INVITED TALKS

A. Eichorn Towards an understanding of the quantum-gravity matter interplay

Abstract: I will argue that in order to use quantum systems to test potential phenomenological consequences of quantum spacetime, an understanding of the interplay of quantum gravity and matter from first principles is necessary. I will introduce the asymptotic safety paradigm as a strong contender for a viable microscopic model of quantum gravity and matter and will highlight recent progress on how to bridge the gap between the microscopic scales of the model and macroscopic scales, at which observations are possible.

S. Liberati Quantum gravity phenomenology: an overview

Abstract: In this talk I will provide a brief overview of extant line of investigations and perspectives towards testing quantum gravity scenarios and discuss some of the lessons we have learned so far.

G. Amelino-Camelia The different notions of observer used in quantum theory and in relativity

Abstract: The description of observers (and "agents") in quantum gravity will likely require a sort of synthesis of the corresponding descriptions presently in use in quantum theory and in relativity; however, in modern analysis of the role of observers in physics sharply different pictures arise between the quantum-theory side and the relativity side. Are these differences structural or cultural? I sketch out a research program which could attempt to bring the gap in the decription of observers ont he two sides, hopefully preparing us for facing the relevant task in quantum gravity.

D. Giulini (tbc)

W. Unruh TBA

R. Sorkin Why should (and why can) the path integral serve as the basis  for quantum theory and quantum gravity?

Abstract: For many people, a quantum theory must have momentary states, observable operators, and a Hamiltonian, but if one takes as one’s point of departure the path integral rather than the Schroedinger equation, one arrives at a formulation resting on histories rather than wave functions.Understood in this way, the path integral is not a merely technical tool which exhausts itself in computing the propagator, but something that can stand alone as a complete foundation for a quantum theory.  And I'll claim that this provides the form of quantum mechanics that gravity needs!To go beyond the conception of PI as a propagator, however, one needs to work with the "quantum measure", defined via a double path integral (DPI).In relation to gravity, the definition of the DPI raises some important and neglected questions.  This was part I of the talk. Part II, in case I get to it, will show the gravitational PI “in action" in relation to topological geons, topology change in 2D, and birth of the cosmos by tunneling.

D. Greenberger The case for Mass and Proper Time as Dynamical Variables.

Abstract: TBA

R. Wald Quantum Superposition of Massive Objects and the Quantization of Gravity

Abstract: We analyse a gedankenexperiment previously considered by Mari et al. that involves quantum superpositions of charged and/or massive bodies (``particles'') under the control of the observers, Alice and Bob. In the electromagnetic case, we show that the quantization of electromagnetic radiation (which causes decoherence of Alice's particle) and vacuum fluctuations of the electromagnetic field (which limits Bob's ability to localize his particle to better than a charge-radius) both are essential for avoiding apparent paradoxes with causality and complementarity. We then analyze the gravitational version of this gedankenexperiment. We correct an error in the analysis of Mari et al. and of Baym and Ozawa, who did not properly account for the conservation of center of mass of an isolated system. We show that the analysis of the gravitational

case is in complete parallel with the electromagnetic case provided that gravitational radiation is quantized and that vacuum fluctuations limit the localization of a particle to no better than a Planck length. This provides support for the view that (linearized) gravity should have a quantum field description.

S. Bose Probing the Quantum Coherent Behaviour of Gravity

Abstract: A lack of empirical evidence has lead to a debate on whether gravity is a quantum entity.  Motivated by this, I will present a feasible idea for such a test based on the principle that two objects cannot be entangled without a quantum mediator. I will show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. A prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, is also provided and can be measured through simple spin correlations.

M. Blencowe Gravitational Decoherence

Abstract: Working within standard linearized gravity + massive scalar field, we consider an initial Gaussian, single particle wavepacket state that 'falls' under the combined influence of a weak background gravitational field and a thermal gravity wave environment. We evaluate the wavepacket dispersion rate as probed by the scalar field's two-point  correlation function and interpret in terms of gravitational dephasing/decoherence. The motivations behind the latter approach are to avoid initial 'bursts' of decoherence that are an artifact of usually assuming initial system superposition-thermal environment product states and also to quantify decoherence through observable quantities.

R. Schützhold Interaction of a Bose-Einstein condensate with a gravitational wave

Abstract: Partly motivated by recent proposals for the table-top detection of gravitational waves, we study their interaction with Bose-Einstein condensates and compare our results to the proposals in the literature.

M. Kasevich Tests of quantum mechanics and gravitation with atom interferometry

Abstract: Recent de Broglie wave interference experiments with atoms have achieved wavepacket separations as large as 54 cm over time intervals of 2 sec [1, 2]. These experiments, and their impact on gravitational and quantum physics, will be discussed. [1] Kovachy, T. et al. Quantum superposition at the half-metre scale. Nature 528, 530–533 (2015). [2] Asenbaum, P. et al. Phase Shift in an Atom Interferometer due to Spacetime Curvature across its Wave Function. Physical Review Letters 118, (2017).

A. Abele TBA

S. Weinfurtner Analogue gravity experiments in Nottingham

Abstract: TBA

R. Ursin Quantum optics experiment in a relativistic environment

Abstract: Gravity, continues to hold out against physicists' efforts of including it into the framework of quantum theory. Experimental techniques in quantum optics have only recently reached the precision and maturity required for the investigation of quantum systems under the influence of gravitational fields. I will report on experiments in which a genuine quantum state of an entangled photon pair was exposed to micro- and hyper-acceleration [1]. I will also report on the status of the Space-QUEST mission at the ESA level, where the decoherence of an entangled photon state shall be tested on an optical free space link between ground and a satellite receiver platform [2]. I will also present some possible experiments which are feasible to do to help to give some guidance to yet uncertain theories.

M. Zych Relativity of quantum superpositions

Abstract: In modern physical theories only relative quantities are considered to have physical significance.   For example, position assigned to a system depends on the choice of a coordinates — only the relative distances between different systems have physical relevance.  On the other hand, in quantum theory the scenario where one system, A,  is localised around certain position while another system, B, is in a spatial superposition is considered to be physically different from the scenario where A is in a superposition, while B is localised. Different physical effects are anticipated in the two scenarios especially when the two systems have widely different masses.  Here we show that  as long as the superposed amplitudes are related by a symmetry transformation, the above scenarios are physically equivalent: probabilities for any measurement are the same whether we assign the superposition state to system A or to system B. More generally, linearity of quantum theory guarantees that if a theory is invariant under certain symmetry transformations it is also invariant under arbitrary “superpositions” of these transformations. The notion of a superposition can therefore be treated as relative to the choice of coordinates —   once we consider that relations between coordinate systems do not need to be classical.

F. Costa Algebraic Quantum Fields with Quantum Causal Structure

Abstract: Quantum field theory is the most successful framework to describe fundamental physics, combining the principles of quantum theory and relativity. Yet, most formalisations of the theory treat space and time differently, most prominently postulating that space-like separated field operators must commute, while time-like fields do not. Such a dichotomy poses conceptual challenges towards extending the framework to physical scenarios where the causal structure is not defined a priori, and can be dynamical and quantum. I will present an algebraic approach to quantum field theory that does not require a background causal structure and thus makes no a priori distinction between space and time. Imposing a particular causal structure is formally equivalent to assigning a state, leading to a natural notion of fields with quantum causal structure.

