Active cancellation of stray magnetic fields in a Bose-Einstein condensation experiment

Dedman, Colin J; Dall, Robert; Byron, Lesa; Truscott, A. G.

doi:10.1063/1.2472600

Cited by 49 publications

(39 citation statements)

References 11 publications

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“…Approximately 10 4 atoms are transferred into a vertical optical dipole trap by ramping up the intensity of a far red-detuned focused laser beam in the direction of gravity over 200 ms. The magnetic trap is switched off and the only magnetic field present is generated by our magnetic field stabilization 'nullerometer' 28 , which provides a bias magnetic field ∼1 Gauss. Then, the dipole trap is ramped down over 100 ms, resulting in a trap with harmonic frequencies of (ω x , ω y , ω z )/2π = (1800, 1800, 12) Hz.…”

Section: Methodsmentioning

confidence: 99%

Wheeler's delayed-choice gedanken experiment with a single atom

et al. 2015

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The wave-particle dual nature of light and matter and the fact that the choice of measurement determines which one of these two seemingly incompatible behaviours we observe are examples of the counterintuitive features of quantum mechanics. They are illustrated by Wheeler's famous 'delayedchoice' experiment 1 , recently demonstrated in a single-photon experiment 2 . Here, we use a single ultracold metastable helium atom in a Mach-Zehnder interferometer to create an atomic analogue of Wheeler's original proposal. Our experiment confirms Bohr's view that it does not make sense to ascribe the wave or particle behaviour to a massive particle before the measurement takes place 1 . This result is encouraging for current work towards entanglement and Bell's theorem tests in macroscopic systems of massive particles 3 .The question of whether light behaves like a particle or wave had a long and strongly contested history until the advent of quantum mechanics, where it was accepted that it could indeed exhibit either behaviour. Conversely, it was de Broglie's hypothesis of matter waves 4 that deviated from the preceding view of massive bodies exclusively as particles, which was confirmed by the electron diffraction experiments of Davisson and Germer 5 . Even more bizarrely, the way in which an experiment is performed seems to induce one of these behaviours to the exclusion of the other. The question of whether a single photon in an interferometer passes through either one arm (as a particle) or both simultaneously (as a wave) led to Wheeler devising his famous gedanken experiment, which supposed that the decision of whether to attempt to measure particle or wave behaviour is made after the photon enters the interferometer. By removing the second beamsplitter of the interferometer (Fig. 1a), which-way information is revealed 6 , which precludes an interference measurement, while inserting the beamsplitter destroys information about the path taken by the photon and re-establishes a wave interference dependent on the phase difference φ between the arms.Although many experiments have shown particle-wave duality with photons 7 , including delayed-choice schemes 8-10 , delayed-choice quantum eraser experiments 11 and entanglement swapping using delayed choice 12 , only recently has the complete scheme proposed by Wheeler been realized experimentally 2 . By simultaneously ensuring that only a single photon is present in the interferometer at once, and that the decision of interferometer configuration is relativistically separated from the photon's entry to the interferometer, it was unambiguously shown that Wheeler's supposition that such a choice affects the 'past history' of the photon was correct.Recent advances in the trapping and cooling of atoms has led to the ability to readily observe wavelike phenomena with particles that have mass, such as the interference between two Bose-Einstein condensates 13 . However, progress towards demonstrating Wheeler's experiment with massive particles, such a QR NG b |0〉 |1〉 DLD φ π /2 π /2...

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Section: Methodsmentioning

confidence: 99%

Wheeler's delayed-choice gedanken experiment with a single atom

et al. 2015

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“…x z 0.5 2 G (see figure 1 for the coordinate system) is actively stabilised to attenuate stray AC fields by over 100 fold, and shot-to-shot variations to less than 0.1mG, by independently controlling three orthogonal sets of Helmholtz coils surrounding the experimental chamber [24].…”

Section: Entanglement-based 3d Magnetic Gradiometry Methodsmentioning

confidence: 99%

Entanglement-based 3D magnetic gradiometry with an ultracold atomic scattering halo

et al. 2020

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Ultracold collisions of Bose-Einstein condensates can be used to generate a large number of counterpropagating pairs of entangled atoms, which collectively form a thin spherical shell in momentum space, called a scattering halo. Here we generate a scattering halo initially composed of pairs in a symmetric entangled state in spin, and observe a coherent oscillation with an anti-symmetric state during their separation, due to the presence of an inhomogeneous magnetic field. We demonstrate a novel method of magnetic gradiometry based on the evolution of pairwise correlation, which is insensitive to common-mode fluctuations of the magnetic field. Furthermore, the highly multimode nature and narrow radial width of scattering halos enable a 3D reconstruction of the interrogated field. Based on this, we apply Ramsey interferometry to realise a 3D spatial reconstruction of the magnetic field without the need for a scanning probe.

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“…Passive magnetic shielding is well-suited for isolating an experiment by excluding magnetic fields from a contained volume. As opposed to active stabilisation 10,16 or dynamical decoupling 17,18 , it uses materials that have high magnetic permeability µ r and so redirect the magnetic flux lines around the enclosed volume. Different materials have different properties and utilise different shielding mechanisms: high-µ r materials screen quasi-dc fields up to a few 100 Hz by flux-shunting, while highly conductive materials cancel magnetic fields induced by eddy currents oscillating at a few kHz 19,20 .…”

Section: Introductionmentioning

confidence: 99%

Design and characterization of a compact magnetic shield for ultracold atomic gas experiments

Farolfi

Trypogeorgos

Colzi

et al. 2019

Review of Scientific Instruments

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We report on the design, construction, and performance of a compact magnetic shield that facilitates a controlled, low-noise environment for experiments with ultracold atomic gases. The shield was designed to passively attenuate external slowly-varying magnetic fields while allowing for ample optical access. The geometry, number of layers and choice of materials were optimised using extensive finite-element numerical simulations. The measured performance of the shield is in good agreement with the simulations. From measurements of the spin coherence of an ultracold atomic ensemble we demonstrate a remnant field noise of 2.6 µG and a suppression of external dc magnetic fields by more than five orders of magnitude.

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Active cancellation of stray magnetic fields in a Bose-Einstein condensation experiment

Cited by 49 publications

References 11 publications

Wheeler's delayed-choice gedanken experiment with a single atom

Wheeler's delayed-choice gedanken experiment with a single atom

Entanglement-based 3D magnetic gradiometry with an ultracold atomic scattering halo

Design and characterization of a compact magnetic shield for ultracold atomic gas experiments

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