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arXiv:1506.03673

An entangling atomtronic beamsplitter

Chianca, C. V., M. K. Olsen

Published Jun 11, 2015• 0 citations
arXivHTMLPDF

Abstract

We propose and analyse the use of a three-well Bose-Hubbard model for the creation of two spatially separated entangled atomic samples. Our three wells are in a linear configuration, with all atoms initially in the middle well, which gives some spatial separation of the two end wells. The evolution from the initial quantum state allows for the development of entanglement between the atomic modes in the two end wells. Using inseparability criteria developed by Hillery and Zubairy, we show how the detected entanglement is time dependent, oscillating with the well occupations. We suggest and analyse a method for preserving the entanglement by turning off the different interactions when it reaches its first maximum. We analyse the system with both Fock and coherent initial states, showing that the violations of the Hillery-Zubairy inequality exist only for initial Fock states and that the collisional nonlinearity degrades them. This system is an early step towards producing entangled atomic samples that can be spatially separated and thus close the locality loophole in tests of non-local quantum correlations.

DOI
10.48550/arxiv.1506.03673

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We propose and analyse the use of a three-well Bose-Hubbard model for the creation of two spatially separated entangled atomic samples. Our three wells are in a linear configuration, with all atoms initially in the middle well, which gives some spatial separation of the two end wells. The evolution from the initial quantum state allows for the development of entanglement between the atomic modes in the two end wells. Using inseparability criteria developed by Hillery and Zubairy, we show how the detected entanglement is time dependent, oscillating with the well occupations. We suggest and analyse a method for preserving the entanglement by turning off the different interactions when it reaches its first maximum. We analyse the system with both Fock and coherent initial states, showing that the violations of the Hillery-Zubairy inequality exist only for initial Fock states and that the collisional nonlinearity degrades them. This system is an early step towards producing entangled atomic samples that can be spatially separated and thus close the locality loophole in tests of non-local quantum correlations.
We propose and analyze the use of a three-well Bose-Hubbard model for the creation of two spatially separated entangled atomic samples. Our three wells are in a linear configuration, with all atoms initially in the middle well, which gives some spatial separation of the two end wells. The evolution from the initial quantum state allows for the development of entanglement between the atomic modes in the two end wells. We show how the detected entanglement and the well occupations are time dependent. We propose a method for preserving the en-tanglement by turning off the different interactions when it reaches its first maximum. We analyze the system with both Fock and coherent initial states, showing that the violations of the chosen inequality exist only for initial Fock states and that the collisional nonlinearity degrades them. This system is a preliminary step towards producing entangled atomic samples that can be spatially separated using recently developed methods of potential manipulation and thus help close the locality loophole in tests of quantum mechanics.
Spin changing collisions in alkaline Bose-Einstein condensates can be employed to generate highly entangled atomic quantum states. Here, we will report on the generation of two classes of entangled states. Firstly, we demonstrate the generation of two-mode squeezed vacuum states and record their characteristic quadrature correlations by atomic homodyning. We prove that the correlations fulfill Reid’s criterion [1] for continuous-variable Einstein-Podolsky-Rosen entanglement. The homodyne measurements allow for a full tomographic reconstruction, yielding a two-mode squeezed state with a 78% fidelity. The created state can be directly applied to atom interferometry, as is exemplified by an atomic clock measurement beyond the Standard Quantum Limit. Secondly, we demonstrate entanglement between two spatially separated atomic modes. The entangled state is obtained by spatially splitting a Twin Fock state of indistinguishable atoms along a line of zero density. This structure of two separated atomic modes is obtained by utilizing an excited trap mode. The non-classical correlations between these atomic modes are verified by applying a novel entanglement criterion especially sensitive for our case. The method opens a path to exploit the recent success in the creation of many-particle entanglement in ultracold atoms for the field of quantum information, where individually addressable subsystems are required. Finally, we will show how the measurement protocol can be extended to perform a Bell test of quantum nonlocality. [1] M. Reid, Phys. Rev. A 40, 913-923 (1989)
We study the dynamics of entanglement and atomic populations of ultracold dipolar bosons in an aligned three-well potential described by an extended Bose-Hubbard model. We focus on a sufficiently strong interacting regime where the couplings are tuned to obtain an integrable system, in which the time evolution exhibits a resonant behavior that can be exactly predicted. Within this framework, we propose a protocol that includes an integrability breaking step by tilting the edge wells for a short time through an external field, allowing the production of quantum states with a controllable degree of entanglement. We analyze this protocol for different initial states and show the formation of highly entangled states as well as NOON-like states. These results offer valuable insights into how entanglement can be controlled in ultracold atom systems that may be useful for the proposals of new quantum devices.
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We consider a pair of twin atoms trapped in double-well potentials. For each atom, two orthogonal spatial modes are accessible: the states $|L\ensuremath{\rangle}$ and $|R\ensuremath{\rangle}$ spatially localized in the left and right wells respectively. Furthermore the twin atoms are distinguishable thanks to an additional degree of freedom. We propose a method for experimentally quantifying the particle entanglement between these atoms which allows us to probe a violation of Bell's inequality. It is based on measuring the correlations in the atoms' momentum distribution. If the tunneling and the energy difference between the wells are tunable, then full state tomography is achievable.
We propose and analyse analogs of optical cavities for atoms using two-well Bose-Hubbard models with pumping and losses. With one well pumped, we find that both the mean-field dynamics and the quantum statistics show a quantitative dependence on the choice of damped well. Both the systems we analyse remain far from equilibrium, preserving good coherence between the wells in the steady-state. We find a small degree of quadrature squeezing and mode entanglement for some parameter regimes. Due to recent experimental advances, it should be possible to demonstrate the effects we investigate and predict.