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Spin squeezing in internal bosonic Josephson junctions via enhanced shortcuts to adiabaticity
Our paper on "Spin squeezing in internal bosonic Josephson junctions via enhanced shortcuts to adiabaticity" has been accepted for publication in Physical Review Applied. This work has been done in collaboration with Vladimir M. Stojanović (Technical University of Darmstadt, Germany) and emanated from research supported in part by a Grant from Science Foundation Ireland under Grant number 19/FFP/6951 (“Shortcut- Enhanced Quantum Thermodynamics”).
In this paper, we investigate a time-efficient and robust preparation of spin-squeezed states -- a class of states of interest for quantum-enhanced metrology -- in internal bosonic Josephson junctions with a time-dependent nonlinear coupling strength between atoms in two different hyperfine states.
We treat this state-preparation problem, which had previously been addressed using shortcuts to adiabaticity (STA), using the recently proposed analytical modification of this class of quantum-control protocols that became known as the enhanced STA (eSTA) method. We characterize the state-preparation process by evaluating the time dependence of the coherent spin-squeezing and number-squeezing parameters and the target-state fidelity. We show that the state-preparation times obtained using the eSTA method compare favourably to those found in previously proposed approaches. Even more importantly, we demonstrate that the increased robustness of the eSTA approach -- compared to its STA counterpart -- leads to additional advantages for potential experimental realizations of strongly spin-squeezed states.