Conference

Displaying 3133 - 3144 of 5051

Is there a MesoScale in Quantum Gravity? Is it a Non-Locality Scale?
- Laurent Freidel Perimeter Institute for Theoretical Physics
- Stefano Liberati SISSA International School for Advanced Studies
- Dionigi Benincasa
October 22, 2012

PIRSA:12100082
Quantum Gravity
The cosmological constant and the emergence of the continuum

Lorenzo Sindoni Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
October 22, 2012

PIRSA:12100081
Cosmology
An analogue model lesson for the cosmological constant

Stefano Liberati SISSA International School for Advanced Studies
October 22, 2012

PIRSA:12100080
Cosmology
Improved test of the Equivalence Principle as a probe of quantum gravity
- James Overduin Towson University
- Daniel Sudarsky Universidad Nacional Autónoma De Mexico (UNAM)
October 22, 2012

PIRSA:12100127
Quantum Gravity
Matter-wave clocks

Holger Mueller University of California, Berkeley
October 22, 2012

PIRSA:12100124
Quantum Gravity
Causal Constraints on Possible Measurements

Leron Borsten Heriot-Watt University
June 28, 2012

PIRSA:12060078
Quantum Fields and Strings
Holographic Mutual Information is Monogamous

Patrick Hayden Stanford University
June 28, 2012

PIRSA:12060070
Quantum Information
Quantum Tasks in Minkowski Space

Adrian Kent University of Cambridge
June 28, 2012

PIRSA:12060062
Mathematical physics
Entanglement Generation in Relativistic Quantum Fields

June 28, 2012

PIRSA:12060068
On the Preparation of States in Nonlinear Quantum Mechanics

Nicolas Menicucci Royal Melbourne Institute of Technology University (RMIT)
June 28, 2012

PIRSA:12060048
Quantum Fields and Strings
Photon Location in Rindler Coordinates

June 28, 2012

PIRSA:12060066
Any Quantum State Can be Cloned in the Presence of a Closed Timelike Curve

June 28, 2012

PIRSA:12060075

Is there a MesoScale in Quantum Gravity? Is it a Non-Locality Scale?
- Laurent Freidel Perimeter Institute for Theoretical Physics
- Stefano Liberati SISSA International School for Advanced Studies
- Dionigi Benincasa
October 22, 2012

PIRSA:12100082
Quantum Gravity
The cosmological constant and the emergence of the continuum

Lorenzo Sindoni Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
October 22, 2012

PIRSA:12100081
Cosmology
Naturalness problems that could be signaling the necessity a completion of an effective field theory with the introduction of an otherwise overlooked ingredient. The cosmological constant problem can be seen as a signal that the EFT for gravity, general relativity, is not correctly including the gravitational properties of the vacuum. Starting from the discussion of the a possible solution to this naturalness problem for a cc-like term in a BEC analogue model, I will briefly discuss how this particular mechanism can be extended, albeit in a preliminary form, to more genuine quantum gravity models like GFT, connecting in particular the problem of the determination of the gravitational couplings (and hence the hierarchies involved) to the appearance of a semiclassical space-time
An analogue model lesson for the cosmological constant

Stefano Liberati SISSA International School for Advanced Studies
October 22, 2012

PIRSA:12100080
Cosmology
Analogue models of gravity have been a test field for many phenomena in quantum field theory on curved spacetimes. It was recently recognized that in some situations they can also provide toy models of emergent gravity. We shall review here such a model and address within it the nature and scale of the cosmological constrant trying to draw general lessons for emergent gravity scenarios.
Improved test of the Equivalence Principle as a probe of quantum gravity
- James Overduin Towson University
- Daniel Sudarsky Universidad Nacional Autónoma De Mexico (UNAM)
October 22, 2012

PIRSA:12100127
Quantum Gravity
Current approaches to the problems of dark energy and unification generically predict the existence of new fields (quintessence dilatons etc.) that will in principle couple with different strengths to different standard-model fields. These different coupling strengths will cause test materials of different compositions to fall at different rates in the same gravitational field violating the Equivalence Principle the foundation of General Relativity. A sufficiently sensitive measurement of the relative accelerations of different test bodies in orbit around the earth could detect or rule out these new fields complementing existing or proposed experiments in high-energy physics (colliders) and observational cosmology (space telescopes). To do this convincingly such an experiment needs at least three test materials spanning the largest possible volume in the space of atomic and molecular properties and a sensitivity to EP violations of as little as a part in $10^{18}$ (attainable only in space and at low temperatures). I discuss one such experiment the Satellite Test of the Equivalence Principle which has reached an advanced stage of prototype development and is currently awaiting a path toward a flight program.
Matter-wave clocks

Holger Mueller University of California, Berkeley
October 22, 2012

PIRSA:12100124
Quantum Gravity
Causal Constraints on Possible Measurements

Leron Borsten Heriot-Watt University
June 28, 2012

PIRSA:12060078
Quantum Fields and Strings
A crucial question in any approach to quantum information processing is: first, how are classical bits encoded physically in the quantum system, second, how are they then manipulated and, third, how are they finally read out? These questions are particularly challenging when investigating quantum information processing in a relativistic spacetime. An obvious framework for such an investigation is relativistic quantum field theory. Here, progress is hampered by the lack of a universally applicable rule for calculating the probabilities of the outcomes of ideal measurements on a relativistic quantum field in a collection of spacetime regions. Indeed, a straightforward relativistic generalisation of the non-relativistic formula for these probabilities leads to superluminal signalling.

