##### Conference

#### Gravitational Waves Detection with Atom Interferometry

**Feb, 23 2009 - Feb, 24 2009**

The number of participants is limited to 50. The participation fee for the Workshop is 150 Euros including registration, coffee-breaks, lunches and the social dinner. The fee should be paid cash on arrival at the registration desk

**Organizers**

Guglielmo M. Tino, University of Firenze, Italy

Flavio Vetrano, University of Urbino, Italy

**Abstract**

The possibility of using atom interferometers to detect gravitational waves is attracting increasing interest as an alternative to other detectors. Several papers were published discussing theoretical and experimental aspects. Although the results show that dedicated technological developments are still needed to achieve the required sensitivity values which are beyond those presently available, new schemes for atom interferometers, beam splitters and high flux coherent atomic sources could lead to an increase in sensitivity and make atom interferometers competitive with other gravitational wave detectors. The Workshop on "Gravitational Waves Detection with Atom Interferometry" will bring together scientists interested in theoretical and experimental aspects, to discuss different points of view and possible experimental implementations in Earth laboratories and in space. The Workshop will consist of oral presentations and open discussions.

**Topics**

Topic areas will include:

* Theoretical approach for determining the influence of GWs on matter waves & matter wave interferometry

* Atom Optics and Interferometry

* Status of art of "standard" optical ground based interferometers and perspectives of space interferometers

* Status of art of atom interferometers

* Possible sensitivity of atom interferometers for GW detection and comparison with different detectors

* Noise sources, squeezed atom states, entangled atomic sources, large-momentum-transfer atomic beamsplitters

* Astrophysical sources of GW

* Hot Topics

**Preview**

The provisional list of speakers includes:

- Ch. J. BORDE (Laboratoire de physique des lasers, Université Paris-Nord and SYRTE)

- P. DELVA (European Space Agency, Advanced Concepts Team)

- W. ERTMER (Institute of Quantum Optics, Leibniz Universität Hannover)

- A. GIAZOTTO (INFN, Pisa)

- C. LAEMMERZAHL (ZARM, University of Bremen)

- H. MUELLER (UC Berkeley)

- A. PETERS (Humboldt-Universitaet zu Berlin)

- E. RASEL (Institute of Quantum Optics, Leibniz Universität Hannover)

- A. ROURA (Los Alamos National Laboratory)

- W. SCHLEICH (Institut für Quantenphysik, Universität Ulm)

- F. VETRANO (INFN-Firenze and University of Urbino)

- A. VICERE (INFN-Firenze and University of Urbino)

- S. VITALE (University of Trento)

- S. WHITCOMB (LIGO/Caltech)

- N. YU (Jet Propulsion Laboratory, California Institute of Technology)

**Talks**

Feb, 23 2009 - 10:10 | S. Whitcomb | Across the gravitational wave spectrum | Electromagnetic observations in astronomy span more than 21 orders of magnitude in frequency, with a range of different detectors and technologies. Detectable astrophysical gravitational waves might span nearly as wide a range, up to 15 orders of magnitude, and will require detector strategies tailored to each frequency regime. I will review some fundamental properties of gravitational waves, highlight the various sources that may contribute in different frequency regimes, and the currently favored detection techniques in each of those frequency regimes. At the end of this talk, I add a few personal observations about the tensions and interactions between established technologies in gravitational wave detection and new ones entering the field | Slides | |||

Feb, 23 2009 - 10:50 | A. Vicerè | The science potential of gravitational wave observation | We will briefly review the expected gravitational wave sources, discussing what we have already learned and what we will learn in the future from their observation. The role of the different classes of GW detectors will be outlined, including the possible contribution by atom interferometers. We will demonstrate how GW science requires a world network of instruments, and a close collaboration with neutrino and electro-magnetic detectors. | Slides | |||

Feb, 23 2009 - 11:50 | A. Giazotto | Status of gravitational waves detection and related topics | We will briefly review the expected gravitational wave sources, discussing what we have already learned and what we will learn in the future from their observation. The role of the different classes of GW detectors will be outlined, including the possible contribution by atom interferometers. We will demonstrate how GW science requires a world network of instruments, and a close collaboration with neutrino and electro-magnetic detectors. | Slides | |||

