Index of Refraction of Various Gases for Sodium Matter Waves

Schmiedmayer, Jörg; Chapman, Michael; Ekstrom, Christopher R.; Hammond, Tracy; Wehinger, Stefan; Pritchard, David E.

doi:10.1103/physrevlett.74.1043

Cited by 104 publications

(129 citation statements)

References 18 publications

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“…We note that the effect of atomic collisions in an atom interferometer was already investigated in [13]. How- ever, decoherence effects were not observed in these experiments, since the detected atoms did not change the state of the colliding gas sufficiently to leave behind the required path information for decoherence.…”

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confidence: 90%

Collisional Decoherence Observed in Matter Wave Interferometry

et al. 2003

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We study the loss of spatial coherence in the extended wave function of fullerenes due to collisions with background gases. From the gradual suppression of quantum interference with increasing gas pressure we are able to support quantitatively both the predictions of decoherence theory and our picture of the interaction process. We thus explore the practical limits of matter wave interferometry at finite gas pressures and estimate the required experimental vacuum conditions for interferometry with even larger objects.PACS numbers: 03.65.Yz,39.20.+q Matter wave interferometers are based on quantum superpositions of spatially separated states of a single particle. However, as is well known, the concept of wave-particle duality does not apply to a classical object which by definition never occupies macroscopically distinct states simultaneously. By performing interference experiments with particles of increasing complexity one can therefore probe the borderline between these incompatible descriptions.It is still a matter of debate how to explain the quantum-to-classical transition in a unified framework. Some theories contain an element beyond the unitary evolution of quantum mechanics [1, 2] -which includes the 'collapse' of the wave function as taught in many standard textbooks. Decoherence theory, on the other hand, remains within the framework of the quantum theory [3,4,5]. It explains the decay of quantum coherences as being caused by the interaction of the quantum object with its environment.So far, several decoherence experiments in atom interferometry focused on the loss of coherence due to scattering of a single [6,7] or a few [8] laser photons by an atom. Other authors proposed or realized schemes to encode which-path information in internal atomic degrees of freedom, thereby reducing the interference contrast as well, in spite of a negligible change in the atomic centerof-mass state [9,10]. These studies are complemented by experiments which quantitatively followed the decoherence of a coherent photon state in a high-finesse microwave cavity [11] or of the motional state of a trapped ion [12]. However, all these experiments worked with few-level systems and engineered environments.In the present letter we quantitatively investigate a mechanism which seems to be among the most natural and most effective sources of decoherence in our macroscopic world, namely collisions with gas particles. From the controlled suppression of quantum interference as a function of the gas pressure we are able to test both the predictions of decoherence theory and our picture of the collisional interaction.We note that the effect of atomic collisions in an atom interferometer was already investigated in [13]. How- ever, decoherence effects were not observed in these experiments, since the detected atoms did not change the state of the colliding gas sufficiently to leave behind the required path information for decoherence. In contrast to that, our experiment uses massive C 70 -fullerene molecules, and is based on a Talbot-L...

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confidence: 90%

Collisional Decoherence Observed in Matter Wave Interferometry

et al. 2003

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“…In this letter, we have described the first measurements of the index of refraction of gases for lithium waves, with an experiment similar to those performed by D. Pritchard and co-workers with sodium waves [2,3,5]. A gas cell, introduced on one of the atomic beams inside an atom interferometer, modifies the wave propagation and this modification is detected on the interference signals.…”

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confidence: 99%

“…We assume that the phase ϕ can be written ϕ = a j + b j n + c j n 2 , where the quadratic term describes the non-linearity of the piezo stage (n being the channel number). The best fit of each recording, using equation (2), provides the initial phase a j , the mean intensity I 0j and the fringe visibility V j . We thus get the effect of the gas, namely the phase shift ϕ(n gas ) = a 2 − (a 1 + a 3 )/2, and the attenuation t(n gas ) given by equation (4) (the I 0 (0)V(0) value is taken as the mean of the j = 1 and j = 3 values).…”

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First Measurements of the Index of Refraction of Gases for Lithium Atomic Waves

et al. 2007

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We report the first measurements of the index of refraction of gases for lithium waves. Using an atom interferometer, we have measured the real and imaginary parts of the index of refraction n for argon, krypton and xenon, as a function of the gas density for several velocities of the lithium beam. The linear dependence of (n − 1) with the gas density is well verified. The total collision cross-section deduced from the imaginary part of (n − 1) is in very good agreement with traditional measurements of this quantity. Finally, the real and imaginary parts of (n − 1) and their ratio ρ exhibit glory oscillations, in good agreement with calculations.

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“…de Broglie waves of massive particles are very sensitive to perturbations and may serve as efficient probes for electromagnetic fields [1], earth's rotation [2], Casimir forces [3] (or in general to detect weak forces [4]), and particle properties as, for example, the refraction index of a buffer gas [5] or the electric polarizability of an atom [6]. In interferometry, disturbance of the phase of light or matter waves in one arm of the interferometer can be measured by a displacement of the interference fringes with a sensitivity determined by the fringe wavelength and the signal-to-noise ratio (SNR).…”

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confidence: 99%

Quantum fluctuations in the image of a Bose gas

2008

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We analyze the information content of density profiles for an ultracold Bose gas of atoms and extract resolution limits for observables contained in these images. Our starting point is density correlations that we compute within the Bogoliubov approximation, taking into account quantum and thermal fluctuations beyond mean-field theory. This provides an approximate way to construct the joint counting statistics of atoms in an array of pixels covering the gas. We derive the Fisher information of an image and the associated Cramér-Rao sensitivity bound for measuring observables contained in the image. We elaborate on our recent study on position measurements of a dark soliton [Negretti et al., Phys. Rev. A 77, 043606 (2008)] where a sensitivity scaling with the atomic density as n −3/4 was found. We discuss here a wider class of soliton solutions and present a detailed analysis of the Bogoliubov excitations and the gapless (Goldstone) excitation modes. These fluctuations around the mean field contribute to the noise in the image, and we show how they can actually improve the ability to locate the position of the soliton.

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Index of Refraction of Various Gases for Sodium Matter Waves

Cited by 104 publications

References 18 publications

Collisional Decoherence Observed in Matter Wave Interferometry

Collisional Decoherence Observed in Matter Wave Interferometry

First Measurements of the Index of Refraction of Gases for Lithium Atomic Waves

Quantum fluctuations in the image of a Bose gas

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