Relativistic Quantum Information - 2012

36 talks

June 25, 2012 - June 28, 2012

C12030

Collection Type

Conference/School

Description

Relativistic Quantum Information

Displaying 1 - 12 of 36

The Quest for Localization

Juan José León García
Instituto de Física Fundamental (IFF - CSIC)

June 25, 2012

PIRSA:12060044
Entanglement of a Relativistic Field in the Vacuum State

Benni Reznik
Tel Aviv University
June 25, 2012

PIRSA:12060069
Quantum Fields and Strings
Physical Results with Fermions in RQI

June 25, 2012

PIRSA:12060046
Quantum Teleportation from Alice to Rob in Vacuum

Shih-Yuin Lin
National Changhua University of Education

June 25, 2012

PIRSA:12060047
Geometric Discord in Non-Inertial Frames

Eric Brown
University of Chicago

June 25, 2012

PIRSA:12060058
Tripartite Entanglement, Svetlichny Inequalities, and Non-inertial Observers

Robert Mann
University of Waterloo

June 25, 2012

PIRSA:12060042
Boundary Effects on Quantum Entanglement and its Dynamics in a Detector-Field System

June 25, 2012

PIRSA:12060074
Towards Universal Quantum Computation Out of Relativistic Motion of Particle Detectors

David Aasen
California Institute of Technology

June 25, 2012

PIRSA:12060049
Nonlocality, Entanglement Witnesses and Supra-Correlations

Paul Alsing
United States Air Force Research Laboratory

June 25, 2012

PIRSA:12060076
Quantum Interference of “Clocks”

Časlav Brukner
Institute for Quantum Optics and Quantum Information (IQOQI) - Vienna

June 26, 2012

PIRSA:12060050
Localised Detection of Relativistic Quantum Fields in Non-Inertial Frames

Andrzej Dragan
University of Warsaw

June 26, 2012

PIRSA:12060040
Localised Detection of the Unruh Effect

June 26, 2012

PIRSA:12060052

The Quest for Localization

Juan José León García
Instituto de Física Fundamental (IFF - CSIC)

June 25, 2012

PIRSA:12060044

This talk aims to review the obstacles met in QFT to reach an appropriate definition for such a basic concept as localization. The anti-local character of the square root of the "- Laplace-Beltrami + mass^2" operator prevents the existence of localized states with a finite number of quanta. (Bosonic) quantum fields describe elementary excitations of an extended system whose ground state is the vacuum. No wonder, there is a complicated relationship between the cardinal (quantal) and continuous (spatial) sides of the theory. We will also analyze the roles (if any) played in RQI by the localized excitations of the vacuum.
Entanglement of a Relativistic Field in the Vacuum State

Benni Reznik
Tel Aviv University
June 25, 2012

PIRSA:12060069
Quantum Fields and Strings
We discuss gedanken experiments for measuring local and non-local observables in QFT that
respect causality, and can by used to test the entanglement between two spatially distant regions in the vacuum. It is shown that the entanglement decays exponentially with the distance between the regions and does not vanish, in contrast to the case of lattice models. We discuss in this respect a possible mechanism which might explain this persistence effect, and a connection between the Reeh-Schlieder theorem and superoscillations.
Physical Results with Fermions in RQI

June 25, 2012

PIRSA:12060046

A number of works in the field of relativistic quantum information have been devoted to the study of entanglement on certain simple families of Unruh-mode entangled states in non-inertial frames. In the fermionic case remarkable results such as the survival of entanglement at infinite acceleration have been obtained. In this talk we will present and analyze some issues related to the anticommuting character of fermionic field operators, which have been overlooked in the past, sometimes leading to unphysical results. We provide a simple way of obtaining physical results, yielding interesting consequences such as convergence of field entanglement for different families of Unruh mode-entangled states in the infinite acceleration limit.
Quantum Teleportation from Alice to Rob in Vacuum