T. Osborne Locality and tensor network models for spacetime

Abstract: Tensor network models for spacetime have enjoyed considerable recent interest and, in particular, have been helpful in understanding the AdS/CFT correspondence. However, what exactly is a tensor network model for a given spacetime? Certainly we know one when we see one, e.g., the multiscale entanglement

renormalisation ansatz is clearly a good model for a (time slice of) AdS. Here I'll discuss this problem and its connection with the operational task of defining locality; I'll argue that a tensor network model is a (projective) unitary representation of the symmetry group of a spacetime via tensor-network unitary operators.

M. Martin-Benito Challenging Area Laws: Are black holes really the ultimate entrops?

Abstract: We revisit the common lore that black holes are the objects that maximize entropy at a given energy. This belief is supported by the relations between energy and entropy in regular matter. We challenge this common belief in two different ways:

-First we see how assuming that black holes are the “ultimate entrops” would impose a bound in the number of particle species and internal degrees of freedom of fermion and boson gasses that we have no guarantee to fulfill from first principles.

-More importantly, we also show that there are certain quantum field states on which we can act locally and increase their entropy while reducing their energy. Effectively this would allow us to increase the entanglement entropy of the localized field with the rest of the universe while reducing the Bekenstein-Hawking entropy of the black hole that these field excitations would form under gravitational collapse.

In summary, we will provide evidence that the Bekenstein-Hawking entropy may not be fundamentally linked in general with the entanglement entropy of the microscopic degrees of freedom of the matter that produces a black hole.

L. Hardy TBA

A. Kent Quantum Summoning: Theory and Applications

Abstract: Quantum summoning has emerged as a key primitive task in relativistic quantum information theory.    From a foundational perspective, the (im)possibility of quantum summoning tasks distinguishes relativistic quantum theory from other theories, and is a good candidate for an axiomatic reformulation of relativistic quantum theory based on information-theoretic principles.       Several significant

relativistic quantum cryptographic tasks have also been inspired by summoning and proved secure via summoning (im)possibility results.      I review recent developments extending the range of provably (im)possible summoning tasks and applications to cryptography.

T. Ralph RQI and Quantum Interpretations

Abstract: We take a new look at interpretations such as Bohmian mechanics and ask whether they are consistent with RQI.

P. Alsing A Quantum Optical Model for Unitary Black Hole Evaporation without Firewalls

J. Louko TBA

PANEL SPEAKERS

R. Mann Entanglement Extraction Near Black Holes

A. Kempf Replacing rods and clocks by the Feynman rules

E. Martin-Martinez Relativistic Quantum Optics: The theory of light-matter interaction from a relativistic perspective

J. Leon TBA

B.L. Hu Some issues of fundamental interest in RQI besides the holographic entanglement entropy

CONTRIBUTED TALKS

Aida Ahmadzadegan Exploring the boundaries of  multipartite quantum communication

Abstract: In this work we explore the boundaries of multipartite quantum communication through quantum fields using Unruh-DeWitt detectors. We use these detectors as quantum signaling devices which can couple to the field along the sender's and receiver's worldlines, and find the conditions under which the quantum field attains the maximal information carrying capacity. Ultimately we point out a number of applications that could be advanced using this improved communication method.

Alexander R. H. Smith Quantizing time: Interacting clocks and systems

Abstract: Motivated by the problem of time in quantum gravity, the conditional probability interpretation (CPI) of time posits that time evolution emerges from entanglement shared between a clock and system of interest, the joint state of which does not evolve with respect to a background time. After reviewing the CPI, I will present a generalization which allows for an interaction coupling the clock and system — we should expect such a coupling when the gravitational interaction between the clock and system is taken into account. I will demonstrate how such clock/system interactions result in a time-nonlocal modification to the Schrödinger equation and discuss the ensuing consequences. I will also comment on how the CPI may be extended to relativistic scenarios such as a particle moving through curved spacetime and quantum field theory.

Allison Sachs Entanglement Harvesting with Bosons and Fermions: is entanglement divergent?

Abstract: We will discuss entanglement harvesting with Uhruh DeWitt (UDW) detectors in the context of Fermionic fields.  In particular, we will focus on comparing entanglement harvesting with fermionic fields to its bosonic scalar counterparts: the usual linear-coupled UDW detector or a UDW detector coupled quadratically either to  a real or complex field. We will also discuss persistent divergences in quadratic UDW detector models revealed in previous literature and present novel techniques to regularize them.

Dennis Raetzel Optical resonators in curved spacetime

Abstract: There is an ever growing number of proposals for high precision experiments to measure gravitational effects, from simple Newtonian gravity to gravitational waves and even precision tests of general relativity (GR). In particular, more and more researchers from the fields of quantum optics and quantum opto-mechanics are becoming interested in GR and propose metrological experiments. Usually, such proposals rely heavily on a notion of length. However, in GR, as coordinates have no physical meaning, there is no unique concept for the length of a matter system.

Fabienne Schneiter The gravitational field of a laser beam

Abstract: In this talk, I present our recent work on the gravitational field of light in a focused laser beam, modeled as a solution to Maxwell's equations perturbatively expanded in the beam divergence. Using this approach, wave properties of light, such as diffraction, are taken into account that have been neglected in earlier studies. Interesting features of the gravitational field of laser beams become apparent: frame-dragging due to the intrinsic angular momentum of light; the deflection of parallel co-propagating test beams of light that overlap with the source beam.

We can expect the gravitational field of light to be extremely weak. However, advancements in sensor technology for oscillating gravitational fields may enable the detection of the effect in the future. Certainly, laser beams would be the suitable sources for such experiments. Therefore, it is important to gain detailed knowledge of the gravitational properties of laser beams. Independent of any experimental consideration, the properties of light are of general interest to the gravity community. In particular, the properties of light are premises in the foundations of modern physics: they were used to derive special and general relativity and are the basis of the concept of time and causality in many alternative models. Studying the back-reaction of light on the gravitational field could give new fundamental insights to our understanding of space and time as well as classical and quantum gravity.

Igor Pikovski Gravitational coupling to composite quantum systems

Abstract: The interplay between low-energy quantum physics and general relativity offers a variety of phenomena that shed light on some fundamental aspects of the two theories, and that may be probed in experiments. Here I will discuss how the dynamics of composite quantum systems is affected by the gravitational coupling beyond the Newtonian limit, and how the gravitational mass emerges for composite systems -- resolving an old controversy in general relativity.Bloch Oscillations in the Early Universe

Jason Pye Lorentz-Covariant Generalised Uncertainty Principles

Abstract: It is widely believed that combining the uncertainty principle with gravity will induce an effective minimum length scale. A key step in understanding quantum gravity is to find a consistent description for such a minimum length structure. A particular challenge is to specify a minimum length scale in a coordinate-independent manner so that covariance is not broken. Here we examine a class of Lorentz-covariant generalisations of the uncertainty principle which provides an effective low-energy model for such a Lorentz-invariant minimum length. We show how this modification leads to a kind of covariant bandlimitation of quantum field theory.

