Quantum Physics

Displaying 1489 - 1500 of 2289

Time, cosmology and quantum foundations

Lee Smolin Perimeter Institute for Theoretical Physics
May 31, 2013

PIRSA:13050072
Quantum Physics

Astrophysics
Generalizations of Quantum Theory
- Lucien Hardy Perimeter Institute for Theoretical Physics
- Rafael Sorkin Perimeter Institute for Theoretical Physics
- Wayne Myrvold Western University
- Howard Barnum University of New Mexico
- Joe Henson BNP Paribas Asset Management London
- Markus Müller Austrian Academy of Sciences
May 30, 2013

PIRSA:13050081
Quantum Physics

High Energy Physics
Path Integrals, Reality and Generalizations of Quantum Theory

Adrian Kent University of Cambridge
May 29, 2013

PIRSA:13050065
Quantum Physics

Quantum Physics
Constraints on generalizations of quantum theory
- Adan Cabello Universidad de Sevilla
- Robert Spekkens Perimeter Institute for Theoretical Physics
- Joseph Emerson Institute for Quantum Computing (IQC)
- Terry Rudolph Imperial College London
- Renato Renner ETH Zurich
May 28, 2013

PIRSA:13050085
Quantum Physics

High Energy Physics
The Quantum-Mechanical Measurement Problem and the Foundations of Statistical Mechanics

David Albert Columbia University
May 28, 2013

PIRSA:13050062
Quantum Physics
Information Theoretic Benefit of Entanglement in Classical Communication Settings

Salman Beigi Institute for Research in Fundamental Sciences (IPM)
May 27, 2013

PIRSA:13050077
Quantum Physics
On the non-extendibility of quantum theory
May 27, 2013

PIRSA:13050059
Quantum Physics
Completing Canonical Quantization

John Klauder University of Florida
May 21, 2013

PIRSA:13050006
Quantum Physics
Processing quantum information with relativistic motion of atoms

Eduardo Martin-Martinez University of Waterloo
May 13, 2013

PIRSA:13050017
Quantum Physics
Entanglement at strongly-interacting quantum critical points in 2+1D

Roger Melko University of Waterloo
May 10, 2013

PIRSA:13050051
Quantum Physics
Twisted Symmetry in Tensor Network States and Topological Order

Oliver Buerschaper Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Physics

Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Physics

Condensed Matter

Time, cosmology and quantum foundations

Lee Smolin Perimeter Institute for Theoretical Physics
May 31, 2013

PIRSA:13050072
Quantum Physics

Astrophysics
I argue that quantum mechanics cannot usefully be extended to a theory of the whole universe, so the task of quantum foundations is to discover that cosmological theory which reduces to quantum mechanics when restricted to small subsystems of the universe. I argue that that cosmological theory will be based on a global notion of physical time which implies the distinction between past, present and future is real and objective. These motivate two examples of novel formulations of quantum theory: the real ensemble formulation and the principle of precedence. Each may imply departures from the expected quantum evolution for sufficiently large and complex quantum systems.
Generalizations of Quantum Theory
- Lucien Hardy Perimeter Institute for Theoretical Physics
- Rafael Sorkin Perimeter Institute for Theoretical Physics
- Wayne Myrvold Western University
- Howard Barnum University of New Mexico
- Joe Henson BNP Paribas Asset Management London
- Markus Müller Austrian Academy of Sciences
May 30, 2013

PIRSA:13050081
Quantum Physics

High Energy Physics
Path Integrals, Reality and Generalizations of Quantum Theory

Adrian Kent University of Cambridge
May 29, 2013

PIRSA:13050065
Quantum Physics

Quantum Physics
I describe some tentative new ideas on modified versions of quantum theory motivated by the path integral formalism, and on other generalizations, and comment on possible experimental implications.
Constraints on generalizations of quantum theory
- Adan Cabello Universidad de Sevilla
- Robert Spekkens Perimeter Institute for Theoretical Physics
- Joseph Emerson Institute for Quantum Computing (IQC)
- Terry Rudolph Imperial College London
- Renato Renner ETH Zurich
May 28, 2013

