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Thursday, March 9, 2017 10:30 am - 10:30 am EST (GMT -05:00)

Seminar: Shalev Ben-David

The Power of Randomized and Quantum Computation

Shalev Ben-David, Massachusetts Institute of Technology

Randomized and quantum computing offer potential improvements over deterministic algorithms, and challenge our notion of what should be considered efficient computation. A fundamental question in complexity theory is to try to understand when these resources help; on which tasks do randomized or quantum algorithms outperform deterministic ones?

In this talk, I will describe some of my work investigating this question, primarily in the query complexity (blackbox) model.

Friday, March 10, 2017 11:45 am - 11:45 am EST (GMT -05:00)

RAC1 Journal Club/Seminar Series:

Fabrication of Diamond Based Fabry-Perot Cavities: Boring is beautiful

Madelaine Liddy, IQC

Nitrogen-vacancy (NV) centers in diamond are promising candidates for acting as the nodes in a quantum network. Previous work has demonstrated the entanglement between two NV centers over a distance of 1.3km for the loophole-free bell test in 2015.

Monday, March 13, 2017 2:30 pm - 2:30 pm EDT (GMT -04:00)

Colloquium: David Allcock

Trapped-ion quantum logic with near-field microwave-driven gates

David Allcock, National Institute of Standards and Technology, Boulder

Hyperfine qubits in laser-cooled trapped atomic ions are one of the most promising platforms for general-purpose quantum computing. Magnetic field-insensitive ‘clock states’ and near-infinite lifetimes allow for minute-long memory coherence times as well as qubit frequencies that are in the convenient microwave domain [1]. Most work on these qubits has so far focussed on using lasers for gate operations, however there are several schemes that offer the prospect of performing all coherent operations using purely electronic methods [2,3].

Tuesday, March 14, 2017 10:00 am - 10:00 am EDT (GMT -04:00)

Seminar: Leena Aggarwal

Tip induced superconductivity at mesoscopic point contacts on topological semimetals

Leena Aggarwal, Indian Institute of Science Education and Research, Mohali

I will present the observation of a new phase of matter, tip-induced superconductivity (TISC), that emerges only under mesoscopic metallic point contacts on topologically non-trivial semimetals like a 3-D Dirac semimetal Cd3As2, and a Weyl semimetal, TaAs. From theoretical considerations, it is believed that such semimetals exist near topological phase boundaries.

Monday, March 20, 2017 2:30 pm - 2:30 pm EDT (GMT -04:00)

Seminar: Rakesh Tiwari

Robust quantum optimizer with full connectivity

Rakesh Tiwari, McGill University

Quantum phenomena have the potential to speed up the solution of hard optimization problems. For example quantum annealing, based on the quantum tunneling effect, has recently been shown to scale exponentially better with system size as compared with classical simulated annealing. However, current realizations of quantum annealers with superconducting qubits face two major challenges. First, the connectivity between the qubits is limited, excluding many optimization problems from a direct implementation.

Wednesday, March 22, 2017 11:00 am - 11:00 am EDT (GMT -04:00)

Seminar: Mohammad Ansari

Entropy measurement in quantum systems

Dr. Mohammad Ansari, Peter Grünberg Institute, and Jülich-Aachen Research Alliance Institute (JARA)

Entropy is an important information measure. A complete understanding of entropy flow will have applications in quantum thermodynamics and beyond; for example it may help to identify the sources of fidelity loss in quantum communications and methods to prevent or control them. Being nonlinear in density matrix, its evaluation for quantum systems requires simultaneous evolution of more-than-one density matrix.

Friday, March 24, 2017 11:45 am - 11:45 am EDT (GMT -04:00)

RAC1 Journal Club/Seminar Series - Special Seminar

Optical manipulation of polariton in semiconductor microstructures

Félix Marsault, French National Center for Scientific Research

Cavity polaritons are bosonic quasiparticles arising from the strong coupling between photons and excitons. They can massively occupy a single quantum state in the regime of polariton lasing [1], showing particular properties such as long coherence times [1], long range spatial coherence [1] and a linearly polarized emission [1,2,3]. Moreover, they possess strong excitonic nonlinearities and thus provide a new platform for elliptical photonic manipulation, with the demonstration of a polariton spin switch [4], polariton transistors [5] and the proposal of other proof-of-principle operations for elliptical integrated logic circuits [6].

Monday, March 27, 2017 2:30 pm - 2:30 pm EDT (GMT -04:00)

Colloquium: Thomas Vidick

Rigorous RG algorithms and area laws for low energy eigenstates in 1D

Thomas Vidick, California Institute of Technology

One of the central challenges in the study of quantum many-body systems is the complexity of simulating them on a classical computer. We give a new algorithm for finding low energy states for 1D systems, based on a rigorously justified RG type transformation.

Monday, April 3, 2017 2:30 pm - 2:30 pm EDT (GMT -04:00)

Colloquium: Kin Fai Mak

Superconductivity in single-layer NbSe2

Kin Fai Mak, Pennsylvania State University

The discovery of graphene has stimulated not only the field of carbon nanoelectronics, but also studies of novel electronic phenomena in a wide range of atomically thin van der Waals’ materials. In this talk, I will discuss our recent effort in the isolation of a single layer of niobium diselenide (NbSe2), a new non-centrosymmetric superconductor.

Friday, April 7, 2017 11:45 am - 11:45 am EDT (GMT -04:00)

RAC1 Journal Club/Seminar Series

The puzzle of genuine multiparticle interference

Sascha Agne, IQC

Two recent experiments demonstrate access to a new realm of quantum phenomena called genuine multiparticle interference. For three photons this means that interference between all three photons is observed while, simultaneously, neither pairs nor single photons display interference.