Jose de Ramón The Unruh effect without thermality

Abstract: We show that uniformly accelerated detectors can display genuinely thermal features even if the Kubo-Martin-Schwinger (KMS) condition fails to hold. These features include satisfying thermal detailed balance and having a Planckian response identical to cases in which the KMS condition is satisfied. In this context, we discuss that satisfying the KMS condition for accelerated trajectories is just sufficient but not necessary for the Unruh effect to be present in a given quantum field theory. Furthermore, we extract the necessary and sufficient conditions for the response function of an accelerated detector to be thermal in the infinitely adiabatic limit. This analysis provides new insights about the interplay between the KMS condition and the Unruh effect, and a solid framework in which the robustness of the Unruh effect against deformations of quantum field theories (perhaps Lorentz-violating) can be answered unambiguously.

Marco Letizia

Algebraic aspects of quantum fields in causal sets and entanglement entropy

Abstract: In this talk I will discuss some algebraic properties of two classes of quantum scalar fields living in a Lorentz invariant discrete background described by a causal set. In particular I will show how certain features of these models affect the behavior of the entanglement entropy, its divergences and the emergence of the area-law. Finally, I will make a comparison with similar computations carries out in other frameworks where a fundamental scale of quantum gravitational origin acts as a regulator.

Maria Papageorgiou Impact of relativity on localizability and vacuum entanglement

Abstract: One of the most curious aspects of relativistic quantum theories is that notions of localizability cannot be maintained, and there is no primary notion of a spatial wave function of a particle as in non-relativistic quantum mechanics. In this talk I will first review the issue of localizability in quantum field theory, and then propose how it can be addressed operationally. Then I will discuss a quantum field theoretic construction of a delocalized 'cat state', namely a one-particle state in superposition of different locations. It is not clear how such a state couples to gravity, since the semiclassical approach breaks down even for single particle states. I will investigate how one can probe such a state in the context of quantum field theory on curved spacetime.

Nadine Stritzelberger Towards a diffeomorphism-invariant formulation of gravity

Abstract: For the purpose of quantizing gravity, that is, quantizing the geometric degrees of freedom of a 3+1 dimensional Lorentzian manifold, it would be desirable to find a diffeomorphism-invariant reformulation of general relativity. The discipline of spectral geometry could help achieve this goal, as it is concerned with the extent to which the metric (and hence the curvature) of a manifold can be reconstructed from spectra of differential operators on the manifold, which are invariant under diffeomorphisms. We show how to reconstruct the geometric degrees of freedom of 1+1 dimensional Lorentzian and Riemannian manifolds from the spectrum of the d'Alembert operator.We discuss how to invert the highly non-linear map from metrics to spectra using Lagrange inversion.

Nitica Sakharwade A toy model for quantum causality in finite topological spaces

Abstract: In the quest for quantum gravity Hardy [1] suggests the radical aspects of quantum physics (probabilistic nature) and relativity (dynamic causality) would manifest together. In the recent years, this has led to an active study of causally neutral formulations through many approaches including the causaloid, quantum combs, process matrices and quantum conditional states. More particularly this has led to the study of indefinite causal structures, that allow for perplexing phenomenon such as the quantum switch to occur, and it is a difficult matter to interpret indefinite causal structures. In this work, we present a toy model set in finite topological spaces that have a natural causal structure emerging from its topology. In the setting of this toy model, we study indefinite causal structures that emerge from simple operational rules. We reproduce a version of the quantum switch and more such curious possibilities in this toy model and attempt to interpret these. The hope is to help shed some light on the study of indefinite causal structures.

Sofia Qvarfort Gravimetry through non-linear optomechanics

Abstract: Many quantum systems have been used for measuring gravitational acceleration to date, such as atom interferometers and on-chip BECs. In this work, we propose a new method for measurements of gravitational acceleration using a quantum optomechanical system. As a proof-of-concept, we investigate the fundamental sensitivity for a cavity optomechanical system for gravitational accelerometry, where the phase of the optical output of the cavity encodes the gravitational acceleration $g$. We show that the optimal measurement of $g$ is a homodyne measurement, and we predict a fundamental sensitivity of $\Delta g = 10^{-15} $ ms$^{-2}$ for currently achievable optomechanical systems which could, in principle, surpass the best atomic interferometers even for low optical intensities. In my talk, I will describe the methods used to compute this sensitivity and briefly discuss the experimental conditions that need to be met in order to realise this scheme.

Valentina Baccetti Information loss paradox: General features of evaporating shell collapse, and considerations of the semiclassical Einstein equation approach

Abstract: Analysis of the causal structure of collapse and evaporation process and detailed calculations lead us to consider the effects of black hole radiation starting prior to the final stage of collapse. Its precise form is still controversial, but its existence number of general conclusions about evolution of the collapsing bodies.  Starting from a massive thin shell in spherically-symmetric spacetime we show that if a non-zero radiation flux is perceived by a distant observer the shell remains at a certain sub-Planckian distance from the Schwarzschild radius. This distance depends only on the shell’s mass and evaporation rate. Moreover, a collapsing massive thin shell might become null in a finite proper time. To enable these results the metric should satisfy certain regularity requirements that are shown to be necessary if the semiclassical Einstein equations lead to a finite value of the Ricci scalar.  Horizon avoidance for shells can be extended to horizon avoidance in general spherically-symmetric collapse. Without the event horizon the paradox is gone, but many important conceptual and observational question just become more interesting.

Flaminia GiacominiQuantum mechanics and the covariance of physical laws in quantum reference frames

Abstract: In physics, every observation is made with respect to a frame of reference. Although reference frames are usually not considered as degrees of freedom, in all practical situations it is a physical system which constitutes a reference frame. Can a quantum system be considered as a reference frame and, if so, which description would it give of the world? The relational approach to physics suggests that all the features of a system —such as entanglement and superposition— are observer-dependent: what appears classical from our usual laboratory description might appear to be in a superposition, or entangled, from the point of view of such a quantum reference frame. In this work, we develop an operational framework for quantum theory to be applied within quantum reference frames. We find that, when reference frames are treated as quantum degrees of freedom, a more general transformation between reference frames has to be introduced. With this transformation we describe states, measurement, and dynamical evolution in different quantum reference frames, without appealing to an external, absolute reference frame. The transformation also leads to a generalisation of the notion of covariance of dynamical physical laws, which we explore in the case of ‘superposition of Galilean translations’ and ‘superposition of Galilean boosts’. In addition, we consider the situation when the reference frame moves in a ‘superposition of accelerations’, which leads us to extend the validity of the weak equivalence principle to quantum reference frames. Finally, this approach to quantum reference frames also has natural applications in defining the notion of the rest frame of a quantum system when it is in a superposition of momenta with respect to the laboratory frame of reference.

Tobias Westphal TBA

FLASH TALKS+POSTER

Aleksandra Dimić  Quantum switch in spacetime

Abstract: The realization of indefinite causal order, a theoretical possibility that even the causal order of events in spacetime can be subjected to quantum superposition, apart from its general significance for the fundamental physics research, would also enable quantum information processing that outperforms protocols in which the underlying causal structure is definite. In this paper, we propose different realizations of a simple case of indefinite causal order - the "quantum switch". Furthermore, we show that by using the "double quantum switch" one can realize entangled causal structures.

Bekir Baytas  Gluing polyhedra with entanglement in loop quantum gravity

Abstract: In a spin-network basis state, nodes of the graph describe un-entangled quantum regions of space, quantum polyhedra. We show how entanglement between intertwiner degrees of freedom enforces gluing conditions for neighboring quantum poly- hedra. In particular we introduce Bell-network states, entangled states defined via squeezed vacuum techniques. We study correlations of quantum polyhedra in a dipole, a pentagram and a generic graph. We find that vector geometries, structures with neigh- boring polyhedra having adjacent faces glued back-to-back, arise from Bell-network states. We also discuss the relation to Regge geometries. The results presented show clearly the role that entanglement plays in the gluing of neighboring quantum regions of space.

