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"Quantum Mechanics Tests in Particle, Atomic, Nuclear and Complex Systems: 50 years after Bell's renowned theorem"

COST Action MP1006 , organized by Beatrix C. Hiesmayr, Catatlina Curceanu and Andreas Buchleitner

When? 24. - 28. Februar 2014
Where? ECT* Trento (Italy), http://www.ectstar.eu/
Why?TThe aim of this workshop is to discuss entanglement, decoherence and quantum interference in complex systems within Particle, Nuclear, Atomic, Photonic and Condensed Matter Physics and including Biological Systems. It will bring together theoreticians and experimenters of these distinct fields with the attempt to build up a strategy for systematic tests of quantum theory and to exchange fruitful methods. The workshop is devoted to John Bell who initiated this line of research and we are happy to announce that we will have speakers who will report on their personal interactions with John Bell. The workshop is supported by COST action MP1006 and ECT*.

How to apply? Send an email to Beatrix Hiesmayr

Beatrix Hiesmayr

Speakers (*not yet confirmed):

Mohammad Bahrami ("Testing the quantum superposition principle in the frequency domain", abstract)
Angelo Bassi ("Why and how collapse models affect the radiative properties of matter.", abstract)
Rita Bernabei ("Recent DAMA/LIBRA results and the perspectives", abstract)
Reinhold Bertlmann ("TBA", abstract)
Tobias Brandes ("Maxwell's demon in a quantum system", abstract)
Irene Burghardt ("Does coherent quantum dynamics guide the charge separation in organic solar cells?", abstract)
Steve Campbell ("General Quantum Correlations in Critical Spin Systems", abstract)
Elisabetta Collini ("Spectroscopic signatures of vibronic coherence in artificial dimers: evidence for quantum energy transfer?", abstract)
Catalina Curreanu ("From the Vonnegut’s chrono-synclastic infundibulum to the collapse of the wave function", abstract)
Alexis Diaz-Torres ("Probing the dynamics of open quantum systems with elastic scattering of halo nuclei", abstract)
Antonio Di Domenico ("Testing fundamental physical principles with entangled neutral K mesons", abstract)
Sandro Donadi ("Flavour oscillations (mesons, neutrinos) in collapse models", abstract)
Thomas Durt ("Crucial tests of macrorealist and semi-classical gravity models with freely falling mesoscopic microspheres", abstract)
Stefan Filipp ("Testing Quantum Mechanics with Superconducting Artificial Atoms", abstract)
Nicolai Friis ("On the robustness of entanglement in analogue gravity systems", abstract)
Philipp Haslinger ("Matter-wave interferometry with gratings made of light", abstract)
Marcus Huber ("Revealing entanglement in high-dimensional systems", abstract)
Fabrizio Illuminati
Gerd Krizek ("Einsteins 1935 papers", abstract)
Andrzej Kupsc ("Searches for a dark photon", abstract)
Marco Genovese ("An experimental approach to the nature of time in quantum mechanics", abstract)
Gian Carlo Ghirardi ("Recollections of J. Bell ", abstract)
Marco Giampaolo ("Analyzing Genuine Multipartite Entanglement in Condensed Matter Systems", abstract)
Wolfgang Löffler ("Revealing bound entanglement of twisted photons and 4-photon transverse-mode entanglement", abstract)
Miguel Angel Martin-Delgado ("TBA", abstract)
Johannes Marton ("VIP2 - New precision tests of the Pauli Exclusion Principle for Electrons", abstract)
Eduardo Milotti ("Using photon-photon scattering to investigate the nature of quantum vacuum", abstract)
Pawel Moskal ("Positronium:  a laboratory for tesingt quantum mechanics and a tool for medical imaging", abstract)
Igor Pikovski ("Universal decoherence due to gravitational time dilation", abstract)
Elisabet Romero ("TBA", abstract)
Fabio Sciarrino ("Testing fundamental principles of quantum mechanics", abstract)
Malte C. Tichy ("Entanglement, bosons and fermions", abstract)
Markus Tiersch ("Towards validating entanglement in radical pair systems", abstract)
Hendrik Ulbricht ("Testing Macroscopic Quantum Superposition", abstract)
Joan Vaccaro ("Entanglement on a cosmological scale", abstract)
Martin Weitz ("Particles of light: Thermodynamics and Bose-Einstein condensation of light
in a photon box
", abstract)




