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Register a new userMeasurement of quantum states of neutrons in the Earths gravitational field
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Authors
V. V. Nesvizhevsky
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The lowest stationary quantum state of neutrons in the Earths gravitational field is identified in the measurement of neutron transmission between a horizontal mirror on the bottom and an absorber on top. Such an assembly is not transparent for neutrons if the absorber height is smaller than the height of the lowest quantum state.
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An upper limit to non-Newtonian attracive forces is obtained from the measurement of quantum states of neutrons in the Earths gravitational field. This limit improves the existing constrains in the nanometer range.
We propose a method for observation of the quasi-stationary states of neutrons, localized near the curved mirror surface. The bounding effective well is formed by the centrifugal potential and the mirror Fermi-potential. This phenomenon is an example of an exactly solvable quantum bouncer problem that could be studied experimentally. It could provide a promising tool for studying fundamental neutron-matter interactions, as well as quantum neutron optics and surface physics effects. We develop formalism, which describes quantitatively the neutron motion near the mirror surface. The effects of mirror roughness are taken into account.
This work relates to the famous experiments, performed in 1975 and 1979 by Werner et al., measuring neutron interference and neutron Sagnac effects in the earths gravitational field. Employing the method of Stodolsky in its weak field approximation, explicit expressions are derived for the two phase shifts, which turn out to be in agreement with the experiments and with the previously obtained expressions derived from semi-classical arguments: these expressions are simply modified by relativistic correction factors.
We have studied neutron quantum states in the potential well formed by the earths gravitational field and a horizontal mirror. The estimated characteristic sizes of the neutron wave functions in the two lowest quantum states correspond to expectations with an experimental accuracy. A position-sensitive neutron detector with an extra-high spatial resolution of ~2 microns was developed and tested for this particular experiment, to be used to measure the spatial density distribution in a standing neutron wave above a mirror for a set of some of the lowest quantum states. The present experiment can be used to set an upper limit for an additional short-range fundamental force. We studied methodological uncertainties as well as the feasibility of improving further the accuracy of this experiment.
The Hong-Ou-Mandel (HOM) effect is analyzed for photons in a modified Mach-Zehnder setup with two particles experiencing different gravitational potentials, which are later recombined using a beam-splitter. It is found that the HOM effect depends directly on the relativistic time dilation between the arms of the setup. This temporal dilation can be used to estimate the $gamma$ and $beta$ parameters of the parameterized post-Newtonian formalism. The uncertainty in the parameters $gamma$ and $beta$ are of the order $ 10^{-8}-10^{-12}$, depending on the quantum state employed.
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