Feb, 23 2009 - 12:30 | V. Pustovoyt | Photons resonant tunneling | The problem of direct gravity waves detection exists more than half a century, but only now sensitivity of built-up gravity antennas is approaching such level, when we are expected to obtain the result of gravity radiation direct detection within the nearest several years. The increased interest to this problem is connected not so much with one more proof of theory of relativity as with the fact that creation of systems of gravity waves direct registration opens unique possibilities for astronomy and astrophysics, providing to trace the universe evolution at considerably larger spatial and time scales. Modern quite expensive experimental facilities being built is based on Michelson’s interferometer containing Fabry-Perot resonator in each leg. Mirrors, forming Fabry-Perot resonator, distance between which varies under the influence of gravity wave, are used as trial free-pendulous masses. The idea of such laser interferometer as a technique of gravity waves detection, was first suggested in the work by M.E. Gertsenstein and the author in 1962. Minimum detectable displacement of one mirror with respect to another, obtained by the present moment, is about 10-16 cm, however, for reliable direct experimental evidence of gravity waves existence it is necessary to increase sensitivity of such gravity antennas at six more orders. The problem of such systems sensitivity enhancement requires either further enlargement of interferometer legs (as it is suggested in the system space variant - LISA Project) or manufacturing mirrors with reflection factor differing from 100% not greater than 10-5. To increase reflection factor in modern laser interferometers, reflecting surfaces with quarter-wave-length layers numbering up to 45, are used. However, as it is shown in the present work, with the increase of number of reflecting surfaces, not only increase of reflection factor of laser reflection from periodic structure occurs, but also considerable variation of periodic struct | Slides | |||

Feb, 23 2009 - 14:15 | Ch. J. Bordé | Comparison of photon and atom interferometers using 5D optics | A wave equation written in five dimensions [1] reduces atom optics to 5D-optics of massless particles. This is a natural framework to unify and compare photon and atom optics. The ordinary methods of optics (Lagrange invariant, Fermat principle, symplectic algebra and ABCD matrices [2]....) are used to solve this equation in practical cases. The various phase shifts, which occur in interferometers, including the effect of gravitational waves [3], are then easily derived and will be discussed. | Slides | |||

Feb, 23 2009 - 14:55 | C. Laemmerzahl | Atom interferometry for testing gravity | We discuss various directions for testing relativity and gravity with atom interferometry. Beside the well known issues of testing the Equivalence Principle (for mass, spin, and charge) and Lorentz invariance we also cover possible tests of (i) modified dispersion relation, (ii) space-time fluctuations (including high frequency gravitational waves), (iii) Finsler geometry, (iv) non-linearity of quantum mechanics, (v) Newton's second law (law of reciprocal actions in terms of active and passive charges), and (vi) of Newton's second law (including MOND). | Slides | |||

Feb, 23 2009 - 16:00 | L. Lusanna | Towards relativistic atomic physics and post-minkowskian gravitational waves | The classical Hamiltonian basis of fully relativistic atomic physics, namely an isolated system of charged particles plus the transverse electro-magnetic field in the radiation gauge, with the explicit form of the Poincarè generators is reviewed. Its formulation in non-inertial Minkowski frames requires a gauge choice of the instantaneous 3-space, i.e. a convention for clock synchronization. As a consequence, the quantization induces a "kinematical non-locality" due to the Poincarè group: relativistic entanglement, with photons moving along null geodesics, is more complex of its non-relativistic counterpart, where only "quantum non-locality" is present. If also gravity is present and is described in the York canonican basis, the gauge freedom in the choice of the instntaneous 3-space gives rise to an "inertial" effect absent in Newtonian gravity and which could be relevant both in astrophysics (dark matter and dark energy) and in Post-Minkowskian gravity (gravitational waves). | Slides | |||

Feb, 23 2009 - 16:35 | E. Kajari | Sagnac effect in a proper reference frame | In view of the fascinating experimental progress concerning matter-wave interferometry in space, we would like to draw attention to the so-called proper reference frame coordinates which provide a suitable theoretical framework for the description of future satellite experiments. We apply these specific local coordinates to Sagnac interferometry with light and present the corresponding first two leading order contributions. We conclude by introducing a simple measurement scheme, which provides not only information about the rotation relative to the compass of inertia, but also about the spacetime curvature along the world line of the satellite | Slides | |||

