Quantum Information

Quantum mechanics redefines information and its fundamental properties. Researchers at Perimeter Institute work to understand the properties of quantum information and study which information processing tasks are feasible, and which are infeasible or impossible. This includes research in quantum cryptography, which studies the trade-off between information extraction and disturbance, and its applications. It also includes research in quantum error correction, which involves the study of methods for protecting information against decoherence. Another important side of the field is studying the application of quantum information techniques and insights to other areas of physics, including quantum foundations and condensed matter.

Displaying 877 - 888 of 1338

Generalized Relative Entropies, Entanglement Monotones and One-Shot Information Theory

Nilanjana Datta
University of Cambridge
June 17, 2013

PIRSA:13060003
Quantum Information
Quantum Factoring with Trapped Ions - A test of scalability

Isaac Chuang
Massachusetts Institute of Technology (MIT)
June 12, 2013

PIRSA:13060002
Quantum Information
Quantum Measurement in the Real World

Aephraim Steinberg
University of Toronto
June 05, 2013

PIRSA:13060001
Quantum Information
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
  Institute for Quantum Optics and Quantum Information (IQOQI) - Vienna
May 30, 2013

PIRSA:13050081
Quantum Information

Quantum Fields and Strings
Path Integrals, Reality and Generalizations of Quantum Theory

Adrian Kent
University of Cambridge
May 29, 2013

PIRSA:13050065
Quantum Information

Quantum Foundations
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 Information

Quantum Fields and Strings
Information Theoretic Benefit of Entanglement in Classical Communication Settings

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

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

PIRSA:13050059
Quantum Information
Processing quantum information with relativistic motion of atoms

Eduardo Martin-Martinez
University of Waterloo
May 13, 2013

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

Roger Melko
University of Waterloo
May 10, 2013

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

Oliver Buerschaper
Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Information

Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz
Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Information

Condensed Matter

Generalized Relative Entropies, Entanglement Monotones and One-Shot Information Theory

Nilanjana Datta
University of Cambridge
June 17, 2013

PIRSA:13060003
Quantum Information
We introduce two relative entropy quantities called the min- and max-relative
entropies and discuss their properties and operational meanings.

These relative entropies act as parent quantities for tasks such as data compression, information
transmission and entanglement manipulation in one-shot information theory. Moreover, they lead us to define entanglement monotones which have interesting operational interpretations.
Quantum Factoring with Trapped Ions - A test of scalability

Isaac Chuang
Massachusetts Institute of Technology (MIT)
June 12, 2013

PIRSA:13060002
Quantum Information
Shor's algorithm can be a meaningful test for experimental quantum processing systems, when suitably realized. I present results from a recent implemenation of quantum factoring using trapped ion qubits, demonstrating feed-forward control, use of quantum memory during computation, and cascaded three-qubit gates. Such capabilities are necessary ingredients for a future large-scale,
fault-tolerant quantum computing system.
Quantum Measurement in the Real World

Aephraim Steinberg
University of Toronto
June 05, 2013

PIRSA:13060001
Quantum Information
While quantum measurement remains the central philosophical conundrum of quantum mechanics, it has recently grown into a respectable (read: experimental!) discipline as well. New perspectives on measurement have grown out of new technological possibilities, but also out of
attempts to design systems for quantum information processing, which promise to be exponentially more powerful than any possible classical computer. I will try to give a flavour about some of these perspectives, focussing largely on a particular paradigm known as "weak measurement."
Weak measurement is a natural extension of a pragmatic view of what it means to measure something about a quantum system, yet leads to some rather surprising results. I will describe a few examples of our recent experiments using weak measurement to probe fundamental issues in uantum mechanics such as what the minimum disturbance due to a quantum measurement is. I will also argue that there are regimes in which weak measurement offers a practical advantage for sensitive measurements.
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
  Institute for Quantum Optics and Quantum Information (IQOQI) - Vienna
May 30, 2013

PIRSA:13050081
Quantum Information

Quantum Fields and Strings
Path Integrals, Reality and Generalizations of Quantum Theory

Adrian Kent
University of Cambridge
May 29, 2013

PIRSA:13050065
Quantum Information

Quantum Foundations
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 Information

Quantum Fields and Strings
Information Theoretic Benefit of Entanglement in Classical Communication Settings

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

PIRSA:13050077
Quantum Information
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 Information
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.
Processing quantum information with relativistic motion of atoms

Eduardo Martin-Martinez
University of Waterloo
May 13, 2013

PIRSA:13050017
Quantum Information
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 Information
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 Information

Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz
Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Information

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
Generalized Relative Entropies, Entanglement Monotones and One-Shot Information Theory	Nilanjana Datta	2013-06-17	Scientific Series	View details
Quantum Factoring with Trapped Ions - A test of scalability	Isaac Chuang	2013-06-12	Scientific Series	View details
Quantum Measurement in the Real World	Aephraim Steinberg	2013-06-05	Scientific Series	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
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
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

Quantum Information

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