Ding Jia Quantum field theory with indefinite causal structure

Abstract: There are several reasons for the general presence of indefinite causal structure in nature: 1) Quantum indefiniteness of matter coupled to gravity. 2) Operational definitions of events by signal arrival times, which exhibit fundamental fluctuations. 3) All dynamical variables exhibit uncertainties in quantum theory, and

causal structure is dynamical in GR. 4) Laboratories setups to generate indefinite causal structure.

To investigate the impact of indefinite causal structure on field theoretic effects such as Hawking and Unruh effects, a framework to study quantum field theory with indefinite causal structure is needed. We present such a framework. According to this proposal, ordinary field correlation functions are too limited to describe nature and should be "doubled-up".

Erickson Tjoa   Resonance and Weak Equivalence Principle in Cavity QFT

Abstract: We present further studies on the response of an inertial Unruh-DeWitt detector traversing through an accelerating rigid cavity and its distinguishability from an accelerating detector in static cavity in presence of Klein-Gordon field. The response of the detector is obtained with respect to (a) single-mode excited field state and (b) coherent field state for both massless and massive scalar fields in (1+1) dimensions. We discuss the role of resonance between the excited mode frequency and the gap of the detector in providing non-local information and its connection to the weak equivalence principle.

Francisco Pipa  The effects of entanglement between gravity and matter on the motion of localized massive particles

Abstract: We derive an effective equation of motion for a pointlike particle in the framework of quantum gravity from simple basic assumptions. The geodesic motion of a classical particle can be deduced by coupling a classical field theory to general relativity. We use a similar method to obtain an effective equation of motion, starting from an abstract quantum gravity description. We find that entanglement between gravity and matter leads to modifications of the geodesic trajectory, mainly because of nonzero overlap terms between gravity-matter coherent states. Lastly, we discuss a possible violation of the weak equivalence principle due to the nongeodesic motion.

Friedrich Koenig Spontaneous emission in optical analogue gravity systems

Abstract: Quantum fluctuations in curved space-time cause the emission of particles.  Under certain conditions, event horizons can create one-way doors, as in the case of black holes. Here we investigate and demonstrate the role of event horizons for the

production of entangled pairs in a dispersive analogue system. We find that horizons lead to an order of magnitude increase in the pair production, strong and purified quantum correlations, and a characteristic shape of the photon emission spectrum.

We consider a moving refractive index perturbation in an optical medium, which exhibits optical event horizons.  Based on the field theory in curved space-time we formulate an analytical method to calculate the scattering matrix that completely describes mode coupling leading to the emission of photon pairs in various configurations.  We quantify the emission by the emission spectrum and the spectrally resolved photon number correlations, as they would be observed in the laboratory.  Moreover, we apply our method in a case study, in which we consider a moving refractive index step in bulk fused silica. We calculate the emission flux in the moving frame as well as in the laboratory frame.   The flux from horizons is particularly enhanced and carries a signature spectral shape.   In both frames, we observe significant spectral quantum correlations between modes of opposite norm, evidence of their vacuum origin.  If the modes form horizons, the correlation with the partner photon mode increases and approaches unity.  These methods and findings pave the way to the observation of particles from the event horizon in optical systems.  Furthermore, they will be relevant in a number of other optical and non-optical systems exhibiting horizons.

Hui Wang  Exploring the Unruh effect for one to many oscillating detectors; circuit QED and nanomechanical analogues

Abstract: We consider N>1 relativistic, oscillating centre of mass photon detectors modeled as harmonic oscillators that are coupled to a common cavity mode. Including detector and cavity loss, we solve for the quantum dynamics, which is completely specified by the first and second moments of the N detector and cavity quadrature coordinates. Under certain resonant conditions between the various characteristic frequencies and relative phases between the oscillating detectors, we observe significant enhancements in the average, steady state detectors' and cavity photon numbers. We also characterize the correlations between the detectors and cavity mode using the logarithmic negativity entanglement measure. Through a series of approximations we map the relativistic N-detector cavity system onto a non-degenerate parametric amplifier model which affords accurate, analytical expressions for the first and seconds, as well as suggests feasible analogue, microwave circuit and nanomechanical realizations.

Laura Henderson 

Entanglement Harvesting in a Geon Spacetime

Abstract: We study the effects of an RP2 geon on the entanglement harvesting protocol, a pair of Unruh-DeWitt (UDW) become entangled through interactions with a quantum field, and make comparisons to the BTZ black hole. The detectors are stationary ant located at different radii from the horizon and the field is the  Hartle-Hawking vacuum of a conformally coupled massless scalar field. We find that less entanglement can be harvested in a geon spacetime then in the corresponding black hole spacetime, and this difference is dependent on the mass of the black hole. We also find, that like the black hole, the geon inhibits entanglement harvesting near the horizon; however the region of “sudden death” of entanglement harvesting is at a larger radius in the geon spacetime.

Marko Vojinovic  Timelike nonlocality and causality in quantum gravity

Abstract: We will discuss the relationship between the notion of timelike nonlocality and the notion of entangled causal order, from the points of view of classical and quantum gravity. In particular, we will argue that timelike nonlocality is well defined and possible in classical background spacetimes (such as Minkowski or Schwarzschild). On the other hand, the entanglement of causal orders is not well defined in such backgrounds. Nevertheless, entangled causal order can indeed be defined --- and can only be defined --- in the context of quantum gravity. We will demonstrate an explicit realization on a toy-example of the Regge quantum gravity model.

Maxime Jacquet The Hawking effect in dispersive media

Abstract: The Hawking effect of spontaneous emission at the horizon of black holes is one of the outstanding predictions of quantum field theory. However, because of its ultra-low temperature, observing it in the astrophysical context is an inconceivable feat. Fortunately, it is possible to create event horizons for waves in media, which renders the observation of this quantum emission doable. If the initial proof of this analogy between wave motion on curved spacetimes and the kinematics of waves in media was derived without accounting for the effect of dispersion, it has since been realised that the influence of the latter is actually key to enabling the experimental creation of analogue horizons. Here, we show in which regimes of dispersion the Hawking effect may really be observed in an optical-analogue scheme. We consider the limits and epistemology of the analogy to the astrophysical system thus drawn. We

propose an onthological shift, whereby the necessity for experiments to operate in dispersion regimes in which the analogy cannot be mathematically derived is acknowledged. This will aid bridging from the theoretical to the experimental realms.

Meenu Kumari Symmetric extensions of process matrices

Abstract: We define the symmetric extension of process matrices in analogy with the symmetric extension of quantum states. Further, we investigate whether the causal inequalities for process matrices are monogamous or not. Monogamy of a causal inequality would imply that at most only one of the three bipartite reduced process matrices of any tripartite process matrix can violate the corresponding causal inequality. This would have implications for determining whether or not a bipartite process matrix will violate a causal inequality contingent of the existence of its symmetric extension. This work is done in collaboration with Robert Mann, Fabio Costa and Shohini Ghose.