Shih-Yuin Lin
National Changhua University of Education

June 25, 2012

PIRSA:12060047

We consider quantum teleportation of continuous variables in a relativistic system with the Unruh-DeWitt detectorscoupled to a common quantum field initially in the Minkowski vacuum. An unknown coherent state of an Unruh-DeWitt detector is teleported from one inertial agent (Alice) to an almost uniformly accelerated agent (Rob), using a detector pair initially entangled and shared by these two agents. Results for the averaged physical fidelity of quantum teleportation will be discussed.
Geometric Discord in Non-Inertial Frames

Eric Brown
University of Chicago

June 25, 2012

PIRSA:12060058

I review the recent work performed on computing the geometric discord in non-inertial frames. We consider the well-known case of an inertially maximally entangled state shared by inertial Alice and non-inertial Robb. It is found that for high accelerations the geometric discord decays to a negligible amount; this is in stark contrast to the entropic definition of quantum discord which asymptotes to a finite value in the same limit. Such a result has two different implications: the first being that usable quantum correlations are more limited in this regime than previously thought and the second being that geometric discord may not be a sufficient measure of quantum correlations. I will discuss both of these perspectives.
Tripartite Entanglement, Svetlichny Inequalities, and Non-inertial Observers

Robert Mann
University of Waterloo

June 25, 2012

PIRSA:12060042

I discuss the behaviour of bipartite and tripartite non-locality between fermionic entangled states shared by observers, one of whom uniformly accelerates. Although fermionic entanglement persists for arbitrarily large acceleration, the Bell/CHSH inequalities cannot be violated for sufficiently large but finite acceleration. However the Svetlichny inequality, which is a measure of genuine tripartite non-locality, can be violated for any finite value of the acceleration.
Boundary Effects on Quantum Entanglement and its Dynamics in a Detector-Field System

June 25, 2012

PIRSA:12060074

We analyze an exactly solvable model consisting of an inertial Unruh-DeWitt detector which interacts linearly with a massless quantum field in Minkowski spacetime with a perfectly reflecting flat plane boundary. This model is related to proposed mirror-field superposition and relevant experiments in macroscopic quantum phenomena, as well as atomic fluctuation forces near a conducting surface. Firstly a coupled set of equations for the detector’s and the field’s Heisenberg operators are derived. After coarse graining the field, the dynamics of the detector’s internal degreeof freedom is described by a quantum Langevin equation, where the dissipation and noise kernels respectively correspond to the retarded Green’s functions and Hadamard elementary functions of the free quantum field in half space. We use the linear entropy as measures of entanglement between the detector and the quantum field under mirror reflection, then solve the early-time detector-fieldentanglement dynamics. At late times when the combined system is in a stationary state, we obtain exact expressions for the detector’s covariance matrix and show that the detector-field entanglement decreases for smaller separation between the detector and the mirror.We explain the behavior of detector-field entanglement qualitatively with the help of a detector’s mirror image, compare them with the case of two real detectors and explain the differences.
Towards Universal Quantum Computation Out of Relativistic Motion of Particle Detectors