Feb, 23 2009 - 17:10 | S. Vitale | Gravitational wave detection by macroscopic test-mass laser tracking: LISA, LISA Pathfinder and the fundamental limitations | Slides | ||||

Feb, 24 2009 - 09:00 | E. Rasel | Inertial atomic quantum sensors | Atom interferometers are more and more developing from laboratory prototypestowards inertial sensors with multi disciplinary applications on ground and in space. They represent a method for realising nearly ideal free falling inertial reference systems to measure inertial and gravitational forces with highest sensitivity and in particular with highest accuracy. On ground current state of the art inertial sensors, either of atomic or photonic nature, measure gravity with an accuracy of a few parts in 109. The demonstrated long term stabilities (at timescales of 103 to 104 s) for cold atom gyroscopes are 10‐8 rad/s. The ultimate limitations of these devices are still not known, new techniques and concepts are still emerging. Examples are atom lasers and other sources of degenerate quantum gases, where the potential for applications in high precision measurement is yet to be explored and are unanswered. High accuracy and long term stability are the most important features of these sensors and makes them interesting for space navigation and long term geodesy. Inertial atomic sensor combined with ultra stable clocks show a high potential to improve the current knowledge of the geoid by combining high accuracy gravitational red shift measurements, position measurements and local gravity measurements. | Slides | |||

Feb, 24 2009 - 09:30 | H. Mueller | Atom optics for gravitational wave detection | The sensitivity of atom interferometers is given by the atom optics used for splitting the matter waves. Detecting gravitational waves requires new atom optics that can increase the splitting of the interferometer arms by factors of 100s. Moreover, common-mode rejection between simultaneous interferometers is required. We have experimentally demonstrated large-area interferometers based on multiphoton Bragg diffraction of matter waves at an optical lattice. This allowed us to split the matter waves by 24 photon momenta, the largest splitting so far. Moreover, we have demonstrated the required common-mode rejection between simultaneous large-area atom interferometers. The rejection of vibrations thus afforded allowed us to increase the enclosed area by a factor of 2,500 for interferometers with 20 photon momentum splitting. Finally, we have demonstrated a “Bloch-Bragg-Bloch” (BBB) beam splitter, which has so far reached a splitting of up to 88 photons and interference with good contrast at 24 photons. It combines Bragg diffraction with accelerating sections of Bloch oscillations. Its momentum transfer is not limited by laser power and may reach 100s or even 1000s of photons. Using our measured data as a basis, we believe we can present a very strong case that gravitational wave detection with atom interferometry is realistic. | Slides | |||

Feb, 24 2009 - 10:00 | N. Yu | Space quantum science and technology at JPL | The presentation briefly describes the technology development activities at JPL. The activities include, atomic clocks and atom interferometers. | Slides | |||

Feb, 24 2009 - 11:00 | M. Buchner | Atom interferometry with separated paths | Atom interferometers are able to measure directly the phase shifts of the atom de Broglie waves resulting from various perturbations. To perform such a measurement, it is necessary to separate the atomic paths inside the interferometer and to apply the perturbation on only one path. In this way, several high sensitivity measurements have been made such as the complex refraction index of gases for matter waves or the electric polarizability of atoms. We have recently measured the van der Waals atom- surface interaction due to the traversal of a nanograting and we have achieved a large phase sensitivity, near 1 milliradians. These separated path interferometers are based on the Mach-Zehnder geometry and the coherent manipulation of the wave is made by diffraction, using either nanogratings or elastic Bragg diffraction by near-resonant laser standing waves. These interferometers can also achieve a large sensitivity to inertial effects but, up-to-now, they have not been practically used for such measurements because they have been operated with thermal atoms: the sensitivity to rotation (respectively to acceleration) which scales like the time T spent by the atoms in the interferometer (respectively T2) was not large enough to be competitive with existing atom interferometers devoted to the measurement of rotation. This will be possible if we use a slow atomic beam but this modification requires at the same time an efficient control of the seismic vibrations. These vibrations induce, through Sagnac effect, an important phase noise, which reduces the fringe visibility and this reduction will increas e when the atom velocity is reduced. We are presently developing a new interferometer involving an atomic beam slowed and intensified by laser and a support for the mirror of the laser standing waves with an active suspension to reduce the seismic noise by a large factor. The use of a slow atomic beam will enhance by a large factor the sensitivity to rotation and the us | Slides | |||

