[Show abstract][Hide abstract] ABSTRACT: Light-pulse atom interferometers rely on the wave nature of matter and its
manipulation with coherent laser pulses. They are used for precise gravimetry
and inertial sensing as well as for accurate measurements of fundamental
constants. Reaching higher precision requires longer interferometer times which
are naturally encountered in microgravity environments such as drop-tower
facilities, sounding rockets and dedicated satellite missions aiming at
fundamental quantum physics in space. In all those cases, it is necessary to
consider arbitrary trajectories and varying orientations of the interferometer
set-up in non-inertial frames of reference.
Here we provide a versatile representation-free description of atom
interferometry entirely based on operator algebra to address this general
situation. We show how to analytically determine the phase shift as well as the
visibility of interferometers with an arbitrary number of pulses including the
effects of local gravitational accelerations, gravity gradients, the rotation
of the lasers and non-inertial frames of reference. Our method conveniently
unifies previous results and facilitates the investigation of novel
[Show abstract][Hide abstract] ABSTRACT: We characterize ion chains as quantum reservoirs, which can mediate
entanglement between two objects coupled with the vibrational modes of the
chain. The systems which become entangled are the transverse vibrations of two
heavy impurity defects, embedded in the ion chain, which couple with the chain
axial modes by means of an external optical potential. General scaling
properties are verified for large chains, where we demonstrate that
entanglement is a stationary feature and does not depend on the finite size of
the physical system. We then analyze the dynamics for small chains, composed by
ten to dozens of ions, and propose a measurement scheme, which allows one to
verify the existence of the predicted entangled state.
Full-text · Article · Feb 2014 · Physical Review A
[Show abstract][Hide abstract] ABSTRACT: Atom interferometers covering macroscopic domains of space-time are a
spectacular manifestation of the wave nature of matter. Due to their unique
coherence properties, Bose-Einstein condensates are ideal sources for an atom
interferometer in extended free fall. In this paper we report on the
realization of an asymmetric Mach-Zehnder interferometer operated with a
Bose-Einstein condensate in microgravity. The resulting interference pattern is
similar to the one in the far-field of a double-slit and shows a linear scaling
with the time the wave packets expand. We employ delta-kick cooling in order to
enhance the signal and extend our atom interferometer. Our experiments
demonstrate the high potential of interferometers operated with quantum gases
for probing the fundamental concepts of quantum mechanics and general
Full-text · Article · Feb 2013 · Physical Review Letters
[Show abstract][Hide abstract] ABSTRACT: The standard model of modern cosmology, which is based on the Friedmann–Lemaître–Robertson–Walker metric, allows the definition of an absolute time. However, there exist (cosmological) models consistent with the theory of general relativity for which such a definition cannot be given since they offer the possibility for time travel. The simplest of these models is the cosmological solution discovered by Kurt Gödel, which describes a homogeneous, rotating universe. Disregarding the paradoxes that come along with the abolishment of causality in such space–times, we are interested in the purely academic question of how an observer would visually perceive the time travel of an object in Gödel's universe. For this purpose, we employ the technique of ray tracing, a standard tool in computer graphics, and visualize various scenarios to bring out the optical effects experienced by an observer located in this universe. In this way, we provide a new perspective on the space–time structure of Gödel's model.
Preview · Article · Jan 2013 · New Journal of Physics
[Show abstract][Hide abstract] ABSTRACT: We theoretically show how two impurity defects in a crystalline structure can
be entangled through coupling with the crystal. We demonstrate this with a
harmonic chain of trapped ions in which two ions of a different species are
embedded. Entanglement is found for sufficiently cold chains and for a certain
class of initial, separable states of the defects. It results from the
interplay between localized modes which involve the defects and the interposed
ions, it is independent of the chain size, and decays slowly with the distance
between the impurities. These dynamics can be observed in systems exhibiting
spatial order, viable realizations are optical lattices, optomechanical
systems, or cavity arrays in circuit QED.