Nikola Paunkovic  Gauge protected entanglement between gravity and matter

Abstract: We show that gravity and matter fields are always entangled, as a consequence of the local Poincaré symmetry. First, we present a generic argument, applicable to any particular theory of quantum gravity with matter, by performing the analysis in the abstract nonperturbative canonical framework, demonstrating that the scalar constraint allows for only the entangled states as the physical ones. Also, within the covariant framework, we show explicitly that the Hartle-Hawking state in the Regge model of quantum gravity is necessarily entangled. Our result is potentially relevant for the quantum-to-classical transition, taken within the framework of the decoherence programme: due to the symmetry requirements, the matter does not decohere, it is by default decohered by gravity. Generically, entanglement is a consequence of interaction. This new entanglement could potentially, in form of an “effective interaction”, bring about corrections to the weak equivalence principle, further confirming that spacetime as a smooth four-dimensional manifold is an emergent phenomenon. Finally, the existence of the symmetry-protected entanglement between gravity and matter could be seen as a criterion for a plausible theory of quantum gravity, and in the case of perturbative quantisation approaches, a confirmation of the persistence of the manifestly broken symmetry.

Petar Simidzija A general no-go theorem for entanglement extraction

Abstract: The extraction (or harvesting) of entanglement by Unruh-DeWitt particle detectors from a quantum field can tell us a lot about the spacetime on which the field lives [1,2]. However, there exist setups in which entanglement harvesting is not possible. Namely:i)           Perturbatively, identical degenerate detectors cannot harvest spacelike entanglement from the vacuum [3].ii)     Non-perturbatively, Dirac-delta coupled detectors cannot harvest entanglement from coherent field states [4].We consider the more general setup of two targets attempting to extract entanglement by locally coupling to a bipartite source. We derive a necessary condition on the system’s Hamiltonian which allows for entanglement extraction. Our result immediately generalizes the no-go theorems i) and ii) to read:i)           Non-perturbatively, any degenerate detectors cannot harvest spacelike entanglement from any field state.ii)     Non-perturbatively, Dirac-delta coupled detectors cannot harvest entanglement from any field state.Finally, our work also provides insight into the role of communication in entanglement extraction processes, allowing us to distinguish between genuine entanglement extraction and communication-assisted entanglement generation.

[1] G. V. Steeg and N. C. Menicucci (2009).[2] E. Martin-Martinez, A. R. H. Smith, D. R. Terno (2016).[3] A. Pozas-Kerstjens, J. Louko, E. Martin-Martinez (2017).[4] P. Simidzija and E. Martin-Martinez (2017).

Qidong Xu    Quantum dynamics of a falling particle in a thermal graviton bath

Abstract: Using a perturbative quantum field description of Einstein gravity coupled to a massive scalar field, we investigate the quantum dynamics of an initially localized single-particle excitation under the combined influence of a weak, static uniform gravitational field and a thermal graviton bath. Such conditions approximately model the gravitational environment in a terrestrial laboratory experiment. The analysis centres on evaluating the equal time, two-point correlation function for the massive scalar field as a means to extract observable quantities such as the local detected particle number distribution. We investigate the effect on the spreading of the particle

number distribution due to the presence of the thermal graviton bath as the particle is falling and infer the effects of gravitational decoherence.

Richard Lopp     The signature of accelerated detectors in cavities

Abstract: We examine if the usual approximations of Quantum Optics are valid to study the Unruh effect in a cavity - as these approximations have been applied in past literature for those scenarios. Therefore, we consider the behaviour of an accelerated Unruh-DeWitt particle detector interacting with a quantum scalar field whilst travelling through a cavity in 3+1D. We thereby model a simplified version of the light-matter interaction between an atom and the electric field. We characterize the relativistic and non-relativistic regimes, and show that the energy is not merely localized in a few number of field modes in general, rendering it impossible to employ the single mode approximation. Furthermore, we find that overall neither the massless nor the massive scalar field of a 1+1D theory is a satisfying approximation to the effective 1+1D limit. The ultimate objective will be to study if the bombardment of the cavity with a stream of accelerated atoms results in the accumulation of a significant signature in the field characteristic of the Unruh effect, avoiding thereby the need for thermalisation of the atoms.

Robert Jonsson  Energy cost of entanglement extraction from Klein-Gordon vacuum

Abstract: The phenomenon of vacuum entanglement has sparked a fascinating range of research. A topic which gained particular attraction is how to operationally extract entanglement from quantum fields, e.g., through entanglement harvesting. Only most recently a central question in this context was highlighted [1]: How much energy does it cost to extract of entanglement from a quantum field? Here, we address this question for localised modes in a Klein-Gordon field. Combining and extending methods from [2] and [3], we study the correlations and the binding energy shared by local modes and their partner modes.

Joint work with T. Farrelly, D. Bondarenko and C. Beny.

[1] Beny, Cedric, Christopher T. Chubb, Terry Farrelly, and Tobias J. Osborne. “Energy Cost of Entanglement Extraction in Complex Quantum Systems.” ArXiv:1711.06658 [Quant-Ph], November 17, 2017. http://arxiv.org/abs/1711.06658.[2] Zych, Magdalena, Fabio Costa, Johannes Kofler, and Časlav Brukner. “Entanglement between Smeared Field Operators in the Klein-Gordon Vacuum.”

Physical Review D 81, no. 12 (June 24, 2010): 125019. https://doi.org/10.1103/PhysRevD.81.125019.[3] Hotta, M., R. Schützhold, and W. G. Unruh. “On the Partner Particles for Moving Mirror Radiation and Black Hole Evaporation.” ArXiv:1503.06109 [Gr-Qc, Physics:Quant-Ph], March 20, 2015. http://arxiv.org/abs/1503.06109.

Sahar  Sahebdivan  Gravitational Scattering off a Spatial Cat State: The effect of spatial superposition of mass on the structure of space-time in the micro scale

Abstract: We are exploring the feasibility of observing non-classical features of gravity in a linearized, low-energy regime, via a quantum optomechanics experiment. If gravity has an underlying quantum nature, there should be a corresponding observable which holds the most fundamental quantum characteristics such as superposition principle and entanglement. We are investigating a new dynamical scheme, gravitational quantum regime, in which the source of gravity is a large quantum particle, whose spatial degree of freedom (center of mass) is subject to the quantum superposition. In a Gedankenexperiment, a test particle is gravitationally scattered off a quantum Nanoparticle in a double-slit potential, hypothetical entanglement or Q-superposition of the fields is investigated. We associate such a gravitational quantum scatterer with an additional non-local term in the Laplace operator. Accordingly, we expect a deviation in the dynamic of the test particle due to the quantum superposition of the gravitating source mass, which shows up in the interferometric outcome of the experiment. Such a phenomenological investigation gives us an understanding of how the axiom of quantum superposition and uncertainty principle are interpolating into the construction of space-time in microscale. Moreover, this proposal would be an attempt to testify or falsify the objectivity of quantum superposition principle directly.

Sebastian Kish Quantum Metrology in the Kerr Metric

Abstract: A surprising feature of the Kerr metric is the anisotropy it causes in the velocity of light. The angular momentum of a rotating massive object causes co- and counter-propagating light paths to move at superluminal and subluminal velocities, as observed from a distance. Based on this effect we derive ultimate quantum limits for the measurement of the rotation parameter “a” using Gaussian probe states. As a possible implementation we propose a radial Mach-Zender interferometer to isolate and measure the direction dependent time delay in the Kerr metric. We also investigate the physics of this situation by framing the problem in three different

scenarios. Namely, we can show that a time delay from rotation in an interferometric setup arises purely from the geometry of light rays in a rotating inertial reference frame. We can thus apply the same line of reasoning to stationary observers above a rotating mass in the Kerr metric and to the so-called Kerr "ring-riders" that are locally in a flat space-time.

