iCal export
I have read and understood the above.
I have read and understood the above.
Download current event:
Event calendar file
In order to enable an iCal export link, your account needs to have a key created. This key enables other applications to access data from within Indico even when you are neither using nor logged into the Indico system yourself with the link provided. Once created, you can manage your key at any time by going to 'My Profile' and looking under the tab entitled 'HTTP API'. Further information about HTTP API keys can be found in the Indico documentation.
In conjunction with a having a key associated with your account, to have the possibility of exporting private event information necessitates the creation of a persistent key. This new key is also associated with your account and whilst it is active the data which can be obtained through using this key can be obtained by anyone in possession of the link provided. Due to this reason, it is extremely important that you keep links generated with this key private and for your use only. If you think someone else may have acquired access to a link using this key in the future, you must immediately remove it from 'My Profile' under the 'HTTP API' tab and generate a new key before regenerating iCalendar links.
Permanent link for public information only:
Permanent link for all public and protected information:
Please use CTRL + C to copy this URL
Detailed timetable
More
Fundamental Problems in Quantum Physics
chaired by Angelo Bassi (TS), Catalina Oana Curceanu (LNF), Detlef Duerr (Mathematisches Institut LMU)
from
to
(Europe/Rome)
at Erice (Sicily)  Italy
at Erice (Sicily)  Italy
Description 
This is the final meeting of the COST Action "Fundamental Problems in Quantum Physics"
The conference will present a critical perspective of theoretical and experimental research in quantum physics: where are with at, with our understanding of the quantum world? What did we learn so far, and what are the most relevant open issues?
The topics addressed by the conference include:  Quantum Foundations  Mathematical Physics & QFT  Quantum Interferometry  Testing fundamental principles  Quantum complex systems  Quantum gravity  Gravity and Cosmology Within the Workshop a special event will be organized in honor of GianCarlo Ghirardi to celebrate his 80s birthday.


Support  donatella.pierluigi@lnf.infn.it 
Go to day


09:30  13:00
Quantum interferometry

09:30
Exploring the limits and applications of the quantum superposition principle: An introduction to matter wave interferometry with atoms, (bio)molecules and nanoparticles
45'
This talk introduces concepts and technologies in quantum interference experiments with massive particles, ranging from atoms and complex molecules today to dielectric nanoparticles in the future. Our work is motivated by the insight that the quantum superposition principle is at the heart of all quantum physics but that matter wave interference has not yet been tested experimentally in the regime of high masses. There is good reason to believe that established physics will persist in all regimes. But there is equally good reason to believe that the opposite is true. We will introduce the basic concepts of matterwave physics with reference to modern atom interferometry and discuss how to extrapolate these achievements to objects of substantially higher mass and complexity. This comprises challenges regarding advanced molecular beam sources, coherence preparation, particle detection and avoidance of decoherence. We will focus on advanced nanomechanical and optical beam splitting technologies as well as the development of novel sources for nanoparticles in the mass range of 10^710^8 amu. In this mass range it will be important to consider additional phase averaging and decoherence, as well as the possibility of consequences of continuous spontaneous localization models.
Speaker: Markus Arndt (University of Vienna) Material: Slides 
10:15
Pulsed matterwave interferometry for testing the mass limits of quantum mechanics
45'
We demonstrate a matterwave interferometer in the time domain (OTIMA) as a powerful tool for testing the validity of quantum theory for large particles [1,2]. The interferometer operates in the nearfield regime and utilizes three pulsed standing laser wave gratings. These imprint a periodic phase pattern on to the traversing matter waves and the photo depletion probability is modulated periodically with the distance from the reflecting mirror. Depending on the particle’s ionization or fragmentation cross section and their optical polarizability the gratings thus act as absorptive masks and phase gratings with an exceptionally small grating period of less than 80nm [3,4]. The pulsed experimental scheme facilitates interference measurements in the time domain which offers high count rate, visibility and measuring precision [3]. Since the action of pulsed optical gratings is nondispersive the experiment is well suited for interference experiments on an increasingly large mass scale in the quest for novel decoherence effects, such as continuous spontaneous localization [4]. Additionally, the ability to resolve fringe shifts as small as a fraction of the grating period opens up to measuring optical and electrical nanoparticle properties in the OTIMA interferometer with time domain enhanced precision [6]. Experiments with various organic clusters and monomers have demonstrated the functionality of the interferometer and serve as a motivation for exploring the waveparticle character of particles with masses up to 105 amu and beyond. References [1] N. Dörre, J. Rodewald, P. Geyer, B. von Issendorff, P. Haslinger, and M. Arndt, Phys. Rev. Lett. 113, 233001 (2014). [2] N. Dörre, P. Haslinger, J. Rodewald, P. Geyer, and M. Arndt, J. Opt. Soc. Am. B 32, 114 (2014). [3] S. Nimmrichter, P. Haslinger, K. Hornberger, and M. Arndt, New J. Phys. 13, 75002 (2011). [4] S. Nimmrichter, K. Hornberger, P. Haslinger, and M. Arndt, Phys. Rev. A 83, 43621 (2011). [5] S. Eibenberger, X. Cheng, J. P. Cotter, and M. Arndt, Phys. Rev. Lett. 112, 250402 (2014).
Speaker: Jonas Rodewald (University of Vienna) Material: Slides  11:00 Coffe Break 30'