Full-text · Article · Aug 2012 · Physical Review A
[Show abstract][Hide abstract] ABSTRACT: One stumbling block which limits our observation of quantum effects in
the macroscopic world is decoherence. For this reason the study of
decoherence and dissipation in open quantum systems has attracted a lot
of attention. It has been shown that the generation of long distance
entanglement is possible between oscillators via a harmonic crystal
(Wolf et al, EPL, 95(2011) 60008). The aim of this current work is to
propose an experimentally feasible setup to test the possibility of the
creation of long distance entanglement. For this purpose we consider an
ion chain in a linear Paul trap with two embedded impurities, whose
transverse modes resemble the two degrees of freedom that we aim to
entangle via the rest of the chain. With the aid of appropriately
designed laser fields, the dynamics described in (Wolf et al, EPL,
95(2011) 60008) is reproduced. The resulting entanglement between the
transverse modes of the impurities is analysed by means of the
[Show abstract][Hide abstract] ABSTRACT: Two defect particles that couple to a harmonic chain, acting as common
reservoir, can become entangled even when the two defects do not directly
interact and the harmonic chain is effectively a thermal reservoir for each
individual defect. This dynamics is encountered for sufficiently low
temperatures of the chain and depends on the initial state of the two
oscillators. In particular, when each defect is prepared in a squeezed state,
entanglement can be found at time scales at which the steady state of a single
defect is reached. We provide a microscopic description of the coupled quantum
dynamics of chain and defects. By means of numerical simulations, we explore
the parameter regimes for which entanglement is found under the specific
assumption that both particles couple to the same ion of the chain. This model
provides the microscopic setting where bath-induced entanglement can be
Full-text · Article · Dec 2011 · Physical Review A
[Show abstract][Hide abstract] ABSTRACT: This paper presents the current status and future prospects of the Space Atom Interferometer project (SAI), funded by the European Space Agency. Atom interferometry provides extremely sensitive and accurate tools for the measurement of inertial forces. Operation of atom interferometers in microgravity is expected to enhance the performance of such sensors. Main goal of SAI is to demonstrate the possibility of placing atom interferometers in space. The resulting drop-tower compatible atom interferometry acceleration sensor prototype is described. Expected performance limits and potential scientific applications in a micro-gravity environment are also discussed.
No preview · Article · Dec 2011 · Journal of Physics Conference Series
[Show abstract][Hide abstract] ABSTRACT: Clouds of ultra-cold atoms and especially Bose–Einstein condensates (BEC) provide a source for coherent matter-waves in numerous
earth bound experiments. Analogous to optical interferometry, matter-wave interferometers can be used for precision measurements
allowing for a sensitivity orders of magnitude above their optical counterparts. However, in some respects the presence of
gravitational forces in the lab limits experimental possibilities. In this article, we report about a compact and robust experiment
generating Bose–Einstein condensates in the drop tower facility in Bremen, Germany. We also present the progress of building
the succeeding experiment in which a two species atom interferometer will be implemented to test the weak equivalence principle
with quantum matter.
KeywordsBEC–Atom interferometry–Inertial Sensors–Microgravity–Equivalence principle
No preview · Article · Jun 2011 · Microgravity - Science and Technology
[Show abstract][Hide abstract] ABSTRACT: The generation of entanglement between two oscillators that interact via a
common reservoir is theoretically studied. The reservoir is modeled by a
one-dimensional harmonic crystal initially in thermal equilibrium. Starting
from a separable state, the oscillators can become entangled after a transient
time, that is of the order of the thermalization time scale. This behavior is
observed at finite temperature even when the oscillators are at a distance
significantly larger than the crystal's interparticle spacing. The underlying
physical mechanisms can be explained by the dynamical properties of the
collective variables of the two oscillators which may decouple from or be
squeezed by the reservoir. Our predictions can be tested with an ion chain in a
linear Paul trap.