PIRSA:13050085
Quantum Physics

High Energy Physics
The Quantum-Mechanical Measurement Problem and the Foundations of Statistical Mechanics

David Albert Columbia University
May 28, 2013

PIRSA:13050062
Quantum Physics
Information Theoretic Benefit of Entanglement in Classical Communication Settings

Salman Beigi Institute for Research in Fundamental Sciences (IPM)
May 27, 2013

PIRSA:13050077
Quantum Physics
Expressions of several information theoretic quantities involve an optimization over auxiliary quantum registers. Entanglement-assisted version of some classical communication problems provides examples of such expressions. Evaluating these expressions requires bounds on the dimension of these auxiliary registers. In the classical case such a bound can usually be obtained based on the
Caratheodory theorem, but we know almost no method to bound the dimension of auxiliary quantum registers. In this talk to compare the classical and quantum sides of the problem the notion of “quantum convexification” will be defined. It will be shown that quantum convexification is strictly richer that the usual classical convexification. Moreover some techniques will be discussed which might be useful for bounding the dimension of quantum auxiliary registers.
On the non-extendibility of quantum theory
May 27, 2013

PIRSA:13050059
Quantum Physics
I will present a recent theorem that asserts that there cannot exist an "extension of quantum theory" that allows us to make more informative predictions about future measurable events (e.g., whether a horizontally polarized photon passes a polarization filter with a given orientation) than standard quantum theory. The theorem is based on two assumptions about the extended theory: (i) the theory should be compatible with quantum theory (this means, in practice, that the theory is not falsified by current experimental data); (ii) the theory should not preclude experimenters from freely choosing the measurement settings. More precisely, the latter assumption corresponds to the requirement that measurement settings can be chosen at random such that they are independent of any other events, except of course those that lie in the causal future of the choice (i.e., in its future light cone). In addition, I will discuss a corollary of the non-extendibility theorem which leads to the same conclusions as a recent theorem by Pusey, Barrett, and Rudolph on the "reality of the quantum state", based only on the above assumptions.
Completing Canonical Quantization

John Klauder University of Florida
May 21, 2013

PIRSA:13050006
Quantum Physics
The process of canonical quantization:is reexamined with the goal of ensuring there is only one reality, where $\hbar>0$, in which classical and quantum theories coexist. Two results are a clarification of the effect of canonical coordinate transformations and the role of Cartesian coordinates. Other results provide validation of alternative quantum procedures that allow acceptable solutions for models that exhibit unacceptable solutions using traditional procedures. Several examples will illustrate advantages of the new classical/quantum connection including one case where conventional methods lead to quantum triviality while the enhanced procedures lead to an acceptable nonlinear quantum behaviour. This seminar uses only simple physical and mathematical concepts, and should be widely accessible.
Processing quantum information with relativistic motion of atoms

Eduardo Martin-Martinez University of Waterloo
May 13, 2013

PIRSA:13050017
Quantum Physics
We show that particle detectors, such as 2-level atoms, in non-inertial motion (or in gravitational fields) could be used to build quantum gates for the processing of quantum information. Concretely, we show that through suitably chosen non-inertial trajectories of the detectors the interaction Hamiltonian's time dependence can be modulated to yield arbitrary rotations in the Bloch sphere due to relativistic quantum effects. Ref. Phys. Rev. Lett. 110, 160501 (2013)
Entanglement at strongly-interacting quantum critical points in 2+1D