11:30
Talbot interferometry with a pointlike source: rationale, technology, & experiment
45'
We are building a matterwave interferometer for 10^6 amu particles with 200 nm separation to test the superposition principle for massive particles [1] . A successful demonstration would correspond to a macroscopicity [2] mu=18 and would begin to constrain CSL lambda_CSL<1.4 · 10^r 11 Hz. I will outline the theoretical approach, describe the rationale for our design choices, and review the experimental progress so far. For particles in freeflight, our target mass appears to be a practical maximum for earthbound experiments; I will briefly mention the MAQRO consortium which seeks to put an experiment like ours into space [3] References [1] Bateman, Nimmrichter, Hornberger, Ulbricht, Nat. Comm. 5, 4788 (2014) [2] Nimmrichter & Hornberger, Phys. Rev. Lett. 110,160403 (2013) [3] Kaltenbaek et al., Exp. Astro. 34, 123 (2012).
Speaker: James Bateman (University of Southampton) Material: Slides 
12:15
Quantum Walks Disprove Theories Based on Classical Trajectories
45'
We report on a stringent test of the nonclassicality of the motion of a massive quantum particle, which propagates on a discrete lattice. Measuring temporal correlations of the position of single atoms performing a quantum walk, we observe a 6σ violation of the LeggettGarg inequality. Our results rigorously excludes (i.e., falsifies) any explanation of quantum transport based on classical, welldefined trajectories. We use socalled ideal negative measurements—an essential requisite for any genuine LeggettGarg test—to acquire information about the atom’s position, yet avoiding any direct interaction with it. Reference C. Robens, W. Alt, D. Meschede, C. Emary, and A. Alberti, Ideal Negative Measurements in Quantum Walks Disprove Theories Based on Classical Trajectories, Phys. Rev. X 5, 011003 (2015).
Speaker: Andrea Alberti (University of Bonn) Material: Slides

09:30
Exploring the limits and applications of the quantum superposition principle: An introduction to matter wave interferometry with atoms, (bio)molecules and nanoparticles
45'
 13:00  14:30 Lunch