Author: Wolfgang Löffler
Title: Revealing bound entanglement of twisted photons and 4-photon transverse-mode entanglement
Abstract: Firstly, we report on an experiment [1] that witnesses for the first time the generation of bound entanglement of two photon qutrits, whose existence has been predicted by the Horodecki family in 1998. Detection of these heavily mixed entangled states, from which no pure entanglement can be distilled, is possible using a key concept of Nature: maximum complementarity. Our protocol based on mutually unbiased bases enables ample detection of entanglement in arbitrary high-dimensional systems and number of systems [2], including the most challenging case, the detection of bound entanglement. Secondly, we show first experimental evidence of quantum entanglement of 4 photons in their spatial degrees of freedom, such as orbital angular momentum modes. The photons are produced by high-gain parametric downconversion and are analyzed with spatial light modulators.
[1] B.C. Hiesmayr and W. Löffler, “Complementarity reveals bound entanglement of two twisted photons”, New J. Phys. 15, 083036 (2013).
[2] B.C. Hiesmayr and W. Löffler, “Mutually unbiased bases and bound entanglement”, to be published in Physica Scripta (2014); arXiv:1309.2271.

Author: Joan Vaccaro
Title: Entanglement on a cosmological scale
Abstract: Although unified in special relativity, quantum physics shows that space and time have subtly different symmetry properties.  In particular, the generator of translations in space (the momentum operator) is symmetric with respect to parity inversion, whereas due to the CP and T violation manifested in the weak interaction, the generator of translations in time (the Hamiltonian) is not symmetric with respect to time reversal.  This talk explores the implications of this difference for a toy model of the universe.  I will start with a model universe which is symmetric with respect to both parity inversion and time reversal, and show that it can be described by a single Gaussian state spread over space and time, much like the Block universe.  Next I will show that by introducing a sufficient degree of the violation of time reversal invariance, the situation changes dramatically and no single state is sufficient to describe the universe.  Instead, the universe is best described by a sequence of states that are entangled in time on a cosmological scale.

Author: Mohammad Bahrami
Title: Testing the quantum superposition principle in the frequency domain
Abstract: We propose a novel way of testing the quantum superposition principle, competitive with respect to the traditional schemes, based on measuring the spectral properties of atoms and molecules. We show that spectral lineshapes are modified, if the superposition principle is violated. We quantify the magnitude of the violation, for relevant collapse models. We show how this effect can be distinguished from that of standard environmental noises (decoherence). We argue that accurate enough spectroscopic experiments are within reach, with current technology.

Author: Gerd Krizek
Title: Einsteins Paper
Abstract: In May of 1935 Albert Einstein published his famous EPR paper \Can Quantum-Mechanical Des-
cription of Physical Reality Be Considered Complete? [3]. In July Einstein published together with
his assistant Nathan Rosen, who was also co-author of the EPR paper, a paper which became famous
as well:\The Particle Problem in the General Theory of Relativity [4]. In this paper Einstein and
Rosen found the famous Einstein-Rosen-Bridge solutions for the eld equations of general relativity.
It is remarkable that both papers appeared in a short period of time and both ask for completen-
ess as the foundation of a theory. Recent claims by Maldacena, Susskind [1] and Jensen,Karch [2] to
understand entanglement in terms of Einstein-Rosen bridges raise the question what Einstein had
in mind during his work on his 1935 papers. I will discuss the relation between Einsteins famous
papers with focus on this question and what we can learn about Einsteins understanding of reality.
[1] J. Maldacena, L.Susskind, arxiv:1306.0533v2
[2] K. Jensen, A. Karch(2013),"Holographic Dual of an Einstein-Podolsky-Rosen Pair has a wormhole"Physical
review letters PRL 111.211602
[3] A. Einstein, B. Podolsky and N. Rosen(1935), "Can quantum mechanical description of physical reality be
considered complete?,"Phys. Rev. 47, 777
[4] A. Einstein and N. Rosen(1935), "The Particle Problem in the General Theory of Relativity"Phys. Rev.
48, 73

