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 889 - 900 of 1357

Homological Product Codes

Sergey Bravyi IBM (United States)
November 27, 2013

PIRSA:13110091
Quantum Information
Quantum Adversary (Upper) Bound

Shelby Kimmel Massachusetts Institute of Technology (MIT)
November 20, 2013

PIRSA:13110090
Quantum Information
Light and matter: towards macroscopic quantum systems

Jacob Taylor Office of Science and Technology Policy
November 20, 2013

PIRSA:13110060
Quantum Information
Bulk-boundary correspondence in PEPS

Ignacio Cirac Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
November 13, 2013

PIRSA:13110058
Quantum Information
A universal Hamiltonian simulator: the full characterization

Gemma De Las Cuevas Universität Innsbruck
November 11, 2013

PIRSA:13110065
Quantum Information
Asymptotically Optimal Topological Quantum Compiling

Vadym Kliuchnikov University of Waterloo
October 30, 2013

PIRSA:13100129
Quantum Information
Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
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

Homological Product Codes

Sergey Bravyi IBM (United States)
November 27, 2013

PIRSA:13110091
Quantum Information
Quantum codes with low-weight stabilizers known as LDPC codes have been actively studied recently due to their potential applications in fault-tolerant quantum computing. However, all families of quantum LDPC codes known to this date suffer from a poor distance scaling limited by the square-root of the code length. This is in a sharp contrast with the classical case where good families of LDPC codes are known that combine constant encoding rate and linear distance. Here we propose the first family of good quantum codes with low-weight stabilizers. The new codes have a constant encoding rate, linear distance, and stabilizers acting on at most square root of n qubits, where n is the code length. For comparison, all previously known families of good quantum codes have stabilizers of linear weight. Our proof combines two techniques: randomized constructions of good quantum codes and the homological product operation from algebraic topology. We conjecture that similar methods can produce good stabilizer codes with stabilizer weight n^a for any a>0. Finally, we apply the homological product to construct new small codes with low-weight stabilizers. This is a joint work with Matthew Hastings.
Quantum Adversary (Upper) Bound

Shelby Kimmel Massachusetts Institute of Technology (MIT)
November 20, 2013

PIRSA:13110090
Quantum Information
I discuss a technique - the quantum adversary upper bound - that uses the structure of quantum algorithms to gain insight into the quantum query complexity of Boolean functions. Using this bound, I show that there must exist an algorithm for a certain Boolean formula that uses a constant number of queries. Since the method is non-constructive, it does not give information about the form of the algorithm. After describing the technique and applying it to a class of functions, I will outline quantum algorithms that match the non-constructive bound.
Light and matter: towards macroscopic quantum systems

Jacob Taylor Office of Science and Technology Policy
November 20, 2013

PIRSA:13110060
Quantum Information
Advances in quantum engineering and material science are enabling new approaches for building systems that behave quantum mechanically on long time scales and large length scales. I will discuss how microwave and optical technologies in particular are leading to new domains of many-body physics, both classical and quantum, using photons and phonons as the constituent particles. Furthermore, I will highlight practical consequences of these advances, including improved force and acceleration sensing, efficient signal transduction, and topologically robust photonic circuits. Finally, I will consider how such large quantum systems may help us measure and constrain theories of quantum gravity and gravity-induced decoherence.
Bulk-boundary correspondence in PEPS

Ignacio Cirac Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
November 13, 2013

PIRSA:13110058
Quantum Information
TBA
A universal Hamiltonian simulator: the full characterization

Gemma De Las Cuevas Universität Innsbruck
November 11, 2013

PIRSA:13110065
Quantum Information
We show that if the ground state energy problem of a classical spin model is NP-hard, then there exists a choice parameters of the model such that its low energy spectrum coincides with the spectrum of \emph{any} other model, and, furthermore, the corresponding eigenstates match on a subset of its spins. This implies that all spin physics, for example all possible universality classes, arise in a single model. The latter property was recently introduced and called ``Hamiltonian completeness'', and it was shown that several different models had this property. We thus show that Hamiltonian completeness is essentially equivalent to the more familiar complexity-theoretic notion of NP-completeness. Additionally, we also show that Hamiltonian completeness implies that the partition functions are the same. These results allow us to prove that the 2D Ising model with fields is Hamiltonian complete, which is substantially simpler than the previous examples of complete Hamiltonians. Joint work with Toby Cubitt.
Asymptotically Optimal Topological Quantum Compiling

Vadym Kliuchnikov University of Waterloo
October 30, 2013

PIRSA:13100129
Quantum Information
In a topological quantum computer, universality is achieved by braiding and quantum information is natively protected from small local errors. We address the problem of compiling single-qubit quantum operations into braid representations for non-abelian quasiparticles described by the Fibonacci anyon model. We develop a probabilistically polynomial algorithm that outputs a braid pattern to approximate a given single-qubit unitary to a desired precision. We also classify the single-qubit unitaries that can be implemented exactly by a Fibonacci anyon braid pattern and present an efficient algorithm to produce their braid patterns. Our techniques produce braid patterns that meet the uniform asymptotic lower bound on the compiled circuit depth and thus are depth-optimal asymptotically. Our compiled circuits are significantly shorter than those output by prior state-of-the-art methods, resulting in improvements in depth by factors ranging from 20 to 1000 for precisions ranging between 10^{−10} and 10^{−30}.
Simulating Hamiltonian evolution with quantum computers

Richard Cleve Institute for Quantum Computing (IQC)
October 16, 2013

PIRSA:13100097
Quantum Information
In 1982, Richard Feynman proposed the concept of a quantum computer as a means of simulating physical systems that evolve according to the Schrödinger equation. I will explain various quantum algorithms that have been proposed for this simulation problem, including my recent work (jointly with Dominic Berry and Rolando Somma) that significantly improves the running time as a function of the precision of the output data.
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.

Title	Speaker(s)	Date	Talk Type	Info link
Homological Product Codes	Sergey Bravyi	2013-11-27	Scientific Series	View details
Quantum Adversary (Upper) Bound	Shelby Kimmel	2013-11-20	Scientific Series	View details
Light and matter: towards macroscopic quantum systems	Jacob Taylor	2013-11-20	Scientific Series	View details
Bulk-boundary correspondence in PEPS	Ignacio Cirac	2013-11-13	Scientific Series	View details
A universal Hamiltonian simulator: the full characterization	Gemma De Las Cuevas	2013-11-11	Scientific Series	View details
Asymptotically Optimal Topological Quantum Compiling	Vadym Kliuchnikov	2013-10-30	Scientific Series	View details
Simulating Hamiltonian evolution with quantum computers	Richard Cleve	2013-10-16	Scientific Series	View details
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

Quantum Information

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