Southwest Quantum Information and Technology

Quantum control and squeezing of collective spins

Presenting Author: Daniel Hemmer, University of Arizona
Contributing Author(s): Enrique Montano, Ben Baragiola, Leigh Norris, Ezad Shojaee, Pascal Mickelson, Ivan Deutsch, Poul Jessen

Quantum control of many body atomic spins is often pursued in the context of an atom-light quantum interface, where a quantized light field acts as a “quantum bus” that can be used to entangle distant atoms. Through optimizing the spatial geometry of the atomic ensemble and light field and through control of the internal atomic state, we have improved the coherence and the amount of atom-light entanglement generated. Our basic setup consists of a quantized probe beam passing through an atom cloud held in a dipole trap, first generating spin-probe entanglement through the Faraday interaction, and then using backaction from a measurement of the probe polarization to squeeze the collective atomic spin. We achieve ~3 dB of metrologically useful spin squeezing by using a 2-color probe scheme to suppress tensor light shifts. By implementing internal state control, we have prepared and detected projection noise limited “cat” states, which have an initial projection noise that is 8 times larger than a spin coherent state in our setup. This larger projection noise leads to a further increase in atom-light coupling. We have estimated that we can generate up to ~6 dB of metrologically useful spin squeezing, which demonstrates the advantage of using the internal atomic structure as a resource for ensemble control.

(Session 5 : Thursday from 5:00 - 7:00 pm)