Full-text · Article · Feb 2011 · EPL (Europhysics Letters)
[Show abstract][Hide abstract] ABSTRACT: In the present paper we follow three major themes: (i)concepts of rotation in general relativity, (ii)effects induced by
these generalized rotations, and (iii)their measurement using interferometry. Our journey takes us from the Foucault pendulum
via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel’s Universe. Throughout
our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose–Einstein condensates
leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent
matter wave interferometer in an extended free fall.
Preview · Article · Dec 2010 · Space Science Reviews
[Show abstract][Hide abstract] ABSTRACT: Albert Einstein’s insight that it is impossible to distinguish a local experiment in a “freely falling elevator” from one
in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a
striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic
wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during
free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter
wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test
the universality of free fall with quantum matter.
[Show abstract][Hide abstract] ABSTRACT: We show that in complete agreement with classical mechanics, the dynamics of
any quantum mechanical wave packet in a linear gravitational potential involves
the gravitational and the inertial mass only as their ratio. In contrast, the
spatial modulation of the corresponding energy wave function is determined by
the third root of the product of the two masses. Moreover, the discrete energy
spectrum of a particle constrained in its motion by a linear gravitational
potential and an infinitely steep wall depends on the inertial as well as the
gravitational mass with different fractional powers. This feature might open a
new avenue in quantum tests of the universality of free fall.
Full-text · Article · Jun 2010 · Applied Physics B
[Show abstract][Hide abstract] ABSTRACT: Atom interferometry represents a quantum leap in the technology for the ultra-precise monitoring of accelerations and rotations
and, therefore, for the science that relies on these quantities. These sensors evolved from a new kind of optics based on
matter-waves rather than light-waves and might result in an advancement of the fundamental detection limits by several orders
of magnitude. This paper describes the current status of the Space Atom Interferometer project (SAI), funded by the European
Space Agency. In a multi-pronged approach, SAI aims to investigate both experimentally and theoretically the various aspects
of placing atom interferometers in space: the equipment needs, the realistically expected performance limits and potential
scientific applications in a micro-gravity environment considering all aspects of quantum, relativistic and metrological sciences.
A drop-tower compatible atom interferometry acceleration sensor prototype has been designed, and the manufacturing of its
subsystems has been started. A compact modular laser system for cooling and trapping rubidium atoms has been assembled. A
compact Raman laser module, featuring outstandingly low phase noise, has been realized. Possible schemes to implement coherent
atomic sources in the atom interferometer have been experimentally demonstrated.
KeywordsAtom interferometry-Inertial sensors
Full-text · Article · Mar 2010 · Microgravity - Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Albert Einstein’s insight that it is impossible to distinguish a local experiment in a “freely falling elevator” from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein
condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality
of free fall with quantum matter.
[Show abstract][Hide abstract] ABSTRACT: Summary form only given. Bose Einstein condensates (BEC) opened the way for realization of atomic ensembles with Heisenberg limited uncertainty. In microgravity extremely dilute samples of BEC can be obtained and observed after a free evolution on timescales of seconds. Applications range from atom optics to matter wave interferometry. This has led us to realize a BEC of 10000 87Rb atoms in microgravity. The experimental results (to be published) establish the fact, that in a microgravity environment ultra-large condensates (Icircosl.5 mm) after a free evolution of 1 second can be observed. In particular, microgravity provides mass independent confining potential which is very important for the research on a mixture of quantum gases. We aim to realize a new setup for multispecies experiments, which can be used in catapult mode doubling the time for microgravity to 9 seconds. The experiment is planned to use <sup>87</sup>Rb and <sup>40</sup>K as degenerate Bose and Fermi gases respectively and can be used to carry out experiments on interferometry, Bose-Fermi mixtures and tests of the weak equivalence principle in quantum domain. Up to date progress and future prospects of this ambitious and technically challenging project will be presented.