Roger Melko University of Waterloo
May 10, 2013

PIRSA:13050051
Quantum Physics
In two or more spatial dimensions, leading-order contributions to the scaling of entanglement entropy typically follow the "area" or boundary law. Although this leading-order scaling is non-universal, at a quantum critical point (QCP), the sub-leading behavior does contain universal physics. Different universal functions can be access through entangling regions of different geometries. For example, for polygonal shaped regions, quantum field theories have demonstrated that the subleading scaling is logarithmic, with a universal coefficient dependent on the number of vertices in the polygon. Although such universal quantities are routinely studied in non-interacting field theories, it often requires numerical simulation to access them in interacting theories. In this talk, I discuss quantum Monte Carlo (QMC) and numerical Linked-Cluster Expansion (NLCE) calculations of the Renyi entropies at the transverse-field Ising model QCP on the 2D square lattice. We calculate the universal coefficient of the vertex-induced logarithmic scaling term, and compare to non-interacting field theory calculations by Casini and Huerta. Also, we examine the shape dependence of the Renyi entropy for finite-size toroidal lattices with smooth boundaries. Such geometries provide a sensitive probe of the gapless wave function in the thermodynamic limit, and give new universal quantities that could be examined by future field-theoretical studies in 2+1D.
Twisted Symmetry in Tensor Network States and Topological Order

Oliver Buerschaper Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Physics

Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Physics

Condensed Matter
The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in certain transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-N\'eel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a possible starting point to understand the recently discovered spin-orbital liquid behavior of Ba_3CuSb_2O_9. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms.

Title	Speaker(s)	Date	Talk Type	Info link
Time, cosmology and quantum foundations	Lee Smolin	2013-05-31	Conference	View details
Generalizations of Quantum Theory	Lucien Hardy, Rafael Sorkin, Wayne Myrvold, Howard Barnum, Joe Henson, Markus Müller	2013-05-30	Conference	View details
Path Integrals, Reality and Generalizations of Quantum Theory	Adrian Kent	2013-05-29	Conference	View details
Constraints on generalizations of quantum theory	Adan Cabello, Robert Spekkens, Joseph Emerson, Terry Rudolph, Renato Renner	2013-05-28	Conference	View details
The Quantum-Mechanical Measurement Problem and the Foundations of Statistical Mechanics	David Albert	2013-05-28	Conference	View details
Information Theoretic Benefit of Entanglement in Classical Communication Settings	Salman Beigi	2013-05-27	Scientific Series	View details
On the non-extendibility of quantum theory		2013-05-27	Conference	View details
Completing Canonical Quantization	John Klauder	2013-05-21	Scientific Series	View details
Processing quantum information with relativistic motion of atoms	Eduardo Martin-Martinez	2013-05-13	Scientific Series	View details
Entanglement at strongly-interacting quantum critical points in 2+1D	Roger Melko	2013-05-10	Conference	View details
Twisted Symmetry in Tensor Network States and Topological Order	Oliver Buerschaper	2013-05-10	Conference	View details
Spin-orbital quantum liquid on the honeycomb lattice	Philippe Corboz	2013-05-09	Conference	View details

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Format results

Time, cosmology and quantum foundations

Generalizations of Quantum Theory

Path Integrals, Reality and Generalizations of Quantum Theory

Constraints on generalizations of quantum theory

The Quantum-Mechanical Measurement Problem and the Foundations of Statistical Mechanics

Information Theoretic Benefit of Entanglement in Classical Communication Settings

On the non-extendibility of quantum theory

Completing Canonical Quantization

Processing quantum information with relativistic motion of atoms

Entanglement at strongly-interacting quantum critical points in 2+1D

Twisted Symmetry in Tensor Network States and Topological Order

Spin-orbital quantum liquid on the honeycomb lattice

Time, cosmology and quantum foundations

Generalizations of Quantum Theory

Path Integrals, Reality and Generalizations of Quantum Theory

Constraints on generalizations of quantum theory

The Quantum-Mechanical Measurement Problem and the Foundations of Statistical Mechanics

Information Theoretic Benefit of Entanglement in Classical Communication Settings

On the non-extendibility of quantum theory

Completing Canonical Quantization

Processing quantum information with relativistic motion of atoms

Entanglement at strongly-interacting quantum critical points in 2+1D

Twisted Symmetry in Tensor Network States and Topological Order

Spin-orbital quantum liquid on the honeycomb lattice