14:30  18:00
Mathematical Physics & QFT

14:30
FermiPastaUlam chains and their approach to thermal equilibrium
45'
In 1953 Fermi, Pasta, and Ulam, technically supported by Tsingou, run pioneering numerical simulations on nonlinearly coupled oscillators. They wanted to test whether for long times the statistics is well described by the microcanonical ensemble, in particular confirm equipartition of energy. (The numerical findings were not too encouraging). In my talk, I will explain our current understanding of the issue raised by FPU.
Speaker: Herbert Spohn (TU Munich) Material: Slides 
15:15
Invariant Gibbs measures for Hamiltonian PDEs
45'
In the this talk, we discuss the construction and related problems of the invariant Gibbs measures for Hamiltonian PDEs. We briefly go over the construction of the invariant Gibbs measures on the circle due to Bourgain '94. Then, we will describe the construction on the real line, concentrating on the defocusing nonlinear Schroedinger equation.
Speaker: Tadahiro Oh (University of Edinburg) Material: Slides  16:00 Coffee Break 30'

16:30
Dirac's Class Two problems and recent developments in external field QED
45'
To date classical and quantum electrodynamics is missing a welldefined equation of motion. I will give a brief overview of the main obstacles and report on recent developments to overcome one of those in the model of external field QED. In particular, I will discuss how an evolution for the Dirac sea subject to an external electromagnetic fourpotential can be constructed that is free of singularities.
Speaker: Dirk Deckert (LMU Munich) Material: Slides 
17:15
Effective dynamics of a tracerparticle coupled to the ideal Fermi gas in the highdensity limit
20'
A tracerparticle coupled to the ideal Fermi gas in two spatial dimensions is considered. We prove that the time evolution of the system converges to the free dynamics in the highdensity limit. Eventually, we explain why this can be understood in the sense of a mean field result despite the absence of a weak coupling parameter.
Speaker: David Mitrouskas (LMU Munich) 
17:35
Quantum jumps and spikes
20'
Quantum systems subjected to a continuous monitoring can be described by a diffusive stochastic differential equation. However, in the limit where the measurement rate becomes large, the system evolution starts to be effectively discontinuous with Poisson like jumps between the eigenvectors of the measure. The limiting regime can be precisely described and the transition rates computed. However, the transition to the jumpy regime is not trivial and power law fluctuations that we have called "quantum spikes" subsist in the limit. The objective of this short talk is to explain this phenomenon. If time permits, I will discuss the link with a classical toy model for measurement and I will briefly hint at the possible foundationnal applications of quantum spikes to collapse models.
Speaker: Antoine Tilloy (Laboratoire de Physique Théorique, Ecole Normale Supérieure) Material: Slides

14:30
FermiPastaUlam chains and their approach to thermal equilibrium
45'

09:30  13:00
Quantum interferometry


09:30  13:00
Testing fundamental principles

09:30
Testing the properties of the QED vacuum, a review.
45'
In this talk I will review past and current experiments on the QED vacuum. The fluctuations of QFT vacuum are one of the hallmarks of field theory, and they carry with them a host of important implications. Photonphoton scattering  in all its incarnations  is a powerful tool to study these fluctuations in QED. Moreover, interactions of photons with yettobe detected pseudoscalar particles can provide precious hints of physics beyond the Standard Model, and lead to interesting reflections on the quantum nature of light.
Speaker: Edoardo Milotti (University of Trieste) Material: Slides 
10:15
Pauli Exclusion Principle tested with VIP2  J. Marton for the VIP2 Collaboration
45'
The Pauli Exclusion Principle (PEP) is one of the most fundamental pillars of physics and it has tremendous consequences  from the stability of matter to atomic and subatomic systems. According to many observations PEP must be valid to an extremely high degree and no violations were found up to now. On the other hand a simple explanation of PEP is missing. Numerous experimental investigations were performed to search for a tiny violation in different systems. The experiment VIP2 at the Gran Sasso underground laboratory is designed to test the PEP for electrons with high sensitivity by searching for forbidden Xray transitions in copper atoms. VIP2 aims to improve the PEP violation limit obtained with our preceding experiment VIP by orders of magnitude. The experimental method, comparison of different PEP tests based on different assumptions and the developments for the VIP2 setup will be presented.
Speaker: Johann Marton (Stefan Mayer Institute, Vienna) Material: Slides  11:00 Coffee Break 30'

