Events

Efficient Quantum Algorithms for Simulating Lindblad Evolution

Chunhao Wang

The Lindblad equation is the natural generalization to open systems of the Schrödinger equation. We give a quantum algorithm for simulating the evolution of an n-qubit system under the Lindblad equation with local terms. The gate cost of the algorithm is O(mTlog^2(T/\epsilon)/loglog(T/\epsilon)), where T is the evolution time, \epsilon is the precision of the output state, and m is the number of local terms occurring in the equation.

Graphs and Multi-mode Coupling: How to build a programmable, directional parametric amplifier

Jose Aumentado, National Institute of Standards and Technology, Boulder

Parametric amplification is a big deal these days, especially for research in superconducting quantum information. This is because, in principle, parametric amplifiers can amplify a signal while adding the minimum amount of noise that quantum mechanics allows. In practice, the situation is a little more complicated and the practical measurement chains can degrade this ideal performance.

Entanglement and Purcell Effects in Systems for Quantum Information and Sensing

Stephen K. Gray, Argonne National Laboratory

I discuss how to propagate the quantum mechanical density matrix, including dephasing, spontaneous emission and dissipation for systems relevant to quantum information and sensing. Two applications are then presented. In the first example, a plasmonic system is coupled to quantum dots. The plasmonic system could be a single metal nanoparticle or an array of metal nanoparticles and can be viewed as an optical resonator.

Dicke's Superradiance in Astrophysics

Fereshteh Rajabi, University of Western Ontario

It is generally assumed that in the interstellar medium much of the emission emanating from atomic and molecular transitions within a radiating gas happen independently for each atom or molecule, but as was pointed out by R. H. Dicke in a seminal paper several decades ago this assumption does not apply in all conditions. As will be discussed in my presentation, and following Dicke's original analysis, closely packed atoms/molecules can interact with their common electromagnetic field and radiate coherently through an effect he named superradiance.

Structured Hadamard matrices and quantum information

Karol Zyczkowski, Jagiellonian University, Poland

Two classes of complex Hadamard matrices with certain special properties found recently applications in quantum physics. Consider a four index tensor $T_{ijkl}$ of size M. It can be reshaped into a square matrix $A_{\mu,\nu}$ of size $M^2$ with three different choices of composed indices e.g. $\mu=(i,j); \nu=(k,l)$ or $\mu=(i,k); \nu=(j,l)$, or $\mu=(i,l); \nu=(j,k)$.

Exponential Separation between Quantum Communication Complexity and Classical Information Complexity

Dave Touchette, IQC

We exhibit a Boolean function for which the quantum communication complexity is exponentially larger than the classical information complexity. An exponential separation in the other direction was already known from the work of Kerenidis et. al. [SICOMP 44, pp. 1550--1572], hence our work implies that these two complexity measures are incomparable. As classical information complexity is an upper bound on quantum information complexity, which in turn is equal to amortized quantum communication complexity, our work implies that a tight direct sum result for distributional quantum communication complexity cannot hold.

Greg Holloway of the Department of Physics and Astronomy is defending his thesis:

Electron transport in semiconducting nanowires and quantum dots

Greg is supervised by Associate Professor Joanthan Baugh.

NMR 'diffraction' in solids

Holger Haas, IQC

Peter Mansfield and Peter Grannell discussed the possibility of NMR crystallography in their 1973 seminal paper 'NMR 'diffraction' in solids?', however, an experimental realisation of NMR 'diffraction' is yet to be demonstrated. I will discuss the feasibility of NMR crystallography in the light of recent advances in nanoscale MRI which combine numerical control finding algorithms and state of the art force detected magnetic resonance techniques.

Matthew Graydon of the Department of Physics and Astronomy is defending his thesis:

Conical Designs and Categorical Jordan Algebraic Post-Quantum Theories

Matthew is supervised by Associate Professor Kevin Resch and Rob Spekkens (Perimeter Institute for Theoretical Physics).

Two-dimensional coherent photocurrent excitation spectroscopy of a hybrid lead-halide perovskite solar cell

Carlos Silva, Université de Montréal

Hybrid halide perovskite (for example, CH3NH3PbI3) solar cells now display solar power conversion efficiencies exceeding 20% [1]. In these materials, excitonic and free-carrier regimes of primary photoexcitations are possible depending on crystalline microstructure of the active layer and excitation density [2].