Exact quantum circuits for measuring entanglement

Speaker: Dr. Hilary Carteret, University of CalgaryAbstract: There has recently been a lot of interest in techniques for measuring the non-local properties of a density matrix as efficiently as possible. These functions are often defined in terms of unphysical maps, such as the partial transpose. Previous proposed methods for measuring these quantities relied on full state tomography (very inefficient) or the Structural Physical Approximation, which adds large amounts of noise to shift the spectrum of the partially transposed density matrix to be positive, thus incurring a corresponding loss of sensitivity. The moments of the resulting modified density operator are measured using certain sets of generalized Mach-Zehnder interferometers and the spectrum can then be determined using a little algebra.I will show how to construct a family of simple circuits that can determine the spectrum of the partial transpose of a density matrix, without the addition of noise. These circuits depend only on the dimension of the density matrix and do not need any components that are not already required to determine the eigenspectrum of the original density matrix by interferometry. They measure the minimum amount of information required to determine the PT-spectrum completely and they will be exact up to experimental errors.If we get time, I can discuss some extensions to this construction which can be used to measure the concurrence and related entanglement monotones.Bio: Hilary Carteret was born in London, England. She did her D.Phil. in Mathematics at the University of York, working for Tony Sudbery. After six months working in the QOLS group in Imperial College, she moved to Canada, where she has held postdoctoral fellowships at the University of Waterloo (IQC) and then the Universite de Montreal. She has just moved to the new Institute for Quantum Information Science at the University of Calgary, to work with Barry Sanders.Host: Professor Todd A. Brun, tbrun@usc.edu, x. 03503

Location: Hughes Aircraft Electrical Engineering Center (EEB) - -248

Audiences: Everyone Is Invited

Contact: Mayumi Thrasher