11:30
Weak interactions: What foundational lessons can be learnt?
45'
Four (known) forces are ruling our Universe; the weak interaction is the only one violating discrete symmetries. This talk presents a surprising relation between the violation of such symmetries and various foundational concepts of quantum mechanics for spinless (mesons) and spin particles (hyperons). These systems show also an unexpected and puzzling relation to another big open question: Why is our Universe dominated by matter, why did the antimatter slip off the map?
Speaker: Beatrix Hiesmayr (University of Vienna) 
12:15
A new upper bound on collapse models parameters from spontaneous radiation emission.
45'
Collapse models are phenomenological models where the collapse of the wave function is described through a non linear interaction with an external classic noise. Because of the interaction with this noise, collapse models make different predictions compared to Quantum Mechanics. In the Continuous Spontaneous Localization (CSL) collapse model, the strength of the noise effects is measured by the collapse rate lambda. Nowadays, the best upper bound on lambda comes from the study of the spontaneous radiation emission from Germanium. In the first part of the talk we review the calculation of the spontaneous radiation emission in the CSL model. In particular, we discuss about some problems which arise when perturbation theory is applied to the lowest perturbative order. In the second part of the talk we compare this theoretical prediction with new experimental data. As a result, the current upper bound on lambda is improved by a few orders of magnitude.
Speakers: Kristian Piscicchia (LNFFrascati), Sandro Donadi (University of Trieste) Material: Slides

09:30
Testing the properties of the QED vacuum, a review.
45'
 13:00  14:30 Lunch

14:30  18:00
Quantum foundations

14:30
Quantum Physics without Quantum Philosophy
45'
Quantum philosophy, a peculiar twentieth century malady, is responsible for most of the conceptual muddle plaguing the foundations of quantum physics. When this philosophy is eschewed, one naturally arrives at Bohmian mechanics, which is what emerges from Schro ̈dinger’s equation for a nonrelativistic system of particles when we merely insist that “particles” means particles.
Speaker: Nino Zanghi (University of Genova) Material: Slides 
15:15
Collapse models, the quantumclassical transition, and experimental searches
45'
Physics at the quantumclassical border is one of the crucial fields of today’s research, both theoretical and experimental. One of the challenging questions is to understand if, and under which conditions, quantum linearity fails when the size and complexity of the system increases [1,2]. The exploration of this question has substantial consequences because if the quantum superposition principle fails beyond a certain scale (e.g., a mass scale), then it necessitates the modification of quantum theory (which may even result in a better scenario for unifying quantum theory with gravity [3]). Collapse models are one possible way among many, to modify the standard quantum theory in a fullyconsistent way [1]. Collapse model assumes a universal noise field that, when acting on matter, introduces nonlinear effects on the dynamics, which explains the collapse of the wave function. In other words, one can derive the random localization of the wave function at the end of a measurement, of course with the correct quantum probabilities. The strength of the collapse process scales with the size of the system, thus the wave function of microscopic systems can be superimposed, while macroscopic objects are always welllocalized [1]. Recently, there has been rapid experimental progress in revealing quantum features such as particlewave duality for large objects with tiny de Broglie wavelength of only a few hundred femtometer [4]. This progress provides the possibility to search for tests of collapse models. In this regard, quite a few new experimental schemes have been proposed. Most proposals are based on the natural idea of creating a macroscopic quantum superposition in space, in order to test the superposition principle. Creating macroscopic superpositions is very difficult, source of formidable technological challenges. We propose an alternative approach by measuring the fluctuating properties of light interacting with a system (e.g., a molecule or an optomechanical oscillator) [5]. Here, the collapse manifests as an extra broadening and shift in the spectral density. The most important advantageous of this new approach is that here there is no need for the preparation of a quantum superposed state. We speculated that the corresponding experimental realization is well within reach. References: [1] A. Bassi and G. C. Ghirardi, Phys. Rep. 379, 257 (2003). A. Bassi, K. Lochan, S. Satin, T. P. Singh, and H. Ulbricht, Rev. Mod. Phys. 85, 471 (2013). [2] M. Arndt and K. Hornberger, Nat. Phys. 10, 271 (2014). [3] R. Penrose, Found. Phys. 44, 557 ( 2014) [4] T. Juffmann, H. Ulbricht, M. Arndt, Reports on Progress in Physics 76 (8), 086402 (2013). [5] M. Bahrami, A. Bassi, and H. Ulbricht, Phys. Rev. A 89, 032127 (2014). M. Bahrami, M. Paternostro, A. Bassi, and H. Ulbricht, Phys. Rev. Lett. 112, 210404 (2014).
Speaker: Mohammad Bahrami (University of Trieste) Material: Slides  16:00 Coffee Break 30'