Feb, 24 2009 - 11:30 | X. Lu | Atom interferometer’s potential application for the gravitational waves detection | At present, atom interferometer has been paid attention for its ultra high precision and the widely applications, such as the gravity measurement [1], rotating gyroscope [2], checking the equivalent principle [3], gravitational waves detection etc. However, our lab is building an atom interferometer, which is proposed to measure the gravity field accurately. Its present sensitivity values are not yet reaching required sensitivity values for the gravitational waves detection. We are searching for improving the method for detection sensitivity. | Slides | |||

Feb, 24 2009 - 12:00 | G. Stern | Towards compact transportable atom interferometric inertial sensors | Atom-interferometric inertial sensors rival in accuracy and precision state-of-the-art conventional sensors. Moreover, the quantity they measure directly relates to inertial effects on well-controlled weakly-interacting Dirac particles, and is thus of interest for tests of gravitational theories. Their current precision is limited by the scaling factor of the interferometer, scaling up with the available atomic free-fall time, and technical noise, mainly due to vibrations of apparatus. We present progress on transportable atom-interferometry apparatuses that can be used on ground or in ballistic flights to perform measurements in microgravity. A novel laser source using standard fibered telecom components and frequency doubling to rubidium wavelength (780nm) allows for compact and transportable laser sources suitable for laser cooling and coherent manipulation of atoms in a noisy environment. A cold-atom apparatus for coherent-splitting of laser-cooled rubidium clouds has been been tested to produce a magneto-optical trap and interference fringes during a flight campaign. We also present the use of telecoms wavelenght to produce coherent samples of atoms with duty cycles that can approach 1Hz. This coherent atomic source has been used to test an original design of accelerometer where the atoms oscillate freely in a gravitational cavity. | Slides | |||

Feb, 24 2009 - 12:30 | A. Peters | Atom interferometry – applications in gravimetry and some thoughts on current sensitivity limitations and concepts for future improvements | Slides | ||||

Feb, 24 2009 - 14:15 | F. Vetrano | Atom interferometers for gravitational wave detection: a look at a "simple" configuration | The frequency response function to GWs of a atom interferometer with Mach-Zehnder configuration is evaluated, assuming all the beam-splitting operations obtained through light field. The calculation uses the method of ABCD matrices for wave packets, taking into account different descriptions (i.e. different coordinate systems). Starting from a naive definition of the actual Shot Noise (SN), some SN-limited sensitivity curves are derived and discussed in short | Slides | |||

Feb, 24 2009 - 14:45 | P. Delva | The sensitivity of atom interferometers to gravitational waves | In this talk we present the calculation of the sensitivity of atom interferometers to gravitational wave. We compare it to ground-based interferometers such as Virgo and planned spaced-based interferometers such as LISA. We will outline the present difficulties in order to obtain a comparable sensitivity. In the recent literature, there have been several derivation of the phase difference of an atom interferometer due to a gravitational wave. We discuss these derivations, and in particular discuss the physical meaning of the Fermi frame. | Slides | |||

Feb, 24 2009 - 15:45 | D. Lorek | Rovibrational quantum interferometers and gravitational waves | We show that the application of atom interferometry techniques to the internal, i.e. rotational-vibrational states of molecules provides a new tool for ultra-high precision tests of fundamental physics. As an example we present how a molecular rovibrational quantum interferometer based on the HD+ molecule may be used to detect gravitational waves. The perturbation of the molecular Hamiltonian by a gravitational wave is derived, the quantum interferometric measurement principle is described, and the size of the effect is estimated. | Slides | |||

Feb, 24 2009 - 16:15 | A. Roura | Atom vs. laser interferometers for gravitational-wave detection | The detection of gravitational waves (GWs) will open a completely new window for observing the universe with deep implications for astrophysics and cosmology. However, it will require detectors with unprecedented sensitivity. This quest is currently led by several kilometer-size laser interferometers around the world. On the other hand, atom interferometers are being used to measure gravitational properties with increasing precision, and several schemes based on atom interferometry have been proposed to achieve sensitivities competitive with those of gravitational-wave detectors employing laser interferometers. I will present a careful theoretical analysis of the response to GWs for these kind of atom interferometers and provide a critical comparison of their performance with that of laser interferometers. Finally, I will conclude by discussing possible future directions in the field. | Slides |