Motivated by these considerations we ask what interventions/ideal measurements can we in principle make, taking causality as our guiding criterion. In the course of this analysis we reconsider various aspects of ideal measurements in QFT, detector models and the probability rules themselves. In particular, it is shown that an ideal measurement of a one–particle wave packet state of a relativistic quantum field in Minkowski spacetime enables superluminal signalling. The result holds for a measurement that takes place over an intervention region in spacetime whose extent in time in some frame is longer than the light crossing time of the packet in that frame.
Holographic Mutual Information is Monogamous

Patrick Hayden Stanford University
June 28, 2012

PIRSA:12060070
Quantum Information
I'll describe a special information-theoretic property of quantum field theories with holographic duals: the mutual informations among arbitrary disjoint spatial regions A,B,C obey the inequality I(A:BC) >= I(A:B)+I(A:C), provided entanglement entropies are given by the Ryu-Takayanagi formula. Inequalities of this type are known as monogamy relations and are characteristic of measures of quantum entanglement. This suggests that correlations in holographic theories arise primarily from entanglement rather than classical correlations. Moreover, monogamy property implies that the Ryu-Takayanagi formula is consistent with all known general inequalities obeyed by the entanglement entropy, including an infinite set recently discovered by Cadney, Linden, and Winter; this constitutes significant evidence in favour of its validity.
Quantum Tasks in Minkowski Space

Adrian Kent University of Cambridge
June 28, 2012

PIRSA:12060062
Mathematical physics
The fundamental properties of quantum information and its applications to computing and cryptography have been greatly illuminated by considering information-theoretic tasks that are provably possible or impossible within non-relativistic quantum mechanics. In this talk I describe a general framework for defining tasks within (special) relativistic quantum theory and illustrate it with examples from relativistic quantum cryptography.
Entanglement Generation in Relativistic Quantum Fields

June 28, 2012

PIRSA:12060068

We present a general, analytic recipe to compute the entanglement that is generated between arbitrary, discrete modes of bosonic quantum fields by Bogoliubov transformations. Our setup allows the complete characterization of the quantum correlations in all Gaussian field states. Additionally, it holds for all Bogoliubov transformations. These are commonly applied in quantum optics for the description of squeezing operations, relate the modedecompositions of observers in different regions of curved spacetimes, and describe observers moving along non-stationary trajectories. We focus on a quantum optical example in a cavity quantum electrodynamics setting: an uncharged scalar field within a cavity provides a model for an optical resonator, in which entanglement is created by non-uniform acceleration.We show that the amount of generated entanglement can be magnified by initialsingle-mode squeezing, for which we provide an explicit formula.Applications to quantum fields in curved spacetimes, such as an expanding universe, are discussed.
On the Preparation of States in Nonlinear Quantum Mechanics

Nicolas Menicucci Royal Melbourne Institute of Technology University (RMIT)
June 28, 2012

PIRSA:12060048
Quantum Fields and Strings
Recent analysis of closed timelike curves from an information-theoretic perspective has led to contradictory conclusions about their information-processing power. One thing is generally agreed upon, however, which is that if such curves exist, the quantum-like evolution they imply would be nonlinear, but the physical interpretation of such theories is still unclear. It is known that any operationally verifiable instance of a nonlinear, deterministic evolution on some set of pure states makes the density matrix inadequate for representing mixtures of those pure states. We re-cast the problem in the language of operational quantum mechanics, building on previous work to show that the no-signalling requirement leads to a splitting of the equivalence classes of preparation procedures. This leads to the conclusion that any non-linear theory satisfying certain minimal conditions must be regarded as inconsistent unless it contains distinct representations for the two different kinds of mixtures, and incomplete unless it contains a rule for determining the physical preparations associated with each type. We refer to this as the `preparation problem' for nonlinear theories.
Photon Location in Rindler Coordinates

June 28, 2012

PIRSA:12060066

Bases of orthonormal localized states are constructed in Rindler coordinates and applied to an Unruh detector with good time resolution and an accelerated rod-like array detector.
Any Quantum State Can be Cloned in the Presence of a Closed Timelike Curve

June 28, 2012

PIRSA:12060075

Using the Deutsch approach, we show that the no-cloning theorem can be circumvented in the presence of closed timelike curves, allowing the perfect cloning of a quantum state chosen randomly from a finite alphabet of states. Further, we show that a universal cloner can be constructed that when acting on a completely arbitrary qubit state, exceeds the no-cloning bound on fidelity. Since the “no cloning theorem” has played a central role in the development of quantum information science, it is clear that the existence of closed timelike curves would radically change the rules for quantum information technology.

Title	Speaker(s)	Date	Talk Type	Info link
Is there a MesoScale in Quantum Gravity? Is it a Non-Locality Scale?	Laurent Freidel, Stefano Liberati, Dionigi Benincasa	2012-10-22	Conference	View details
The cosmological constant and the emergence of the continuum	Lorenzo Sindoni	2012-10-22	Conference	View details
An analogue model lesson for the cosmological constant	Stefano Liberati	2012-10-22	Conference	View details
Improved test of the Equivalence Principle as a probe of quantum gravity	James Overduin, Daniel Sudarsky	2012-10-22	Conference	View details
Matter-wave clocks	Holger Mueller	2012-10-22	Conference	View details
Causal Constraints on Possible Measurements	Leron Borsten	2012-06-28	Conference	View details
Holographic Mutual Information is Monogamous	Patrick Hayden	2012-06-28	Conference	View details
Quantum Tasks in Minkowski Space	Adrian Kent	2012-06-28	Conference	View details
Entanglement Generation in Relativistic Quantum Fields		2012-06-28	Conference	View details
On the Preparation of States in Nonlinear Quantum Mechanics	Nicolas Menicucci	2012-06-28	Conference	View details
Photon Location in Rindler Coordinates		2012-06-28	Conference	View details
Any Quantum State Can be Cloned in the Presence of a Closed Timelike Curve		2012-06-28	Conference	View details

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