16:30
Wave Functions on SpaceTime
45'
In nonrelativistic quantum mechanics, a wave function depends on one time variable. A suitable relativistic generalization is a wave function that depends on a separate time variable for each particle, i.e., for N particles, it depends on N spacetime points. Such a function is called a multitime wave function. The study of these wave functions and their evolution equations is interesting from many perspectives, e.g., from a nonrigorous formal perspective as well as from a rigorous mathematical physics one. It is furthermore relevant for "standard" quantum (field) theory (i.e., on the level of wave functions, operators and quantum fields), as well as for the foundations of quantum mechanics, e.g., for Bohmian Mechanics, GRW and many worlds. In this talk I present an overview of the recent work of R. Tumulka and myself on the subject. The main questions I discuss are how and what kind of interaction can be implemented in the framework of multitime wave functions and how these wave functions are related to quantum field theory and the TomonagaSchwinger approach.
Speaker: Sören Petrat (IST  Vienna) Material: Slides 
17:15
Dissipative models of spontaneous wavefunction collapse
45'
Collapse models explain the absence of quantum superpositions at the macroscopic scale, while giving practically the same predictions as quantum mechanics for microscopic systems [1,2,3]. A wellknown problem of the original models is the steady and unlimited increase of the energy induced by the collapse noise. In this talk, I discuss two recently introduced collapse models [4,5], which guarantee a finite energy during the entire system's evolution, while preserving the specific features any collapse model must have. The first model is a generalization of the GhirardiRiminiWeber model [2,4]: here, the wavefunction undergoes instantaneous localization processes, distributed in time according to a Poisson process. In the second model [3,5], which also applies to identical particles, the collapse noise modifies continuously the wavefunction, inducing a diffusive localization process. We define new localization operators, which depend on the momentum of the system and thus introduce dissipation in the dynamics, leading to an exponential relaxation of the energy to a finite value. Such a finite value is naturally associated with a finite temperature of the collapse noise and, remarkably, the models are effective even in the presence of a low temperature noise. References: [1] A. Bassi, K. Lochan, S. Satin, T.P. Singh, and H. Ulbricht, Rev. Mod. Phys. 85, 471 (2013) [2] G.C. Ghirardi, A. Rimini, and T. Weber, Phys. Rev. D 34, 470 (1986) [3] G.C. Ghirardi, P. Pearle, and A. Rimini, Phys. Rev. A 42, 78 (1990) [4] A. Smirne, B. Vacchini and A. Bassi, Phys. Rev. A 90, 062135 (2014) [5] A. Smirne and A. Bassi, arXiv:1408.6446 (2014)
Speaker: Andrea Smirne (University of Ulm) Material: Slides

14:30
Quantum Physics without Quantum Philosophy
45'