Shih-Yuin Lin Estimating field states at large scales by an accelerated local observer

Abstract: The worldline of a uniformly accelerated local observer in Minkowski space is restricted in a Rindler wedge, where the observer can arrange experiment repeatedly in principle, and the Cauchy problem for quantum fields in the Rindler wedge is well defined. However, the observer is not restricted to see Rindler particles since the observer can receive the signals from the events behind the illusive horizon, though the observer cannot manipulate any physical process there. With some additional information and assumptions, therefore, the observer could estimate the field state defined on a spacelike hypersurface crossing the illusive horizon.

Wan Cong  A Quantum Cavendish Experiment 

Abstract: If the quantum evolution of gravitationally interacting masses can be described by the usual Schrödinger equation, it is possible for spatially separated masses to become entangled via this interaction [1,2]. On the other hand, less or no entanglement will be observed in some alternative quantum theories such as the Diosi-Penrose collapse model [3,4]. We consider a thought experiment reminiscent of the Cavendish set-up in the quantum regime and ask if entanglement between masses can be observed in this model. The experiment makes use of the creation of non-classical states of two mechanical oscillators using radiation pressure similar to the scheme proposed in [5].  We compute the shift in the visibility pattern of the cavity photons due to the Newtonian gravitational interaction between the oscillators and compare this shift with what is expected from other gravitational decoherence models.

Yasusada Nambu  Harvesting Large Scale Entanglement in de Sitter Space with Multiple Detectors

Abstract: We consider entanglement harvesting in de Sitter space using a model of multiple qubit detectors. We obtain the formula of the entanglement negativity for this system. Applying the obtained formula, we find that it is possible to access to the entanglement on the super horizon scale if sufficiently large number of detectors are

prepared. This result indicates the effect of the multipartite entanglement is crucial for detection of large scale entanglement in de Sitter space.

Akira   Matsumura Large Scale Quantum Entanglement in de Sitter Spacetime

Abstract: We investigate quantum entanglement between two symmetric spatial regions in de Sitter space with the Bunch-Davies vacuum.  As a discretized model of the scalar field for numerical simulation, we consider a harmonic chain model. Using the coarse-grained variables for the scalar field, it is shown that the multipartite entanglement on the super horizon scale exists by checking the monogamy relation for the negativity which quantifies the entanglement between the two regions. Further, we consider the continuous limit of this model without coarse-graining and find that non-zero values of the logarithmic negativity exist even if the distance between two spatial regions is larger than the  Hubble horizon scale.

Keith Kai-Chung Ng  New techniques for entanglement harvesting in flat and curved spacetimes

Abstract: We present a new technique for computing entanglement harvesting with Unruh-DeWitt particle detectors. The method is particularly useful in cases where analytic solutions are rare and the Wightman function is known only via its mode expansion for which numerical integration can become very expensive. By exploiting the conjugate symmetry of the Wightman function, we may split the integral into parts dependent on the commutator and anti-commutator of the field. In cases where the commutator vanishes, such as spacelike separation, or timelike separation if the strong Huygens principle holds, we then show that the entangling term of the bipartite density matrix can be expressed in terms of the much simpler mutual information term. For the vacuum state, this can be translated into a simple Fourier transform, and thus a single sum over modes, simplifying the procurement of closed expressions. We demonstrate this for Minkowski space, finding an analytical solution where none was previously known.

Pascal Fries   Renormalizing quantum field theories on wavelet lattices   

Abstract: A discrete wavelet transform and its corresponding multi resolution analysis provide a natural framework for the regularization of quantum field theories. In this framework, I show how the renormalization group flow of a continuum theory can be

implemented on the lattice by means of a cMera-like Ansatz. Holographic aspects of he construction are discussed.

POSTERS

André Stefanov  Broadband energy entangled photons and their potential for space applications

Abstract: Photon are the most natural choice to distribute entanglement among distant partners, as for instance in entanglement-based space experiments. In the present contribution we focus on energy entangled states produced by spontaneous parametric downconversion, where the spectrum of the individual is photons much broader than the one of the pump photon. As advantages, they offer a flux as high as $10^{12}$ pairs/s, together with an entanglement content of each pair as large as 15 ebit. The state is intrinsically of very large dimension and thus useful for advanced quantum information protocols. Additionally, a regime can be accessed where measurements with femtosecond time resolution are possible with continuous light. The manipulation of such states requires specific techniques inspired form ultrafast optics. In order to make use of this large entanglement, a spectrum manipulation stage is used. Additionally, because of the short temporal correlations, the coincidence detection should be performed with a time resolution much shorter than currently accessible with single photon counters. We therefore use an ultrafast optical coincidences scheme, based on non-linear process in a crystal.

Dimitrios Moustos Unruh-DeWitt detectors as open quantum systems

Abstract: We treat an Unruh-DeWitt qubit detector as an open quantum system, with a scalar or an electromagnetic field playing the role of the environment. We calculate the evolution of the reduced density matrix invoking neither the Markov nor the Rotating Wave approximation. We provide a detailed characterization of all regimes where non-Markovian effects are significant. We argue that the most stable  characterization of acceleration temperature  refers to the late time   behavior of the detector because interaction with the field vacuum brings the qubit to a thermal state at the Unruh temperature. In contrast, the early-time transition rate, that is invoked in most discussions of acceleration temperature, 

does not exhibit a thermal behavior when non-Markovian effects are taken into account. We discuss the implications of our results for the measurement of theUnruh effect and for the study of entanglement dynamics in multi-qubit systems.

Giulia Rubino  Experimental Entanglement of Temporal Orders

Abstract: The study of causal relations, a cornerstone of physics, has recently been applied to the quantum realm, leading to the discovery that not all quantum processes have a definite causal structure. Here, we present the first theory-independent experimental demonstration of entangled temporal orders, resulting in a process with an indefinite causal structure. While such processes have previously been observed, these observations relied on the assumption that experimental operations and systems are described by quantum theory. This opens a ‘loophole’ wherein the observed process can be explained by an underlying theory with a definite causal structure. To circumvent this, we build a model attempting to describe experimental data using a large class of general probabilistic theories that are local and have a definite temporal order. We then experimentally invalidate this model by violating a Bell inequality. We therefore conclude that nature is incompatible with the theories requiring a local definite temporal order.

Helder Alexander Entanglement of self-interacting scalar fields in an expanding spacetime

Abstract: We evaluate self-interaction effects on the quantum correlations of field modes of opposite momenta for scalar $\lambda \phi^4$ theory in a two-dimensional asymptotically flat Robertson-Walker spacetime. Such correlations are encoded both in the von Neumann entropy defined through the reduced density matrix in one of the modes and in the covariance expressed in terms of the expectation value of the number operators for each mode in the evolved state. The entanglement between field modes carries information about the underlying spacetime evolution.

