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Seeing is Believing: Direct Observation of a General Quantum State

Jeff Lundeen University of Ottawa
March 17, 2014

PIRSA:14030110
Quantum Foundations
13/14 PSI - Explorations in String Theory - Lecture 1

Andrei Starinets University of Oxford

March 17, 2014

PIRSA:14030059
13/14 PSI - Explorations in Condensed Matter - Lecture 1

Guifre Vidal Alphabet (United States)

March 17, 2014

PIRSA:14040022
13/14 PSI - Explorations in Quantum Information - Lecture 1

David Cory Institute for Quantum Computing (IQC)

March 17, 2014

PIRSA:14030029
Introduction to Effective Field Theories - Lecture 18

Cliff Burgess McMaster University

March 14, 2014

PIRSA:14030079
Are superselection rules fundamental?

Robert Spekkens Perimeter Institute for Theoretical Physics
March 14, 2014

PIRSA:14030114
Condensed Matter
Introduction to Effective Field Theories - Lecture 17

Cliff Burgess McMaster University

March 14, 2014

PIRSA:14030075
Introduction to Quantum Field Theory for Cosmology - Lecture 18

Achim Kempf University of Waterloo

March 13, 2014

PIRSA:14030004
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

Andrew Strominger Harvard University
March 13, 2014

PIRSA:14030087
Strong Gravity
Maximal Privacy Without Coherence

Debbie Leung Institute for Quantum Computing (IQC)
March 12, 2014

PIRSA:14030105
Quantum Information
Black Holes- the Harmonic Oscillators of the 21st Century

Andrew Strominger Harvard University
March 12, 2014

PIRSA:14030104
Quantum Fields and Strings
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases

Julian (Jose) Rincon Universidad de los Andes
March 12, 2014

PIRSA:14030117
Condensed Matter

Seeing is Believing: Direct Observation of a General Quantum State

Jeff Lundeen University of Ottawa
March 17, 2014

PIRSA:14030110
Quantum Foundations
Central to quantum theory, the wavefunction is a complex distribution associated with a quantum system. Despite its fundamental role, it is typically introduced as an abstract element of the theory with no explicit definition. Rather, physicists come to a working understanding of it through its use to calculate measurement outcome probabilities through the Born Rule. Tomographic methods can reconstruct the wavefunction from measured probabilities. In contrast, I present a method to directly measure the wavefunction so that its real and imaginary components appear straight on our measurement apparatus. I will also present new work extending this concept to mixed quantum states. This extension directly measures a little-known proposal by Dirac for a classical analog to a quantum operator. Furthermore, it reveals that our direct measurement is a rigorous example of a quasi-probability phase-space (i.e. x,p) distribution that is closely related to the Q, P, and Wigner functions. Our direct measurement method gives the quantum state a plain and general meaning in terms of a specific set of simple operations in the lab.
13/14 PSI - Explorations in String Theory - Lecture 1

Andrei Starinets University of Oxford

March 17, 2014

PIRSA:14030059
13/14 PSI - Explorations in Condensed Matter - Lecture 1

Guifre Vidal Alphabet (United States)

March 17, 2014

PIRSA:14040022
13/14 PSI - Explorations in Quantum Information - Lecture 1

David Cory Institute for Quantum Computing (IQC)

March 17, 2014

PIRSA:14030029
Introduction to Effective Field Theories - Lecture 18

Cliff Burgess McMaster University

March 14, 2014

PIRSA:14030079
Are superselection rules fundamental?

Robert Spekkens Perimeter Institute for Theoretical Physics
March 14, 2014

PIRSA:14030114
Condensed Matter
Superselection rules in quantum theory assert the impossibility of preparing coherent superpositions of certain conserved quantities. For instance, it is commonly presumed that there is a superselection rule for charge and for baryon number, as well as a "univalence superselection rule" forbidding a coherent superposition of a fermion and a boson. I will show how many superselection rules can be effectively lifted using a reference frame for the variable that is conjugate to the conserved quantity. I will also discuss subtleties related to the univalence superselection rule.
Introduction to Effective Field Theories - Lecture 17