09:30  13:00
Testing fundamental principles


09:30  13:00
Quantum complex system

09:30
Quantum effects in complex materials: Determinism, statistics, structure
45'
During the last couple of years, due to tremendous progresses on the experimental side, there has been an intensified debate on the possible role of quantum mechanics in the context of biophysics  i.e. in systems which are rightfully characterized as widely open, disordered, noisy, “complex”. Inspired by some analogies between paradigmes of biological and technological lightenergy conversion, also a possible contribution of quantum science to enhanced, green energy technologies is under discussion. The talk will attempt to summarize the current state of the debate, and to provide a perspective on the challenging problems ahead.
Speaker: Andres Buchleitner (University of Freiburg) Material: Slides 
10:15
Sensitized upconversion with sunlight
45'
It is well known that the efficiency of photovoltaic cells can benefit from upconversion of subbandgap light. Upconversion by triplettripletannihilation is a very promising mechanism for this application. It employs two molecular species, one of which emits higher energy photons via fluorescence upon triplettripletannihilation, whereas the second species sensitizes this process by supplying excitations for the annihilation process. These sensitizers absorb low energy photons with an efficiency that enables successful upconversion already with incoherent sunlight. In my talk, I will give a short introduction to the topic, characterize the transport phenomena in stateoftheart upconversion materials and present ways to further improve the efficiency of the upconversion process.
Speaker: Jochen Zimmermann (University of Freiburg) Material: Slides  11:00 Coffee Break 30'

11:30
Quantum complexity in biological and material systems  Where do we stand?
45'
An overview will be given of our current understanding of quantum complexity and the quantumclassical boundary in biological and material systems. In particular, we will discuss (i) whether "quantumdriven" functionality in these highdimensional, structured systems is a robust feature or rather an accidental occurrence, (ii) to what extent quantum entanglement "scales up" into these systems that are at the border between the microscopic and macroscopic world, (iii) whether specific environments could act so as to protect lowdimensional subsystems from decoherence, and (iv) to what extent effective descriptions of these systems can be found.
Speaker: Irene Burghardt (University of Frankfurt) Material: Slides 
12:15
Quantum dynamics of large systems  challenges and possible solutions
45'
Quantum dynamics is ubiquitous in chemistry; it underlies photochemistry, electron transfer processes, nonradiative transitions, spectroscopy and much more. However, elucidating the quantum dynamics of complex systems remains a central challenge. The problem has two aspects to it. One is the cost of solution of the time dependent Schrödinger equation which typically grows exponentially with the dimensionality of the system. Not less problematic is the fact that quantum dynamics is nonlocal in general and depends on the global potential surface which is rather difficult to generate, for systems with many degrees of freedom. In this talk I will review the main methodologies available for solution of the quantum dynamics and the promise of further progress based on the use of onthefly semiclassical methods.
Speaker: Eli Pollack (Weizmann Institute  Rehovot) Material: Slides

09:30
Quantum effects in complex materials: Determinism, statistics, structure
45'
 13:00  14:30 Lunch

09:30  13:00
Quantum complex system


09:30  13:00
Quantum gravity

09:30
String Theory and Quantum Gravity
45'
Well known problems arise when trying to construct a quantum theory of gravity. After introducing string theory, we will review how string theory addresses these problems (and other problems in theoretical physics), and at which cost.
Speaker: Luis Alday (University of Oxford) Material: Slides 
10:15
The AdS/CFT duality
45'
The AdS/CFT duality brought the holographic principle to center stage in string theory. This correspondence relates theories of gravity on curved spaces to ordinary quantum field theories on the boundaries of those spaces. Due to its nature, it provides a tool for studying strongly interacting field theories, where perturbative methods are not applicable. In this talk I will discuss this duality and present some examples of its realisation.
Speaker: Agnese Bissi (University of Oxford) Material: Slides  11:00 Coffee Break 30'

