Unstable spinor Bose-Einstein condensates are ideal candidates to create nonlinear three-mode interferometers. Our analysis goes beyond the standard SU(1,1) parametric approach and therefore provides the regime of parameters where sub-shot-noise sensitivities can be reached with respect to the input total average number of particles. Decoherence due to particle losses and finite detection efficiency are also considered. PACS numbers: 37.25.+k, 03.75.Dg, 03.75.Gg, 42.50.St Interferometers provide the most precise measurements in physics [1][2][3]. Hence, there is an urgent demand for novel theoretical proposals and experimental techniques aimed at further increasing their sensitivity. Most of the current atomic and optical interferometers are made of linear devices such as beam splitters and phase shifters. Their phase uncertainty is fundamentally bounded by the shot-noise limit ∆θ ∼ 1/ √n , when using probe states made of averagen uncorrelated particles [4,5]. In this Letter, we show that the coherent spin-mixing dynamics (SMD) in a spinor Bose-Einstein condensate (BEC) [18,19] can be exploited to realize a nonlinear threemode interferometer, as shown in Fig. 1. The SMD consists of binary collisions that coherently transfer correlated pairs of trapped atoms with opposite magnetic moment [22] from the m f = 0 to the m f = ±1 hyperfine modes, and vice versa. The probe state of the interferometer is classical, given by a condensate initially prepared in the m f = 0 mode, and quantum correlations are created by the SMD. We first study the interferometer in the mean-field limit, the m f = 0 mode operator being replaced by a c-number. This analysis is valid for a large number of particles and low transfer rates. In this case, the interferometer operations belong to the SU(1,1) group and it is possible to obtain analytical predictions for the phase sensitivity. In optical systems, where transfer rates are rather low, the probe state needs to be very intense and the SU(1,1) approach is well justified [20]. SU(1,1) optical interferometry has been theoretically discussed [20,[23][24][25] and recently experimentally realized [26]. In contrast, experiments with spinor BECs [13,27,28] can be performed well outside the mean-field regime, with probe states of a relatively small number of particles and -thanks to strong nonlinearities -comparatively high transfer rates. We have thus also implemented a full three-mode quantum analysis. Within this framework, we can rigorously provide phase sensitivity bounds with respect to the average total number of particlesn in input. For realistic values ofn, including particle losses and finite detection efficiency, SSN is obtained in a regime where quantum corrections to the mean-field picture are important.Spin-mixing interferometry with BECs. The protocol outlined in Fig. 1 follows five steps: (I) probe state preparation -we consider empty m f = ±1 modes and a BEC of averagē n atoms in the m f = 0 mode, (II) a first SMD, (III) phase encoding, and (IV) a second SMD. Finally (V) the at...
We witness multipartite entanglement in the ground state of the Kitaev chain-a benchmark model of a one dimensional topological superconductor-also with variable-range pairing, using the quantum Fisher information. Phases having a finite winding number, for both short- and long-range pairing, are characterized by a power-law diverging finite-size scaling of multipartite entanglement. Moreover, the occurring quantum phase transitions are sharply marked by the divergence of the derivative of the quantum Fisher information, even in the absence of a closing energy gap.
The interplay of quantum and thermal fluctuations in the vicinity of a quantum critical point characterizes the physics of strongly correlated systems. Here we investigate this interplay from a quantum information perspective presenting the universal phase diagram of the quantum Fisher information at a quantum phase transition. Different regions in the diagram are identified by characteristic scaling laws of the quantum Fisher information with respect to temperature. This feature has immediate consequences on the thermal robustness of quantum coherence and multipartite entanglement. We support the theoretical predictions with the analysis of paradigmatic spin systems showing symmetry-breaking quantum phase transitions and free-fermion models characterized by topological phases. In particular we show that topological systems are characterized by the survival of large multipartite entanglement, reaching the Heisenberg limit at finite temperature.
Recent experiments demonstrated the generation of entanglement by quasiadiabatically driving through quantum phase transitions of a ferromagnetic spin-1 Bose-Einstein condensate in the presence of a tunable quadratic Zeeman shift. We analyze, in terms of the Fisher information, the interferometric value of the entanglement accessible by this approach. In addition to the Twin-Fock phase studied experimentally, we unveil a second regime, in the broken axisymmetry phase, which provides Heisenberg scaling of the quantum Fisher information and can be reached on shorter time scales. We identify optimal unitary transformations and an experimentally feasible optimal measurement prescription that maximize the interferometric sensitivity. We further ascertain that the Fisher information is robust with respect to nonadiabaticity and measurement noise. Finally, we show that the quasiadiabatic entanglement preparation schemes admit higher sensitivities than dynamical methods based on fast quenches.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.