Kengo Maeda  Negative energy and entanglement entropy on the holographic wormhole solution

Abstract: We semi-analytically construct a four-dimensional asymptotically AdS spacetime for a thermal state living on a wormhole background by applying gradient expansion method. The bulk spacetime includes a topologically non-trivial vacuum AdS black hole in which two asymptotically planar black branes are glued together by

a hyperbolic black hole near the wormhole throat. We show that the null energy condition for the holographic stress energy tensor is violated near the throat in the low temperature state. We also calculate a holographic entanglement entropy of a surface on the throat that splits the whole boundary space on the wormhole background into two. Interestingly, the holographic entanglement entropy diverges in the zero temperature limit, due to the existence of the non-vanishing black hole entropy of the hyperbolic black hole. We also construct such wormhole solutions in a full numerical simulation by de Turck method.

Koji Yamaguchi   Theorems on Entanglement Typicality in Non-equilibrium Dynamics

Abstract: The notion of typicality in statistical mechanics is essential to characterize a macroscopic system. An overwhelming majority of the pure state looks almost identical if we neglect macroscopic non-local correlations, suggesting that thermal equilibrium is the collection of the typical properties. Quantum entanglement, which characterizes a non-local correlation, also has a typical behavior in equilibrium systems. However, it remains elusive whether there is a typical behavior of entanglement in dynamical non-equilibrium systems. To investigate the typicality, we consider a situation where a system in a pure state starts to share entanglement with its environment system because of the interaction among them. Assuming the initial state is randomly chosen from an ensemble of pure states, a criteria for the typicality of the R\'enyi entropies is presented. In addition, it is analytically proven that the second R\'enyi entropy has a typical behavior in two cases. The first one is an energy dissipation process in a multiple-qubit system which is initially in a random pure state in an energy shell. Since the typical behavior is qualitatively the same as the prediction of the Page curve conjecture, it gives the first proof of the Page curve conjecture in a dynamical process. In the second case, the typicality is proven for any dynamics described by a multiple-product of a single-qudit channel when the system is initially in a pure state randomly chosen from the whole Hilbert space. This result shows that entanglement typicality is not a specific feature of energy dissipating processes.

Marc Holman   Quantum Gravity, Temporal Asymmetry and the Second Law of Thermodynamics

Abstract: Although it seems clear on conceptual grounds that proper gravitational degrees of freedom must somehow be assigned a physical entropy, while the laws of black hole mechanics even constitute ample evidence for the existence of a deep link between gravity and thermodynamics, a fundamental problem with attempts to explain

the origins of the second law of thermodynamics in terms of a cosmological boundary condition is that there is at present no well defined measure of gravitational entropy.After reviewing this situation in some depth and incorporating it into a wider perspective on the second law of thermodynamics and its origins, while also taking note of some well-known theoretical and conceptual caveats that thermodynamic reasoning in cosmology runs into, I will argue that a future theory of ``quantum gravity'' - i.e., a consistent physical theory that somehow contains both quantum theory and general relativity in appropriate limits - is exactly what is needed to properly address these difficulties.But this in fact cuts both ways and arguably the search for the very principles of a theory of quantum gravity should be strongly guided by the aim to properly account for the second law. As I will in addition argue, although the usual account of thermodynamic irreversibility in terms of a cosmological boundary condition proceeds on the premise of a time-reversible underlying dynamics, there are at least two important reasons to call into question such a premise. First, it has been shown that there is a crucial difference between quantum field theories formulated respectively on black hole and white hole backgrounds with respect to their behaviour at future null infinity. In particular, in the latter case, any initial state that is a direct product of a horizon state with a state at past null infinity, gives rise to pathological behaviour at future null infinity (in the form of infinite particle and energy fluxes).Second, there are strong reasons to think that owing to the existence of particle creation near black holes, quantum gravity allows for the evolution of pure states into mixed states and is therefore necessarily time reversal non-invariant.

Marco Rivera  CHSH inequality in the weak field approximation limit

Abstract: CHSH inequality in the weak field approximation limit: We study Bell tests for Franson and Hugging interferometers under a difference of gravitational potential between its arms. We feed both interferometers with particles, which act as clocks, and show how the gravitational field affects the CHSH inequality in this setup. We also calculate the logaritmic negativity of the Bell state generated inthose interferometers. Futhermore, we analyse the HOM effect for photons and massive particles in a modified Mach-Zehnder setup with two particles experiencing different gravitational potentials, which are later recombined using beam-splitter. We find that the HOM effect depends directly on the time dilations between arms of the  setup. Finally, we discuss the possible improvements to the detection of phase changes due to time dilation when using N particles.

Mohamed Farouk Ghiti Quantum Entanglement Of Boson-Antiboson pair creation in Non commutative Bianchi I space-time

Abstract: The Von Neumann Boson-antiboson pair creation quantum entanglement entropy (Q.E.) is studied. It is shown that its behavior is strongly dependent on the value of the noncommutativity θ parameter, k-modes frequencies and the structure as well as the anisotropy of the space-time. Thermodynamical properties and their relationship with Q.E. are also discussed.

Noureddine Mebarki  Spin entanglement states in a non commutative space-time

Abstract: The effects of the space-time non commutativity and curvature  on the spin entanglement of fermionic and bosonic bipartite quantum states system are studied in  a general static curved space-time. lt is shown that during the time evolution and depending on the various parameters of the system, one can always generate maximally entangled Bell's states. Behavior of the system near the black hole and crossing the event horizons are also discussed.

Philippe Allard Guérin   Observer-dependent locality of events in quantum causal structures

Abstract: The process matrix formalism [1] was invented to describe multipartite quantum correlations, without the assumption of a well-defined causal order. Certain correlations predicted by the formalism are incompatible with the assumption of a causal ordering of the events – these correlations violate causal inequalities. However, the formalism offers no clue as to how one might physically realise such acausal correlations. We attempt to understand these processes in a more physical way by making an explicit connection with certains aspects of the relativistic description of causality. We propose to associate to each event a "causal reference frame", and relate the reference frames of different events via a global consistency condition. We show that these assumptions allow one to recover the pure process formalism [2], and that the time-locality of events is reference-frame dependent. We study a new example of a non-causal process, and point out curious features in its causal reference frame description, which may explain why such a process lacks a physical realisation within known physics.

Roberto Pierini  Quantum key distribution in non inertial frames

Abstract: We investigate how relativistic acceleration of the observers can affect the performance of various quantum key distribution protocols for continuous variable states of localized wave packets.

Sang Eon  Park    Noisy quantum channel model for the retrieval of black hole information

Abstract: Noisy quantum channel model for the black hole final state is studied for the de Sitter spacetime. We have shown that the Hawking effects can be described by a noisy quantum channel model having a complete positive map with an operator sum representation. We also investigate the mutual information between Hawking radiation and infalling matter to measure the retrieval of black hole information. This model leads us to understand the non local correlation of black hole evaporation and more specific behavior of information recovery. We suggest that it would be possible to measure the scrambling of random unitary operation with proposed model.

Theodora Kolioni  The transition of quantum information of an open quantum system interacting with a quantum scalar field

Abstract: In this paper, we investigate the transmission of information through the environment between two widely separated quantum systems, modeled as harmonic oscillators. We focus on quantum Brownian motion models in which N separated oscillators interact with a quantum scalar field. We compute the solutions for the homogeneous equation of motion and the dissipation and noise kernel, of which is constructed the density matrix propagator of the system. We demonstrate that the Markovian approximation fails for this system. We explore the interplay between characteristic non-Markovian phenomena, such as memory effects and quantum correlations, and the quantum phenomena of superposition and entanglement.