11:30
Lessons for Quantum Foundations from Quantum Gravity
45'
My title could seem like a joke: what could quantum theory  with its 90 years of success covering a huge range of scales and an enormous variety of phenomena  possibly learn from quantum gravity, a theory that doesn't exist yet? I will argue that one approach to the problem of quantum gravity, in which spacetime is postulated to be fundamentally discrete or atomic, points in a direction that could have implications for our understanding of all quantum systems.
Speaker: Fay Dowker (Imperial College London) Material: Slides 
12:15
Cosmological and Dynamical Aspects of Quantum Gravity with Torsion
45'
In the context of concrete models of torsionful geometries of quantum gravity, in particular the ones inspired from string theory, I discuss the role of torsionful backgrounds in the early Universe in providing scenarios for the observed matter/antimatter asymmetry. In particular, within the context of KalbRamond torsion that arises due to the antisymmetric tensor field in the spectrum of stringinspired models, which in four spacetime dimensions is equivalent to a sort of axion field, I discuss the role of constant (Lorentzviolating) backgrounds of the torsion for Leptogenesis and subsequent Baryogenesis. The effective field theory corresponding to such situations has the form of some terms in the so called Standard Model Extension of Kostelecky and collaborators. I also discuss the role of quantum fluctuations of the torsion, and argue that, under certain circumstances, it may also be held responsible for dynamical generation of chiral Majorana neutrino masses in novel mechanisms beyond seesaw, proceeding through chiral anomalous graphs in the pertinent field theory.
Speaker: Nick Mavromatos (Kings College London) Material: Slides

09:30
String Theory and Quantum Gravity
45'
 13:00  14:30 Lunch

14:30  18:00
Ghirardi Fest  80 years in science

14:30
Nonlocality and Ontology: What Bell and Einstein, Bohm, and Ghirardi showed.
45'
I will briefly discuss three issues of fundamental physical significance for our quantum world, issues on which GianCarlo Ghirardi has worked long and hard and with great success: quantum nonlocality, the measurement problem, and the importance of local beables.
Speaker: Shelly Goldstein (Rutgers University) Material: Slides 
15:15
Correlations beyond entanglement
45'
Separable states may have a kind of correlation which cannot be captured by standard measures of entanglement. These states do not violate Bell inequality and yet they can give computational power to quantum computers which surpass any classical computer. We discuss these states and in particular we focus on a wellknown subclass of them called Werner states. We point out an intriguing property of these states and relate it to the impossibility of a universal NOT operation in quantum mechanics.
Speaker: Vahid Karimipour (Sharif University) Material: Slides  16:00 Coffee Break 30'

16:30
The experimental test of GRW: interferometry and beyond
45'
Recent progress in technological developments allow to explore the quantum properties of very complex systems, bringing the question of whether also macroscopic systems share such features, within experimental reach. It seems feasible to generate for instance quantum superposition states of particles of mass of one million amu (atomic mass unit) [1]. The interest in such experiments is increased by the fact that, on the theory side, many suggest that the quantum superposition principle is not exact, departures from it being the larger, the more macroscopic the system [2]. We will put a special emphasis on possible tests of the GRW model, which provides the most challenging parameter set. We will report on new proposals to experimentally test the superposition principle with noninterferometric methods. Testing the superposition principle intrinsically also means to test suggested extensions of quantum theory, socalled collapse models. Such collapse models predict a heating effect, which results in a random motion of any isolated particle in space. The heating can be monitored using optomechanical systems even in the classical regime, if competing sources of heat can be reduced sufficiently. We will emphasise levitated optomechanical systems and discuss the possibility to test the heating effect by detecting the motion of the particle in space [4] as well as in the frequency domain where heating is manifested as spectral broadening [5]. We will show quantitative calculations for experiments in both regimes and compare to the stateoftheart. We will also report on the status of our experiments on optical levitation and parametric feedback cooling of the 3d motion of dielectric nanoparticles at high vacuum conditions. References [1] Bateman, J., S. Nimmrichter, K. Hornberger, and H. Ulbricht, Nearfield interferometry of a freefalling nanoparticle from a pointlike source, Nat. Com. 5, 4788 (2014). [2] Bassi, A., K. Lochan, S. Satin, T.P. Singh, and H. Ulbricht, Models of Wavefunction Collapse, Underlying Theories, and Experimental Tests, Rev. Mod. Phys. 85, 471  527 (2013). [3] Bahrami, M., A. Bassi, and H. Ulbricht, Testing the quantum superposition principle in the frequency domain, Phys. Rev. A 89, 032127 (2014). [4] Bera, S., B. Motwani, T.P. Singh, and H. Ulbricht, A proposal for the experimental detection of CSL induced random walk, Sci. Rep. 5, 7664 (2015). [5] Bahrami, M., M. Paternostro, A. Bassi, and H. Ulbricht, Noninterferometric Test of Collapse Models in Optomechanical Systems, Phys. Rev. Lett. 112, 210404 (2014).
Speaker: Hendrik Ulbricht (University of Southampton) Material: Slides 
17:15
Talk 28
45'