Author: Marco S. Giampaolo
Title: Analyzing Genuine Multipartite Entanglement in Condensed Matter Systems
Abstract: Only since the begining of this century it has been shown that entanglement is present in typical condensed matter systems, however, the role of entanglement is unclear. For example, it is conjectured that entanglement provides the most fundamental characterization of quantum phase transitions of matter. In this talk we investigate the presence of bipartite and genuine multipartite entanglement in the famous XY model [1] which is a very good approximation to real condensed matter systems. Surprisingly, genuine multipartite entanglement is found for nearly all isotropies and values of an external magnetic field. Moreover, the phase transition and scaling properties are fully characterized by the multipartite quantity that we use to detect genuine multipartite entanglement [2]. Consequently, a useful toolbox is provided for which different types of entanglement such as bipartite and multipartite entanglement and even different types of genuine multipartite entanglement can be analyzed. With this toolbox at hand it is the hope that the role of entanglement and its different types of entanglement can be revealed.
[1] S. M. Giampaolo and B.C. Hiesmayr, Phys. Rev. A 88, 052305 (2013).
[2] M. Huber, F. Mintert, A. Gabriel, B.C. Hiesmayr, Phys. Rev. Lett. 104, 210501 (2010); A. Gabriel, B.C. Hiesmayr and M. Huber, Quantum Information and Computation 10, 829 (2010).

Author: Steve Campbell
Title: General Quantum Correlations in Critical Spin Systems
Abstract: Quantum correlations, and in particular entanglement, appear play a crucial role in fundamental phenomena such as quantum phase transitions. The use of quantifiers of these correlations to spotlight and understand criticality in various models has been extremely fruitful. We will show that moving beyond entanglement, and studying general quantum correlations, i.e. quantum discord and related measures, can offer an extremely versatile tool when one wishes to study criticality in adverse situations. In particular, we will show through the use of bipartite and global quantum discord the critical nature of various spin systems can be neatly identified even for finite size systems not in their ground state.

Author: Johannes Marton for the VIP collaboration
Title: VIP2 - New precision tests of the Pauli Exclusion Principle for Electrons
Abstract: One of the fundamental rules of quantum physics is represented by the Pauli Exclusion Principle (PEP). We know that this PEP is extremely well fulfilled due to many observations. In the past many experiments were performed to search for tiny violations of PEP. The experiment VIP at the Gran Sasso underground laboratory (LNGS) is searching for possible small violations of the PEP for electrons leading to forbidden x-ray transitions in copper atoms. The experimental method, results obtained so far and new developments of a succeeding improved experiment VIP2 at Gran Sasso to further increase the sensitivity by 2 orders of magnitude will be presented. Partly supported by FWF project P25529.

Author: Stefan Filipp
Title: Testing Quantum Mechanics with Superconducting Artificial Atoms
Abstract: Superconducting circuits acting as artificial atoms are ideally suited to probe fundamental aspects of quantum mechanics, mainly because of their remarkable controllability and their good coherence properties. In particular, their strong coherent coupling to photons contained in on-chip microwave cavities allows for studying interactions and correlations between multiple particles. Via photon-mediated interactions we have generated entangled quantum states which violate Bell inequalities. Moreover, we have demonstrated the deterministic teleportation of a quantum state in such a macroscopic quantum system. Based on fast feed-forward, the teleportation scheme has been realized with high success probability at fast repetition rates. Finally, we have utilized this system as a digital quantum simulator of interacting spin particles and implemented a quantum simulation of Heisenberg spin-spin interactions within a two-particle setting.

Author: Sandro Donadi
Title:Flavour oscillations (mesons, neutrinos) in collapse models
Abstract:Collapse models are phenomenological models where the evolution of the state vectors is driven by a non-linear and stochastic equation. After a brief introduction to these models, we analyze how the formula describing flavour oscillations is modified when the collapse dynamics is considered in place of the standard quantum linear dynamics. We focus in particular in the case of neutrinos and neutral mesons.

Author: Rita Bernabei
Title: Recent DAMA/LIBRA results and the perspectives
Abstract: Results recently released by the DAMA/LIBRA experiment (about 250 kg full sensitive mass made of highly radiopure NaI(Tl)) on the presence of Dark Matter particles in the galactic halo will be discussed. The data satisfy all the many requirements of the exploited Dark Matter annual modulation signature at high confidence level. Presently DAMA/LIBRA is in data taking in a new configuration (DAMA/LIBRA-phase2) with lower software energy threshold. Comparisons, implications and realistic experimental perspectives of the field will be addressed.