David Aasen
California Institute of Technology

June 25, 2012

PIRSA:12060049
Nonlocality, Entanglement Witnesses and Supra-Correlations

Paul Alsing
United States Air Force Research Laboratory

June 25, 2012

PIRSA:12060076

While entanglement is believed to underlie the power of quantum computation and communication, it is not generally well understood for multipartite systems. Recently, it has been appreciated that there exists proper no-signaling probability distributions derivable from operators that do not represent valid quantum states. Such systems exhibit supra-correlations that are stronger than allowed by quantum mechanics, but less than the algebraically allowed maximum in Bell-inequalities (in the bipartite case). Some of these probability distributions are derivable from an entanglement witness W, which is a non-positive Hermitian operator constructed such that its expectation value with a separable quantum state (positive density matrix) rho_sep is non-negative (so that Tr[W rho]< 0 indicates entanglement in quantum state rho). In the bipartite case, it is known that by a modification of the local no-signaling measurements by spacelike separated parties A and B, the supra-correlations exhibited by any W can be modeled as derivable from a physically realizable quantum state ρ. However, this result does not generalize to the n-partite case for n>2. Supra-correlations can also be exhibited in 2- and 3-qubit systems by explicitly constructing "states" O (not necessarily positive quantum states) that exhibit PR correlations for a fixed, but arbitrary number, of measurements available to each party. In this paper we examine the structure of "states" that exhibit supra-correlations. In addition, we examine the affect upon the distribution of the correlations amongst the parties involved when constraints of positivity and purity are imposed. We investigate circumstances in which such "states" do and do not represent valid quantum states.
Quantum Interference of “Clocks”

Časlav Brukner
Institute for Quantum Optics and Quantum Information (IQOQI) - Vienna

June 26, 2012

PIRSA:12060050

Experimental tests of general relativity performed so far involve systems that can be effectively described by classical physics. On the other hand, observed gravity effects on quantum systems do not go beyond the Newtonian limit of the theory. In light of the conceptual differences between general relativity and quantum mechanics, as well as those of finding a unified theoretical framework for the two theories, it is of particular interest to look for feasible experiments that can only be explained if both theories apply. We propose testing general relativistic time dilation with a single “clock” in a superposition of two paths in space-time, along which time flows at different rates. We show that the interference visibility in such an experiment will decrease to the extent to which the path information becomes available from reading out the time from the “clock”. This effect would provide the first test of the genuine general relativistic notion of time in quantum mechanics. We consider implementation of the “clock” in evolving internal degrees of freedom of a massive particle and, alternatively, in the external degree of a photon and analyze the feasibility of the experiment.
Localised Detection of Relativistic Quantum Fields in Non-Inertial Frames

Andrzej Dragan
University of Warsaw

June 26, 2012

PIRSA:12060040

We introduce a novel approach to measurements in QFT in non-inertial frames. A simple, localised, analytical model of state detection allows us to study all the standard questions of RQI and yielding simple answers with a clear physical interpretation. We apply the model to investigate extraction of the entanglement from the vacuum, completely characterize entangled state of two localised inertial wave-packets in the accelerating frame and study the entanglement degradation as a function of the proper acceleration of the detector.
Localised Detection of the Unruh Effect

June 26, 2012

PIRSA:12060052

I will discuss a new proposal with the potential to experimentally probe the validity of Rindler quantisation from the recent completely localized framework of non-inertial projective detectors of quantum fields.

Title	Speaker(s)	Date	Talk Type	Info
The Quest for Localization	Juan José León García	2012-06-25	Conference	View details
Entanglement of a Relativistic Field in the Vacuum State	Benni Reznik	2012-06-25	Conference	View details
Physical Results with Fermions in RQI		2012-06-25	Conference	View details
Quantum Teleportation from Alice to Rob in Vacuum	Shih-Yuin Lin	2012-06-25	Conference	View details
Geometric Discord in Non-Inertial Frames	Eric Brown	2012-06-25	Conference	View details
Tripartite Entanglement, Svetlichny Inequalities, and Non-inertial Observers	Robert Mann	2012-06-25	Conference	View details
Boundary Effects on Quantum Entanglement and its Dynamics in a Detector-Field System		2012-06-25	Conference	View details
Towards Universal Quantum Computation Out of Relativistic Motion of Particle Detectors	David Aasen	2012-06-25	Conference	View details
Nonlocality, Entanglement Witnesses and Supra-Correlations	Paul Alsing	2012-06-25	Conference	View details
Quantum Interference of “Clocks”	Časlav Brukner	2012-06-26	Conference	View details
Localised Detection of Relativistic Quantum Fields in Non-Inertial Frames	Andrzej Dragan	2012-06-26	Conference	View details
Localised Detection of the Unruh Effect		2012-06-26	Conference	View details

Relativistic Quantum Information - 2012

Format results