[Show abstract][Hide abstract] ABSTRACT: We compare and contrast the different points of view of rotation in general
relativity, put forward by Mach, Thirring and Lense, and Goedel. Our analysis
relies on two tools: (i) the Sagnac effect which allows us to measure rotations
of a coordinate system or induced by the curvature of spacetime, and (ii)
computer visualizations which bring out the alien features of the Goedel
Universe. In order to keep the paper self-contained, we summarize in several
appendices crucial ingredients of the mathematical tools used in general
relativity. In this way, our lecture notes should be accessible to researchers
familiar with the basic elements of tensor calculus and general relativity.
Preview · Article · May 2009 · La Rivista del Nuovo Cimento
[Show abstract][Hide abstract] ABSTRACT: The weak Equivalence Principle (EP) represents a corner stone in the General Theory of relativity . The validity of this postulate was and is currently tested in different groups with different systems. Among this multitude atom interferometry is considered to be one of the most powerful tools in performing high-precision measurements . Using two atom species in free fall with different masses allows comparing two independent measurements of g. This is made possible by creating simultaneously in a single experiment a mixture of two atomic species at a temperature close to the absolute zero. This regime is suitable to the observation of matter waves at long time scales needed for quantum tests. In this letter an overview of the last developments of these quantum sensors is done. The up-to-date progress and future prospects in our group of these ambitious and technically challenging projects will be presented as well.
[Show abstract][Hide abstract] ABSTRACT: Low gravity provides an outstanding basis for precision measurements in atom optics pursuing multi-disciplines in fundamental physics. On the other hand it leads to an utilization of ultracold quantum matter techniques in unique practical applications. We report on the first establishments of atom optical experiments in the gravitation-free conditions at the Drop Tower Bremen in Germany, a facility of the Center of Applied Space Technology and Microgravity (ZARM). The chosen drop tower has an easy access to low gravity on earth with a daily usage, a more than sufficient time of free fall for experiments in quantum regimes (about 4s in drop mode and about 9s in catapult mode) and a well quality of weightlessness of 10-6g. Our report demonstrates the results of the precursor pilot project ATKAT ("atom catapult") and the current pilot project QUANTUS ("quantum systems under weightlesness") . The pure technological experiment ATKAT could successfully realize a compact and robust setup for trapping and cooling neutral rubidium atoms ( 87Rb) in microgravity conditions. After ATKAT's test accomplishment we have started the parallel developed QUANTUS main pilot projekt to investigate quantum degenerated gases in free fall. The first Bose-Einstein condensate (BEC) in a weightless environment world wide and longest evolution times of the 87Rb BEC up to 1s could be achieved within the science experiment QUANTUS. In respect thereof our collaboration opens further opportunities in atom optics. At least we will give an outlook of the new QUANTUS II project and its supporting project PRIMUS ("precision interferometry with matter waves under weightlessness") aiming on a precise inertial sensor by using an atom interferometer under weightlessness.
[Show abstract][Hide abstract] ABSTRACT: We experimentally demonstrate the possibility of preparing ultracold atoms in the environment of weightlessness at the earth-bound short-term microgravity laboratory Drop Tower Bremen, a facility of ZARM – University of Bremen. Our approach is based on a freely falling magneto-optical trap (MOT) drop tower experiment performed within the ATKAT collaboration (“Atom-Catapult”) as a preliminary part of the QUANTUS pilot project (“Quantum Systems in Weightlessness”) pursuing a Bose–Einstein condensate (BEC) in microgravity at the drop tower [1, 2].
Furthermore we give a complete account of the specific drop tower requirements to realize a compact and robust setup for trapping and cooling neutral rubidium 87Rb atoms in microgravity conditions. We also present the results of the first realized freely falling MOT and further accomplished experiments during several drops.
The goal of the preliminary ATKAT pilot project is to initiate a basis for extended atom-optical experiments which aim at realizing, observing and investigating ultracold quantum matter in microgravity.
Full-text · Article · Dec 2007 · Applied Physics B