Author: Hendrik Ulbricht
Title: Testing Macroscopic Quantum Superposition
Abstract: New 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. The interest in this question 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 [1]. Testing the superposition principle intrinsically also means to test suggested extensions of quantum theory, so-called collapse models. We will report on three new proposals to experimentally test the superposition principle with nanoparticle interferometry [2], optomechanical devices [3] and by high-resolution spectroscopy [4].

[1] Bassi, A., K. Lochan, S. Satin, T.P. Singh, and H. Ulbricht, Models of Wave-function Collapse, Underlying Theories, and Experimental Tests, Rev. Mod. Phys. 85, 471 - 527 (2013). [2] Bateman, J., S. Nimmrichter, K. Hornberger, and H. Ulbricht, Near-field interferometry of a free-falling nanoparticle from a point-like source, arXiv:1312.0500 (2013). [3] Xuereb, A., H. Ulbricht, and M. Paternostro, Optomechanical interface for matter-wave interferometry, Nature Scientific Reports 3, 3378 (2013). [4] Bahrami, M., A. Bassi, and H. Ulbricht, Testing the quantum superposition principle in the frequency domain, arXiv:1309.5889 (2013).

Authors: Philipp Haslinger, Nadine Dörre, Jonas Rodewald, Philipp Geyer, Stefan Nimmrichter, Klaus Hornberger, and Markus Arndt
Title :Matter-wave interferometry with gratings made of light
Abstract: Matter-wave interferometry with complex and massive particles has shown great progress in the last decades [1–5]. The recent demonstration of the OTIMA (Optical Time-domain Ionizing Matter-wave) interferometer [6] has proven the capability of optical VUV gratings as a tool to coherently manipulate particles. In this Talbot-Lau interferometer arrangement, all gratings are formed by 5-8 ns long laser pulses at a wavelength of 157 nm. This wavelength is short enough to achieve single photon ionization of a broad range of atoms, molecules and nanoparticles. In combination with an external electric field, these laser pulses act as absorptive gratings in the time-domain. These pulsed gratings are applied three times with a well-define pulse delay on the free falling molecules in order to prepare a sufficiently wide spatial coherence (1st grating), to diffract them (2nd grating) and to resolve/detect the appearing interference pattern (3rd grating). Quantum interference in the OTIMA setup is not only visible in the spatial interference pattern but also in the mass selective transmission, which is a feature of the time-domain [7]. This has been proven for Anthracene clusters up to a mass of 2300 amu. This interferometer has a capability to interfere particles up to 106 amu. In this mass range, the interferometer has been predicted to test spontaneous localization theories [8] and even certain parameter ranges of dark matter models [9].

[1] M. Arndt, O. Nairz, J. Vos-Andreae, C. Keller, G. van der Zouw, and A. Zeilinger, Nature 401, 680 (1999). [2] S. Gerlich, L. Hackermüller, K. Hornberger, A. Stibor, H. Ulbricht, M. Gring, F. Goldfarb, T. Savas, M. Müri, M. Mayor, and M. Arndt, Nat. Phys. 3, 711 (2007). [3] T. Juffmann, A. Milic, M. Müllneritsch, P. Asenbaum, A. Tsukernik, J. Tüxen, M. Mayor, O. Cheshnovsky, and M. Arndt, Nat. Nanotechnol. 7, 297 (2012). [4] S. Eibenberger, S. Gerlich, M. Arndt, M. Mayor, and J. Tüxen, Phys. Chem. Chem. Phys. 15, 14696 (2013). [5] K. Hornberger, S. Gerlich, P. Haslinger, S. Nimmrichter, and M. Arndt, Rev. Mod. Phys. 84, 157 (2012). [6] P. Haslinger, N. Dörre, P. Geyer, J. Rodewald, S. Nimmrichter, and M. Arndt, Nat. Phys. 9, 144 (2013). [7] S. Nimmrichter, P. Haslinger, K. Hornberger, and M. Arndt, New J. Phys. 13, 075002 (2011). [8] S. Nimmrichter, K. Hornberger, P. Haslinger, and M. Arndt, Phys. Rev. A 83, 043621 (2011). [9] C. Riedel, Phys. Rev. D 88, 116005 (2013).

Author: Antonio Di Domenico
Title: Testing fundamental physical principles with entangled neutral K mesons
Abstract: The neutral kaon doublet is one of the most intriguing systems in nature. Entangled pairs of neutral K mesons produced in phi decays offers a unique possibility to perform very precise tests of fundamental discrete symmetries in nature, as well as of basic principles of quantum mechanics. The most recent results will be reviewed and perspectives in the field will be discussed.

