on 30-10-2015
Hendrik Bluhm, Aachen University
30/10/2015, 14:00
Room P9, Mathematics Building, IST
GaAs based quantum dots have played a pioneering role in the experimental development of electron spin qubits. However, one challenge is decoherence due to the unavoidable interaction of the electrons with nuclear spins.
I will discuss experiments that elucidate the role of quadrupolar coupling and g-factor anisotropy for this decoherence channel and thus complete our understanding of the intricate dynamics arising from the coupling to nuclear spins, known as the central spin problem. Contrary to what one might expect when considering spin diffusion, we find that quadrupolar effect degrade coherence via decorrelating transverse nuclear field that are coupled to the electron in second order.
In a second part, I will discuss how careful tuning of gate operations can lead to high gate fidelities (>98% experimentally, >99.8% predicted based on best measured coherence time) in the face of real life experimental constraints. Our feedback-based tuning method is of particular relevance for encoded spin qubits that employ several spins to encode a single qubit in order to simplify control or decoherence suppression as these are often not well suited for standard Rabi control.
I will conclude with an outlook of how a scalable quantum computer based on semiconductor spin qubits might look like and what challenges have to be overcome to reach that long term goal.
Quantum Computation and Information Seminar
http://math.tecnico.ulisboa.pt/seminars/qci/index.php.en?action=next
Support: Phys-Info (IT), SQIG (IT), CFIF and CAMGSD, with support from FCT, FEDER and EU FP7, namely via the Doctoral Programme in the Physics and Mathematics of Information (DP-PMI), and projects PEst-OE/EEI/LA0008/2013, QuSim, QUTE-EUROPE (GA 600788), Landauer (318287) and PAPETS (323901).
More Information..
on 23-10-2015
Martin Plenio, Ulm University
Friday 23/10/2015, at 14:00
Room P9, Mathematics Building, IST
The exploration of quantum effects in biology is an emerging field of research that concerns itself with the experimental and theoretical exploration of quantum phenomena in biological systems. In this lecture I aim to bring out design principles that nature may be exploiting to make use of quantum effects and I will develop in particular one underlying theme - the dynamics of quantum dynamical networks in the presence of an environment and the fruitful interplay that the two may enter. I will aim to demonstrate that this interplay has a wider relevance for biology.
Quantum Computation and Information Seminar
http://math.tecnico.ulisboa.pt/seminars/qci/index.php.en?action=next
Support: Phys-Info (IT), SQIG (IT), CFIF and CAMGSD, with support from FCT, FEDER and EU FP7, namely via the Doctoral Programme in the Physics and Mathematics of Information (DP-PMI), and projects PEst-OE/EEI/LA0008/2013, QuSim, QUTE-EUROPE (GA 600788), Landauer (318287) and PAPETS (323901).
More Information..