14:30
Nonlocality and Ontology: What Bell and Einstein, Bohm, and Ghirardi showed.
45'

09:30  13:00
Quantum gravity


09:30  13:00
Gravity and Cosmology

09:30
Fundamental issues in gravity theory and its relation to Quantum Mechanics
45'
I will discuss several conceptually interesting open problems in General Relativity, including those relating to Quantum Mechanics.
Speaker: Domenico Giulini (University of Hannover) Material: Slides 
10:15
Prospects of experimental tests of a fundamentally semiclassical gravitation theory
45'
I discuss the hypothetical possibility of a theory in which only matter is quantised, but gravity is described by the classical theory of General Relativity, even at the fundamental level. From the most naive approach for such a theory, one obtains the SchrödingerNewton equation as a nonrelativistic limit. I present possibilities of experimental tests of such an alternative to Quantum Gravity.
Speaker: Andre Grossardt (University of Trieste) Material: Slides  11:00 Coffee Break 30'

11:30
Must spacetime be singular?
45'
According to Einstein's theory of general relativity spacetime singularities such as a big bang may occur. Moreover, the PenroseHawking theorems showed that such singularities are actually generic. It has been believed that a quantum theory for gravity might avoid such singularities. The answer will of course depend on which approach to quantum gravity one considers. It will also depend on which version of quantum theory one adopts. In this talk, we will consider the question in the context of the Bohmian version of quantum mechanics, for the special case of a homogeneous and isotropic universe. According to the Bohmian approach there is an actual spacetime metric. So one immediate virtue of this approach is that the question in our title is wellposed, having the same meaning as in Einstein's theory. We show that there is a nonzero probability for the spacetime to be nonsingular in the case of the WheelerDeWitt approach to quantum gravity, while it is one in the case of loop quantum gravity. This is in contrast to the consistent histories approach to quantum theory which predicts a singularity for the WheelerDeWitt approach with probability one.
Speaker: Ward Struyve (LMU Munich) Material: Slides 
12:15
Gravity related spontaneous decoherence: from WheelerBekensteinHawking to optomechanics
45'
The inception of a universal gravityrelated irreversibility took place originally in quantum cosmology but it turned out soon that a universal nonunitary dynamics is problematic itself. Independent investigations of the quantum measurement postulate clarified that a nonunitary dynamics is of interest already in the nonrelativistic context. An intricate relationship between Newton gravity and quantized bulk matter might result in universal nonrelativistic violation of unitarity  also called spontaneous decoherence. The corresponding gravityrelated spontaneous decoherence model is now on the verge of detectability in optomechanical experiments. It is also a toymodel of cosmic quantumgravitational nonunitarity, illuminating that the bottleneck of quantumgravity is the quantum measurement postulate instead of quantum cosmology.
Speaker: Lajos Diosi (Wigner Research Center for Physics) Material: Slides

09:30
Fundamental issues in gravity theory and its relation to Quantum Mechanics
45'
 13:00  14:30 Lunch

14:30  16:00
MC meeting of the Cost Action

09:30  13:00
Gravity and Cosmology