Dear All,
This is a reminder that today we have a seminar given by Philippe Faist (ETH Zurich).
Hope to see you there,
cyril
--
Speaker: Philippe Faist (ETH Zurich)
Title: Practical, Reliable Error Bars for Quantum State Tomography
Time: 1:30pm on July 1
Place: 6C-442
Abstract: Which statements can be deduced about the quantum state of a system, given
statistics of outcomes of measurements? Several known methods which directly
estimate the original quantum state are widely used in experiments. However,
these procedures often provide at most loosely justified error bars, or are
specialized to particular measurement settings. Recently, theoretical results
about confidence regions in quantum state space provide a rigourous, albeit
arguably impractical, notion of error bars. In this talk, I will discuss how to
translate these theoretical results into more practical statements which would
be of more interest to an experimenter. We focus on a figure of merit, such as
the fidelity of the quantum state to a target state or to the maximum likelihood
estimate, and numerically produce from the measurement data a posterior
distribution of this figure of merit by exploring the state space with a
Metropolis-Hastings random walk. It turns out that this distribution contains
all the information necessary to deduce reliable error bars for this figure of
merit. In non-extreme cases and for some particular figures of merit, the
distribution is well understood with a theoretical model with few fit
parameters. I will present a new C++ framework designed to implement this task
transparently, along with the analysis of several examples.
--
Cyril Stark
Center for Theoretical Physics
Massachusetts Institute of Technology
77 Massachusetts Ave, 6-304
Cambridge, MA 02139, USA
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