Author: Igor Pikovski
Title: Universal decoherence due to gravitational time dilation
Abstract: Phenomena inherent to quantum theory on curved space-time, such as Hawking radiation, are typically assumed to be only relevant at extreme physical conditions: at high energies and in strong gravitational fields. Here we consider low-energy quantum mechanics in the presence of weak gravitational time dilation and show that the latter leads to universal decoherence of quantum superpositions. Time dilation induces a universal coupling between internal degrees of freedom and the centre-of-mass of a composite particle and we show that the resulting entanglement causes the particle's position to decohere. We derive the decoherence time scale and show that the weak time dilation on Earth is already sufficient to decohere micro-scale objects. No coupling to an external environment is necessary, thus even completely isolated composite systems will decohere in the presence of time dilation. In contrast to gravitational collapse models, no modification of quantum theory is assumed. General relativity therefore can account for the emergence of classicality and the effect can in principle be tested in future matter wave experiments with large molecules or with trapped microspheres.

Author: Edoardo Milotti
Title: Using photon-photon scattering to investigate the nature of quantum vacuum
Abstract: Photon-photon scattering is an elusive and yet extremely important process, which offers a unique glimpse into the vacuum of quantum electrodynamics. Here I discuss the experimental opportunities of a direct observation of this process, and their relevance to our understanding of quantum vacuum.

Author: Pawel Moskal
Title :Positronium:  a laboratory for tesingt quantum mechanics and a tool for medical imaging
Abstract: tba

Author: Irene Burghardt
Title: Revealing bound entanglement of twisted photons and 4-photon transverse-mode entanglement
Abstract: As highlighted by recent experiments, elementary processes in organic photovoltaics can be guided by quantum coherence, despite the presence of electron-phonon coupling and static and dynamic disorder. We present quantum dynamical studies of these processes using the Multi-Configuration Time-Dependent Hartree (MCTDH) method [1], focusing on exciton dissociation in typical donor-acceptor complexes [2,3] representing models of polymer:fullerene heterojunctions. Here, the primary exciton break-up is found to occur within 50-100 femtoseconds and exhibits a pronounced oscillatory decay profile, reflecting vibronic coherence [2]. Furthermore, rapid free carrier generation from the interfacial charge transfer (CT) state is feasible, due to an effective lowering of the Coulomb barrier as a result of charge delocalization, along with the vibronically hot nature of the primary CT state [3]. Against this background, the role of coherent quantum effects in complex (bio)material systems will be discussed.
[1] G. A. Worth, H.-D. Meyer, H. Koeppel, L. S. Cederbaum, I. Burghardt, Int. Rev. Phys. Chem., 27, 569 (2008);
[2] H. Tamura, R. Martinazzo, M. Ruckenbauer, I. Burghardt, J. Chem. Phys., 137, 22A540 (2012);
[3] H. Tamura, I. Burghardt, J. Am. Chem. Soc. (Comm.), 135, 16364 (2013).


Author: Malte Tichy
Title: Entanglement, bosons and fermions
Abstract: Despite the analogies between the quantum-mechanical treatment of identical particles and quantum entanglement, the acceptance and perception of the latter turned out to be much more laborious than the former. Today, entanglement and the many-particle coherence of bosonic and fermionic states can be explored experimentally. Beyond the two-particle paradigm, the interplay of coherence and complexity governs the relationship between entanglement and identical particles: On the one hand, the intrinsic many-body coherence of bosons and fermions can generate complex multipartite quantum correlations. On the other hand, complexity is also a source of coherence: Composite systems of two bound particles need to be sufficiently entangled to exhibit ideal bosonic or fermionic behavior, making entanglement observable in interference experiments.

