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"Gravitational Waves Detection with Atom Interferometry", Firenze, February 2324, 2009 International Workshop on "Gravitational Waves Detection with Atom Interferometry" February 2324, 2009 Galileo Galilei Institute for Theoretical Physics (GGI)  Arcetri, Firenze (Italy) PROGRAM Day 1  Monday, 23 February 2009 9.00  10.00 Registration Morning Session: Chair: Guglielmo Tino 10.00  10.10 Welcome 10.1010.50 S. Whitcomb (LIGO/Caltech, Pasadena, USA) Across the gravitational wave spectrum 10.50 – 11.25 A. Vicerè (INFNFirenze and University of Urbino, Italy) The science potential of gravitational wave observation 11.25 – 11.50 Coffee break Chair: Andrea Viceré 11.5012.30 A. Giazotto (INFN, Pisa, Italy) Status of gravitational waves detection and related topics 12.3013.00 V. Pustovoyt (Russian Academy of Sciences, Moscow, Russia) Photons resonant tunneling 13.00 – 14.15 Lunch Afternoon Session: Chair: Luca Lusanna 14.15  14.55 Ch. J. Bordé (Université ParisNord and SYRTE, Paris, France) Comparison of photon and atom interferometers using 5D optics 14.55 – 15.35 C. Laemmerzahl (ZARM, University of Bremen, D) Atom interferometry for testing gravity 15.35 – 16.00 Coffee break Chair: Adalberto Giazotto 16.0016.35 L. Lusanna (INFN, Firenze, Italy) Towards relativistic atomic physics and postminkowskian gravitational waves 16.3517.10 E. Kajari (Institut für Quantenphysik, Universität, Ulm, D) Sagnac effect in a proper reference frame 17.1017.45 S. Vitale (University of Trento, Trento, Italy) Gravitational wave detection by macroscopic testmass laser tracking: LISA, LISA Pathfinder and the fundamental limitations Social Dinner  Day 2  Tuesday, 24 February 2009 Morning Session: Chair: Francesco Ronga 9.009.30 E. Rasel (Institute of Quantum Optics, Leibniz Universität, Hannover, D) Inertial atomic quantum sensors 9.3010.00 H. Mueller (UC Berkeley, Berkeley, USA), Atom optics for gravitational wave detection 10.0010.30 N. Yu (Jet Propulsion Laboratory, Pasadena, USA) Space quantum science and technology at JPL 10.3011.00 Coffee break Chair: Stan Whitcomb 11.0011.30 M. Buchner (Université Paul Sabatier, Toulouse, France) Atom interferometry with separated paths 11.3012.00 X. Lu (Zhejiang University, Hangzhou, China), Atom interferometer’s potential application for the gravitational waves detection 12.0012.30 G. Stern (LCFIOSYRTE, Palaiseau, France) Towards compact transportable atom interferometric inertial sensors 12.3013.00 A. Peters (HumboldtUniversitaet zu Berlin, D) Atom interferometry – applications in gravimetry and some thoughts on current sensitivity limitations and concepts for future improvements 13.00  14.15 Lunch Afternoon Session: Chair: TBD 14.1514.45 F. Vetrano (INFNFirenze and University of Urbino, Italy) Atom interferometers for gravitational wave detection: a look at a "simple" configuration 14.4515.15 P. Delva (European Space Agency, Advanced Concept Team) The sensitivity of atom interferometers to gravitational waves 15.1515.45 Coffee Break Chair: Flavio Vetrano 15.4516.15 D. Lorek (Center of Applied Space Technology and Microgravity, Bremen, D) Rovibrational quantum interferometers and gravitational waves 16.1516.45 A. Roura (Los Alamos National Laboratory, Los Alamos, USA) Atom vs. laser interferometers for gravitationalwave detection LIST OF ABSTRACTS Across the gravitational wave spectrum S. Whitcomb (LIGO/Caltech, Pasadena, USA) 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. The science potential of gravitational wave observation
(INFNFirenze and University of Urbino, Italy) 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 electromagnetic detectors. Status of gravitational waves detection and related topics
(INFN, Pisa, Italy) The status of gravitational wave detection together with recent advances in optical noises reduction are presented. Problems connected with gravitational wave first detection are presented and discussed too Photons resonant tunneling V. Pustovoyt (Russian Academy of Sciences, Moscow, Russia) The problem of direct gravity waves detection exists more than half a century, but only now sensitivity of builtup 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 FabryPerot resonator in each leg. Mirrors, forming FabryPerot resonator, distance between which varies under the influence of gravity wave, are used as trial freependulous 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 1016 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 105. To increase reflection factor in modern laser interferometers, reflecting surfaces with quarterwavelength 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 structure transfer function, and appearance of exponentially narrow bandpasses (much narrower than in standard Michelson’s interferometer). Essentially, it is a classic counterpart of famous quantum effect of particles resonant tunneling through two barriers, which takes place when a particle energy corresponds to energy level in interbarriers region. All this allows to suggest new gravity antennas for gravity waves detection, based on MachZehnder interferometer, which possess considerably higher sensitivity. Comparison of photon and atom interferometers using 5D optics Ch. J. Bordé (Université ParisNord and SYRTE, Paris, France) A wave equation written in five dimensions [1] reduces atom optics to 5Doptics 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. Atom interferometry for testing gravity C. Laemmerzahl (ZARM, University of Bremen, D) 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) spacetime fluctuations (including high frequency gravitational waves), (iii) Finsler geometry, (iv) nonlinearity 