Seminar

Existence and Uniqueness in the Quantum Marginal Problem

Joel Klassen, IQC

The quantum marginal problem asks whether a family of quantum marginals are compatible with a global quantum state. It is of central importance to a wide range of topics in both quantum many body physics and quantum information. Often it can be the case that when a family of quantum marginals are compatible with a global quantum state, that global state is unique.

Simulation of III-V Nanowires for Infrared Photodetection

Khalifa M. Azizur-Rahman, McMaster University

The absorptance in vertical nanowire (nw) arrays is typically dominated by three optical phenomena: radial mode resonances, near-field evanescent wave coupling, and Fabry–Perot (F-P) mode resonances. The contribution of these optical phenomena to GaAs, InP and InAs nw absorptance was simulated using the finite element method. The study compared the absorptance between finite and semi-infinite nws with varying geometrical parameters, including the nw diameter (D), array period (P), and nw length (L).

Many-Body Localization Through the Lens of Ultracold Quantum Gases

Pranjal Bordia, Max Planck Institute, Munich

A fundamental assumption of quantum statistical mechanics is that closed isolated systems always thermalize under their own dynamics. Progress on the topic of many-body localization has challenged this vital assumption, describing a phase where thermalization, and with it, equilibrium thermodynamics, breaks down.

On-demand entangled photon sources

Arash Ahmadi

In this presentation I will be talking about the project we have done in our group since last October on the emission of a QD embedded in a nano-wire.

Quantum science and technology at QuTech (Delft, NL)

Julia Cramer, QuTech Delft

QuTech is an advanced research center for quantum computing and the quantum internet, addressing scientific and engineering challenges in collaboration with industrial partners. QuTech is striving to remain at the forefront in quantum information science and technology. I’ll give some info on the development of QuTech over the years. Furthermore, I will present what the goals and focusses are of our research teams, current work and latest milestones.

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Chernoff Bound for Quantum Operations is Faithful

Nengkun Yu, Tsinghua University & University of Technology, Sydney

We consider the problem of testing two quantum hypotheses of quantum operations in the setting of many uses where an arbitrary prior distribution is given. The concept of the Chernoff bound for quantum operations is investigated to track the minimal average probability of error of discriminating two quantum operations asymptotically.

Mode-selection, purification, and ultrafast manipulation of quantum light with nonlinear waveguide devices

John Donohue, University of Paderborn

The temporal structure of quantum light offers an intrinsically high-dimensional and robust platform for encoding quantum information. In particular, the time-frequency degree of freedom can be explored in the frame of pulsed temporal modes, the ultrafast analogy to spatial Hermite-Gauss or orbital angular momentum modes. These overlapping temporal modes are naturally compatible with waveguide devices and fibre infrastructure, but present unique challenges to fully explore and exploit.

A platform to study many-body physics with photons

Hakan Tureci, Princeton University

The past decade has seen enormous experimental progress in building superconducting electrical circuits featuring artificial atoms subject to the quantized electromagnetic field of microwave photons. The fabrication and control of superconducting circuits has reached a stage where many such elements can be wired up into intricate networks, allowing the preparation and readout of complex quantum states of photons and atoms.

The optimality of projections for quantum state exclusion

Abel Molina, IQC

We will first motivate the problem of quantum state exclusion of pure states, through its connections with the PBR game and with compatibility conditions for quantum state assignments. Then, we will discuss our recent result regarding the optimality of projections for perfect state exclusion of 3 pure states in 3 dimensions (arXiv:1702.06449).

Dephasing with strings attached

Leonid Pryadko, University of California, Riverside

Is there a difference between the quantum dynamics of a "real" particle and a collective excitation, like that in a spin ice, which creates a measurable gauge field? I will argue that in the presence of weak dephasing, the answer depends on the quantity measured.