13309 - 13320 of 20115 Results
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Smash, Bang, Boom: Fundamental Physics at the LHC
Natalia Toro Stanford University
The Path Integral Interpretation of Quantum Mechanics
Fay Dowker Imperial College London
PIRSA:12070001Causal Constraints on Possible Measurements
Leron Borsten Heriot-Watt University
Holographic Mutual Information is Monogamous
Patrick Hayden Stanford University
Quantum Tasks in Minkowski Space
Adrian Kent University of Cambridge
Entanglement Generation in Relativistic Quantum Fields
PIRSA:12060068On the Preparation of States in Nonlinear Quantum Mechanics
Nicolas Menicucci Royal Melbourne Institute of Technology University (RMIT)
Photon Location in Rindler Coordinates
PIRSA:12060066
Entangling Superconductivity and antiferromagnetism: Quantum Monte Carlo without the sign Problem
Subir Sachdev Harvard University
It has long been known that a metal near an instability to antiferromagnetism also has a weak-coupling Cooper instability to spin-singlet d-wave-like superconductivity. However, the theory of the antiferromagnetic quantum critical point flows to strong-coupling in two spatial dimensions, and so the fate of the superconductivity has also been unclear. I will describe a method to realize the generic antiferromagnetic quantum critical in a metal in a sign-problem-free Monte Carlo simulation. Results showing Fermi surface reconstruction and unconventional spin-singlet superconductivity across the critical point are obtained.Smash, Bang, Boom: Fundamental Physics at the LHC
Natalia Toro Stanford University
The world's most ambitious scientific experiment is buried 100 meters underground, straddling Switzerland and France. A billion times every minute, the Large Hadron Collider (LHC) slams together protons, while four giant detectors watch closely. - So how does the Large Hadron Collider work? - Why can slamming tiny particles into each other provide clues about the nature of all space and time? - What mysteries are physicists trying to solve with data from the LHC? - How does the cutting edge of particle physics relate to the world around us, from the patterns of stars in the sky to the fact that they shine at all? Natalia Toro, PI Faculty, works at the intersection of theories and hard data. She will explain how complex collision data from the LHC is being digested and examined right now, and how it may set the course for the science of the future.The Path Integral Interpretation of Quantum Mechanics
Fay Dowker Imperial College London
PIRSA:12070001Modern Cosmology
Niayesh Afshordi University of Waterloo
This presentation will cover a number of topics in cosmology today including dark energy, dark matter and the cosmological constant.Causal Constraints on Possible Measurements
Leron Borsten Heriot-Watt University
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
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
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
PIRSA:12060068We 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)
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
PIRSA:12060066Bases 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
PIRSA:12060075Using 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.