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). Towards relativistic atomic physics and postminkowskian gravitational waves L. Lusanna (INFN, Firenze, Italy) The classical Hamiltonian basis of fully relativistic atomic physics, namely an isolated system of charged particles plus the transverse electromagnetic field in the radiation gauge, with the explicit form of the Poincare' generators is reviewed. Its formulation in noninertial Minkowski frames requires a gauge choice of the instantaneous 3space, i.e. a convention for clock synchronization. As a consequence, the quantization induces a "kinematical nonlocality" due to the Poincare' group: relativistic entanglement, with photons moving along null geodesics, is more complex of its nonrelativistic counterpart, where only "quantum nonlocality" is present. If also gravity is present and is described in the York canonican basis, the gauge freedom in the choice of the instntaneous 3space 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 PostMinkowskian gravity (gravitational waves). Sagnac effect in a proper reference frame E. Kajari (Institut für Quantenphysik, Universität, Ulm, D) In view of the fascinating experimental progress concerning matterwave interferometry in space, we would like to draw attention to the socalled 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. Gravitational wave detection by macroscopic testmass laser tracking: LISA, LISA Pathfinder and the fundamental limitations S. Vitale (University of Trento, Trento, Italy) Inertial atomic quantum sensors E. Rasel (Institute of Quantum Optics, Leibniz Universität, Hannover, D) 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. Atom optics for gravitational wave detection H. Mueller (UC Berkeley, Berkeley, USA) 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, commonmode rejection between simultaneous interferometers is required. We have experimentally demonstrated largearea 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 commonmode rejection between simultaneous largearea 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 “BlochBraggBloch” (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. Space quantum science and technology at JPL N. Yu (Jet Propulsion Laboratory, Pasadena, USA) The presentation briefly describes the technology development activities at JPL. The activities include, atomic clocks and atom interferometers. Atom interferometry with separated paths M. Buchner (Université Paul Sabatier, Toulouse, France) 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 MachZehnder geometry and the coherent manipulation of the wave is made by diffraction, using either nanogratings or elastic Bragg diffraction by nearresonant laser standing waves. These interferometers can also achieve a large sensitivity to inertial effects but, uptonow, 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 use of higher diffraction orders, which has been demonstrated by various groups, will further enhance this sensitivity. In the talk, we will present our measurement of the van der Waals atom surface interaction and we will discuss the main features of our new atom interferometer presently under construction and its expected sensitivity to rotation. Atom interferometer’s potential application for the gravitational waves detection X. Lu (Zhejiang University, Hangzhou, China) 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. Towards compact transportable atom interferometric inertial sensors G. Stern (LCFIOSYRTE, Palaiseau, France) Atominterferometric inertial sensors rival in accuracy and precision stateoftheart conventional sensors. Moreover, the quantity they measure directly relates to inertial effects on wellcontrolled weaklyinteracting 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 freefall time, and technical noise, mainly due to vibrations of apparatus. We present progress on transportable atominterferometry 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 coldatom apparatus for coherentsplitting of lasercooled rubidium clouds has been been tested to produce a magnetooptical 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. Atom interferometry – applications in gravimetry and some thoughts on current sensitivity limitations and concepts for future improvements
(HumboldtUniversitaet zu Berlin, D) Atom interferometers for gravitational wave detection: a look at a "simple" configuration F. Vetrano (INFNFirenze and University of Urbino, Italy) The frequency response function to GWs of a atom interferometer with MachZehnder configuration is evaluated, assuming all the beamsplitting 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 SNlimited sensitivity curves are derived and discussed in short. The sensitivity of atom interferometers to gravitational waves P. Delva (European Space Agency, Advanced Concept Team) In this talk we present the calculation of the sensitivity of atom interferometers to gravitational wave. We compare it to groundbased interferometers such as Virgo and planned spacedbased 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. Rovibrational quantum interferometers and gravitational waves D. Lorek (Center of Applied Space Technology and Microgravity, Bremen, D) We show that the application of atom interferometry techniques to the internal, i.e. rotationalvibrational states of molecules provides a new tool for ultrahigh 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. Atom vs. laser interferometers for gravitationalwave detection
(Los Alamos National Laboratory, Los Alamos, USA) 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 kilometersize 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 gravitationalwave 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. 