Does an atom interferometer test the gravitational redshift at the Compton frequency ?

Atom interferometers allow the measurement of the acceleration of freely falling atoms with respect to an experimental platform at rest on Earth's surface. Such experiments have been used to test the universality of free fall by comparing the acceleration of the atoms to that of a classical freely falling object. In a recent paper, M\"uller, Peters and Chu [Nature {\bf 463}, 926-929 (2010)] argued that atom interferometers also provide a very accurate test of the gravitational redshift when considering the atom as a clock operating at the Compton frequency associated with the rest mass. We analyze this claim in the frame of general relativity and of different alternative theories. We show that the difference of "Compton phases" between the two paths of the interferometer is actually zero in a large class of theories, including general relativity, all metric theories of gravity, most non-metric theories and most theoretical frameworks used to interpret the violations of the equivalence principle. Therefore, in most plausible theoretical frameworks, there is no redshift effect and atom interferometers only test the universality of free fall. We also show that frameworks in which atom interferometers would test the redshift pose serious problems, such as (i) violation of the Schiff conjecture, (ii) violation of the Feynman path integral formulation of quantum mechanics and of the principle of least action for matter waves, (iii) violation of energy conservation, and more generally (iv) violation of the particle-wave duality in quantum mechanics. Standard quantum mechanics is no longer valid in such frameworks, so that a consistent interpretation of the experiment would require an alternative formulation of quantum mechanics. As such an alternative has not been proposed to date, we conclude that the interpretation of atom interferometers as testing the gravitational redshift is unsound.Comment: 26 pages. Modified version to appear in Classical and Quantum Gravit

Atom interferometry and the Einstein equivalence principle

The computation of the phase shift in a symmetric atom interferometer in the presence of a gravitational field is reviewed. The difference of action-phase integrals between the two paths of the interferometer is zero for any Lagrangian which is at most quadratic in position and velocity. We emphasize that in a large class of theories of gravity the atom interferometer permits a test of the weak version of the equivalence principle (or universality of free fall) by comparing the acceleration of atoms with that of ordinary bodies, but is insensitive to that aspect of the equivalence principle known as the gravitational redshift or universality of clock rates.Comment: 5 pages, to appear in the proceedings of the "46th Rencontres de Moriond and GPhyS Colloquium on Gravitational Waves and Experimental Gravity", la Thuile, March 20-27, 201

Appliance Management for Federated Cloud Environments

International audienceCloud infrastructures provide compelling features for scientific and engineering applications. Federated clouds additionally promise improved scalability via access to a larger pool of resources and improved service availability through geographically distributed redundant servers. Effective use of federated clouds requires the creation of portable appliances and consistent appliance management techniques. The StratusLab Marketplace, a platform-agnostic appliance registry, facilitates appliance management in a federated environment. This paper describes the Marketplace design goals, implementation, and security concerns. It also covers the planned improvements based on our experience of running this service in production for more than two years

Operation of Site Running StratusLab toolkit v1.0

This document reports on one of the significant project milestones concerning the operation of a cloud site running StratusLab's cloud distribution (or toolkit). It is currently running v0.3 of the StratusLab distribution-a beta release of the upcoming 1.0 production release. In particular it presents the WP5 reference cloud service, the evolution of the service up to Month 10 of the project, and the way this service has been exploited to date. A major milestone regarding the exploitation has been the deployment of the first virtualized production grid site running on the project's reference cloud service

Grid technology for biomedical applications

International audienceThe deployment of biomedical applications in a grid environment has started about three years ago in several European projects and national ini-tiatives. These applications have demonstrated that the grid paradigm was rele-vant to the needs of the biomedical community. They have also highlighted that this community had very specific requirements on middleware and needed fur-ther structuring in large collaborations in order to participate to the deployment of grid infrastructures in the coming years. In this paper, we propose several ar-eas where grid technology can today improve research and healthcare. A cru-cial issue is to maximize the cross fertilization among projects in the perspec-tive of an environment where data of medical interest can be stored and made easily available to the different actors of healthcare, the physicians, the health-care centres and administrations, and of course the citizens

Final Report on the Evaluation of StratusLab Products

Over the course of the project, the project's software releases have been evaluated against identified requirements and against the needs of real users. Most of the formal requirements have been satisfied, with work in the second year concentrating on extentions to commercial applications, multi-platform support and sandboxing. Feedback from applications running on the StratusLab cloud can be grouped into four broad categories: Ease of Use, Integration & Operation, Better Informaton Flow, and High-Level Services. These categories provide a broad roadmap for the evolution of the StratusLab cloud distribution past the end of the project

CYCLONE Unified Deployment and Management of Federated, Multi-Cloud Applications

Various Cloud layers have to work in concert in order to manage and deploy complex multi-cloud applications, executing sophisticated workflows for Cloud resource deployment, activation, adjustment, interaction, and monitoring. While there are ample solutions for managing individual Cloud aspects (e.g. network controllers, deployment tools, and application security software), there are no well-integrated suites for managing an entire multi cloud environment with multiple providers and deployment models. This paper presents the CYCLONE architecture that integrates a number of existing solutions to create an open, unified, holistic Cloud management platform for multi-cloud applications, tailored to the needs of research organizations and SMEs. It discusses major challenges in providing a network and security infrastructure for the Intercloud and concludes with the demonstration how the architecture is implemented in a real life bioinformatics use case

Final Report on StratusLab Adoption

The StratusLab cloud distribution has been adopted by users from a wide range of scientific disciplines: astrophysics, software engineering, machine learning, high- energy physics, meteorology, and bioinformatics. In addition, there has been commercial update of the distribution for a turnkey private cloud solution aimed at SMEs and a large public deployment by Atos within the Helix Nebula initiative. Both partner and non-partner institutes have used the StratusLab distribution to provide cloud services to their users

Testing the Gravitational Redshift with Atomic Gravimeters?

Atom interferometers allow the measurement of the acceleration of freely falling atoms with respect to an experimental platform at rest on Earth's surface. Such experiments have been used to test the universality of free fall by comparing the acceleration of the atoms to that of a classical freely falling object. In a recent paper, M\"uller, Peters and Chu [Nature {\bf 463}, 926-929 (2010)] argued that atom interferometers also provide a very accurate test of the gravitational redshift (or universality of clock rates). Considering the atom as a clock operating at the Compton frequency associated with the rest mass, they claimed that the interferometer measures the gravitational redshift between the atom-clocks in the two paths of the interferometer at different values of gravitational potentials. In the present paper we analyze this claim in the frame of general relativity and of different alternative theories, and conclude that the interpretation of atom interferometers as testing the gravitational redshift at the Compton frequency is unsound. The present work is a summary of our extensive paper [Wolf et al., arXiv:1012.1194, Class. Quant. Grav. 28, 145017, (2011)], to which the reader is referred for more details.Comment: Contribution to the proceedings of the joint European Time and Frequency Forum and IEEE Frequency Control Symposium, 2011. Summary of the extensive paper arXiv:1012.1194, Class. Quant. Grav. 28, 145017, (2011

Reply to the comment on: "Does an atom interferometer test the gravitational redshift at the Compton frequency?"

Hohensee, Chu, Peters and M\"uller have submitted a comment (arXiv:1112.6039 [gr-qc]) on our paper "Does an atom interferometer test the gravitational redshift at the Compton frequency?", Classical and Quantum Gravity 28, 145017 (2011), arXiv:1009.2485 [gr-qc]. Here we reply to this comment and show that the main result of our paper, namely that atom interferometric gravimeters do not test the gravitational redshift at the Compton frequency, remains valid.Comment: To appear in Classical and Quantum Gravit