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Spinor Bose-Einstein Condensates for many-particle entanglement

Final Report Summary - SCOPE (Spinor Bose-Einstein Condensates for many-particle entanglement)

Project context and objectives

The 2001 Nobel Prize for Physics was awarded jointly to Eric A. Cornell, Wolfgang Ketterle and Carl E. Wieman 'for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates'.

This realisation of degenerate bosonic gases made a system available to scientists in which extremely low temperatures can be reached in a relatively isolated environment. Bose-Einstein condensates are well-controlled, mesoscopic quantum objects that provide an ideal platform where central ideas in quantum mechanics, such as decoherence or the existence of a 'quantum-classical' boundary, can be tested. The unusual features of quantum mechanics can be probed by producing so-called entangled states and typically measuring correlations that are unexplainable using a purely classical theory. The goal of this project relates to experimentally producing such entangled states in spin 1 Bose-Einstein condensates, where three distinguishable Zeeman components with spin projection mF = 0, ±1 exist, to demonstrate the non-classical correlations built in these many-particle systems and how they undergo decoherence.

Work performed

The project made a decisive step in this direction by allowing the construction of an experimental apparatus that was able to produce spin-1 Sodium Bose-Einstein condensates. This required several experimental advances, such as developing a new Sodium atomic source, a new laser system for laser cooling and a new method for all-optical evaporation. In parallel, the robustness of entangled states and of their preparation methods to inelastic collisions or experimental imperfections were studied theoretically.

Main results

By producing entangled states (for instance, a twin Fock state with exactly half of the atoms in the +1 and -1 components) is realistic for mescoscopic samples, which contain between a few tens and a hundred atoms.