractive index, enhanced by an optical resonator, can produce as much as 7 dB of spin squeezing below the projection noise limit. The measurement is performed with rubidium atoms trapped on a microchip, and can be directly used for improving the precision of an atomic-clock.
Vladan Vuletic was born in Pec, Serbia, and educated in Germany. In 1992, he earned the Physics Diploma with highest honors from the Ludwig-Maximilians-Universität München, and in 1997, a Ph.D. in Physics (summa cum laude) from the same institution. While a postdoctoral researcher with the Max-Planck Institute for Quantum Optics in Garching, Germany, Professor Vuletic accepted a Lynen Fellowship at Stanford University in 1997. In 2000, he was appointed an Assistant Professor in the Department of Physics at Stanford and in June 2003 accepted an Assistant Professorship in Physics at MIT. He was promoted to Associate Professor in July 2004, and to Associate Professor with tenure in 2007.