Vyome Singh  Implementation of Scattering matrix formalism at optical analogues

Abstract: Any stationary scattering process is completly described by the scattering matrix, S. The scattering matrix relates the incoming states to the outgoing states. The scattering matrix formalism is used in many fields of physics such as quantum mechanics, optics, electronics and quantum field theory. In this poster we discuss different numerical ways to compute the S matrix to find a numerically stable and efficient way. We discuss the T-Matrix algorithm, S-Matrix algorithm [1] and the generalised scattering coefficients [2]. Performance and efficiency of each algorithm is analysed and presented. Analogue Optical Event horizons created by a pulse travelling in fiber were first proposed and demonstarted in 2008 [3]. Spontaneous emission have been studied in detail from a travelling refractive index step [4] but an in depth understanding of the strenght of emission from pulses have eluded us. Here, we implement the scattering formalsim at optical analogues created by pulse travelling in a fiber. We treat the pulse as a stationary scatterer and compute a corresponding scattering matrix describing the system. We have come up with general scattering matrix equation, which could be solved numerically in any mathematical software package. This would make it possible to calculate strength of sponataneous vacuum emission from the pulse. Our formalism is robust enough to be used in other possible scattering problems which encounter numerical instabilities and/or problems with convergence.

[1] D. Y. K. Ko and J. R. Sambles, "Scattering matrix method for propagation of radiation in stratified media: attenuated total reflection studies of liquid crystals," J. Opt. Soc. Am. A 5, 1863-1866 (1988)  [2] Weng Cho Chew, Waves and Fields in Inhomogeneous Media, IEEE press, 1995 [3] T.G. Philbin, C. Kuklewicz, S Robertson, S Hill, F Koenig, U Leonhardt,” Fiber-Optical Analog of the Event Horizon,” SCIENCE Vol 319, Issue 5868, 2008 : 1367-1370 [4] M. Jacquet and F. König: "Quantum vacuum emission from a refractive index front"   Phys. Rev. A 92, 023851 (2015)

Terry Farrelly Higher spin quantum walks and quantum simulations of physics

Abstract: Remarkably, very simple quantum walks give rise to relativistic dynamics in the continuum limit. To date, a lot of attention has been paid to quantum walks that become the Weyl and Dirac equations in the continuum limit, which offer an interesting possibility for simulations of physics on a quantum computer. Here, we introduce quantum walks leading to relativistic dynamics with higher spin in the continuum limit. Special cases include the familiar Weyl and Dirac walks, but we also

discuss other cases, including a spin one walk, which can be thought of as a photonic quantumwalk.

Warner Miller Quantum Information Geometry, Entanglement and Gravitation

Abstract: No elementary quantum phenomenon is a phenomenon until it is brought to close by an irreversible act of amplification. This Niels Bohr-inspired quantum tome of John Archibald Wheeler, together with the Principle of Complementarity, is at the very heart of Wheelers It-from-Bit framework. In this talk, we will explore entanglement networks within this information-centric approach. The quantum network we consider in this manuscript is a quantum multipartite state (pure or mixed) with varying degrees of entanglement. Observers examine the space of measured data from repeated experiments on a set of identically-prepared quantum states. We extend information distance measures based on Shannon's entropy and generalizes it to higher dimensions. We discuss the emerging geometry, its quantum information-based curvature and its relation to the curvature of spacetime.  Concrete examples will be provided.

Scott Todd Lorentz violation in sonically relativistic Compton scattering

Abstract: We explore a simple toy model of Compton scattering in an analogue-gravity setting. Specifically, we consider scattering of a phonon (sonically relativistic particle) off of a Newtonian particle and consider this interaction from the perspective of a hypothetical in-universe observer. Our prior work has shown that such observers, who construct clocks and rulers by exchanging phonons, would naturally perceive their universe to obey sonic special relativity with c = the speed of sound. The presence of a Newtonian scattering particle would break this symmetry -- at least from the perspective of the laboratory. We report on how this Lorentz violation appears to the in-universe observers. We also consider the relation of this work to Lorentz-violating extensions of the standard model of particle physics.

Bekir Can Lutfuoglu

Relativistic wave equation solutions with a  mixed scalar-vector generalized symmetric Woods-Saxon potential

Abstract: We investigate the solutions of Klein-Gordon and Dirac equation with the presence of both generalized symmetric Woods-Saxon vector and scalar potential. In one spatial dimension, we obtain the bound state and scattering solutions in terms of hypergeometric and Heun functions   for spin symmetric or pseudo-spin symmetric cases.

Sho Onoe Particle production and apparent decoherence due to an accelerated time-delay

Abstract: We study the radiation produced by an accelerated time-delay acting on the left moving modes. Through analysis via the Schrodinger picture, we find that the final state is a two-mode squeezed state of the left moving Unruh modes, implying particle production. We analyse the system from an operational point of view via the use of self-homodyne detection with broad-band inertial detectors. We obtain semi-analytical solutions that show that the radiation appears decohered when such an inertial observer analyses the information of the radiation from the accelerated time-delay source. We make connection with the case of the accelerated mirror. We investigate the operational conditions under which the signal observed by the inertial observer can be purified.

Adamantia Zampeli Superselection rules in quantum cosmology

Abstract: In this presentation, I will discuss the existence of superselection rules in canonical quantum cosmology. In particular, I will show that the canonical quantization of cosmological systems by the imposition of all the generators of the time dependent automorphisms inducing diffeomorphisms on the wave function leads to superselection rules. I discuss further the implications on the interpretation of the wave function and the formulation of a quantum mechanical formalism in this context.

Navya Gupta Higher Order Corrections to the Entanglement Entropy for a Two-Dimensional Conformal Field Theory

Abstract: Entanglement entropy (EE) is a measure of correlations between two subsystems in a larger quantum system. The EE for a conformal field theory (CFT) with a holographic dual reveals interesting characteristics of the bulk spacetime. In this ongoing work, we use an extended saddle point analysis and the Rindler map to compute higher order corrections to the EE for a two dimensional CFT, going beyond previously computed logarithmic corrections. Our current goal is to uncover the universal structure underlying these higher order corrections, and their implications on entanglement thermodynamics.

Nikolaos Kollas Resource theory of projective quantum measurements constrained by physical symmetries.

Abstract: We introduce a new measure of quantum resources associated with the maximum amount of available information obtained by a projective measurement when the set of allowed measurements is constrained by a physical symmetry. By applying it to a bipartite quantum state we show how this approach is equivalent to known measures of quantum resources such as entanglement and quantum discord. We also provide examples of unipartite and continuous systems for which a subsystem partition is no longer available and demonstrate that even in this case there is a small amount of inaccessible information residing in the state.Irismar da Paz Gouy Phase and Fractional Orbital Angular Momenta

Abstract: An electron in a paraxial beam projects a half a quantum unit of spin angular momentum parallel or anti-parallel to the beam axis. Here, an exact solution to the Dirac equation is presented for a tightly focused non-paraxial Gaussian electron beam which includes the Gouy phase. This diffraction limited solution agrees with similar recent Bessel beam solutions in predicting that tight focusing can lead to the partial conversion of spin angular momentum into fractional orbital angular momentum. In contrast to earlier Bessel beam solutions our electron beam solution present a relationship between Fractional Orbital Angular Momentum and Gouy phase.