Cliff Burgess McMaster University

March 14, 2014

PIRSA:14030075
Introduction to Quantum Field Theory for Cosmology - Lecture 18

Achim Kempf University of Waterloo

March 13, 2014

PIRSA:14030004
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space

Andrew Strominger Harvard University
March 13, 2014

PIRSA:14030087
Strong Gravity
We argue that the infinite-dimensional BMS symmetry discovered by Bondi et. al in the 60s provides an exact symmetry of the quantum gravity S-matrix. The Ward identity of this symmetry is shown to be precisely Weinberg's soft graviton theorem, also discovered in the 60s. A parallel infinite-dimensional symmetry is found to be generated in nonabelian gauge theories by gauge transformations which go to an angle-dependent finite constant at null infinity. The Ward identity of this symmetry is shown to be the soft gluon theorem.
Maximal Privacy Without Coherence

Debbie Leung Institute for Quantum Computing (IQC)
March 12, 2014

PIRSA:14030105
Quantum Information
Privacy and coherence have long been considered closely related properties of a quantum state. Indeed, a coherently transmitted quantum state is inherently private. Surprisingly, coherent quantum communication is not always required for privacy: there are quantum channels that are too noisy to transmit quantum information but it can send private classical information. Here, we ask how different the private classical and the quantum capacities can be. We present a class of channels N_d with input dimension d^2, quantum capacity Q(N_d) <= 1, and private classical capacity P(N_d) = log d. These channels asymptotically saturate an interesting inequality P(N) <= (log d_A + Q(N))/2 for any channel N with input dimension d_A, and capture the essence of privacy stripped of the confounding influence of coherence.
Black Holes- the Harmonic Oscillators of the 21st Century

Andrew Strominger Harvard University
March 12, 2014

PIRSA:14030104
Quantum Fields and Strings
In the twentieth century, many problems across all of physics were solved by perturbative methods which reduced them to harmonic oscillators. Black holes are poised to play a similar role for the problems of twenty-first century physics. They are at once the simplest and most complex objects in the physical universe. They are maximally complex in that the number of possible microstates, or entropy, of a black hole is believed to saturate a universal bound. They are maximally simple in that, according to Einstein's theory, they are featureless holes in space characterized only by their mass, charge and angular momentum. This dual relation between simplicity and complexity, as expressed in black holes, has recently been successfully applied to problems in a disparate variety of physical systems. I will give an introduction to the subject intended for a general audience.
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases

Julian (Jose) Rincon Universidad de los Andes
March 12, 2014

PIRSA:14030117
Condensed Matter

Title	Date	Collection	Type	Info
Seeing is Believing: Direct Observation of a General Quantum State	2014‑03‑17	Quantum Foundations	Scientific Series	View details
13/14 PSI - Explorations in String Theory - Lecture 1	2014‑03‑17	13/14 PSI - Explorations in String Theory	Course	View details
13/14 PSI - Explorations in Condensed Matter - Lecture 1	2014‑03‑17	13/14 PSI - Explorations in Condensed Matter	Course	View details
13/14 PSI - Explorations in Quantum Information - Lecture 1	2014‑03‑17	13/14 PSI - Explorations in Quantum Information	Course	View details
Introduction to Effective Field Theories - Lecture 18	2014‑03‑14	Introduction to Effective Field Theories	Course	View details
Are superselection rules fundamental?	2014‑03‑14	Quantum Matter	Scientific Series	View details
Introduction to Effective Field Theories - Lecture 17	2014‑03‑14	Introduction to Effective Field Theories	Course	View details
Introduction to Quantum Field Theory for Cosmology - Lecture 18	2014‑03‑13	Quantum Field Theory for Cosmology - 2014	Course	View details
Asymptotic Symmetries of Gauge and Gravity Theories in Minkowski Space	2014‑03‑13	Strong Gravity	Scientific Series	View details
Maximal Privacy Without Coherence	2014‑03‑12	Perimeter Institute Quantum Discussions	Scientific Series	View details
Black Holes- the Harmonic Oscillators of the 21st Century	2014‑03‑12	Colloquium	Scientific Series	View details
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases	2014‑03‑12	Quantum Matter	Scientific Series	View details

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