Author: Elisabetta Collini
Title: Spectroscopic signatures of vibronic coherence in artificial dimers: evidence for quantum energy transfer?
Abstract: One of the most surprising and significant advances in the study of the photosynthetic light-harvesting process is the discovery that the electronic energy transfer might involve long-lived electronic coherences, also at physiologically relevant conditions. This means that the transfer of energy among different chromophores does not follow the expected classical incoherent hopping mechanism, but that quantum-mechanical laws can steer the migration of energy. The implications of such quantum transport regime, although currently under debate, might have a tremendous impact in our way to think about natural and artificial light-harvesting. Central to these discoveries has been the development of new ultrafast spectroscopic techniques, in particular two-dimensional electronic spectroscopy, which is now the primary tool to obtain clear and definitive experimental proof of such effects. In this seminar I will present the early time dynamics of energy migration in a homo-dimer of a quadrupolar chromophore characterized by 2D electronic spectroscopy, treated as model system of more sophisticated natural and artificial light-harvesting complexes. In agreement with recent theoretical predictions, the obtained results suggest the presence of strong interactions between electronic and vibrational degrees of freedom leading to a rich oscillatory pattern of vibronic coherences, not present in the single monomeric units. The possible connection between such experimentally detected coherences and quantum regime of energy transport will be discussed.

Author: Catalina Curceanu
Title: From the Vonnegut’s chrono-synclastic infundibulum to the collapse of the wave function
Abstract: The “measurement problem” continues to remain – at least for part of the community – a problem in need of an explanation. While some claim to have solved the problem (many supporting the idea that there is no problem at all) others are digging into the theory, eventually modifying the well-known framework of the quantum mechanics, in particular the Schrodinger equation. This modification (dynamical reduction model) has important experimental consequences which can be looked for. We discuss various ideas to find (some) experimental signatures for the collapse of the wave function within the dynamical reduction models, starting with the measurement of the spontaneously emitted X rays predicted in the framework the new theory. The dynamical reduction models were put forward alternatively to the "standard" quantum mechanics' Schrodinger equation, followed by a "alla von Neumann" collapse of the wave-function, implementing a (nonrelativistic) dynamical reduction/collapse models, by modifying with a non-linear and stochastic terms the Schrodinger equation. Baring on the importance of this conceptually new model(s), it is of utmost importance to study its experimental consequences, where the predictions are diverging from the standard equations, and to perform dedicated experiments to check it. One can then extend the findings not only, obviously, to the modern physics, but to items such as the chrono-synclastic infundibulum Vonnegut put forward in his novel, Titan Sirens, where Rumfoord and Kazak’s wave function(s) do collapse in a very interesting manner.

Author: Nico Friis
Title: On the robustness of entanglement in analogue gravity systems
Abstract: We investigate the possibility to generate quantum-correlated quasi-particles utilizing analogue gravity (AG) systems. The quantumness of these correlations is a key aspect of AG effects and their presence allows for a clear separation between classical and quantum AG effects. However, experiments in analogue systems, such as Bose-Einstein condensates are always conducted at non-ideal conditions. In particular, one is dealing with dispersive media at nonzero temperatures. We analyze the influence of the initial temperature on the entanglement generation in AG phenomena. [1] D. E. Bruschi, N. Friis, I. Fuentes, and S. Weinfurtner, New J. Phys. 15, 113016 (2013).

Author: Angelo Bassi
Title: Why and how collapse models affect the radiative properties of matter.
Abstract: According to collapse models (GRW, CSL, ...), particles jiggle in space under the influence of the "collapse noise". Therefore, if they are charged, they radiate. The problem of spontaneous photon emission in collapse models is interesting both from the theoretical point of view, as well as from the experimental one. On the theory side, it is a challenging combination of quantum field theory, electromagnetism and stochastic processes. From the experimental side, it provides the strongest upper bound on the collapse parameters, thus far. We will present the state of the art, the most recent results, and future possible experiments.

Author: Alexis Diaz-Torres
Title: Probing the dynamics of open quantum systems with elastic scattering of halo nuclei
Abstract:The dynamics of an open quantum system may also be revealed in the low-energy elastic scattering of halo nuclei [1]- a conventional core nucleus surrounded by a loosely bound halo of orbiting neutron(s) or proton(s), as the elastic channel (sub-system) strongly interacts with the continuum of breakup channels (environment). Recent measurements of (quasi)elastic-scattering angular distribution have shown a strong suppression of the Coulomb-nuclear interference peak [2]. Examining the components of the elastic differential cross sections for 11Be + 64Zn and 6He + 208Pb at energies near the Coulomb barrier, this appears to be caused by a dramatic phase-change (destructive) of the attenuated Coulomb-nuclear interference term due to continuum couplings.
[1] A.S. Jensen et al., Rev. Mod. Phys. 76 (2004) 711.
[2] A. Di Pietro et al., Phys. Rev. Lett. 105 (2010) 022701.