594 citations · 1.7k across the 17 of their papers we have counts for
12 papers · 1 filter
Weak value beyond conditional expectation value of the pointer readings
Lev Vaidman, Alon Ben-Israel, Jan Dziewior +6
It is argued that a weak value of an observable is a robust property of a single pre- and post-selected quantum system rather than a statistical property. During an infinitesimal t…
How long does it take to obtain a physical density matrix?
Lukas Knips, Christian Schwemmer, Nico Klein +3
The statistical nature of measurements alone easily causes unphysical estimates in quantum state tomography. We show that multinomial or Poissonian noise results in eigenvalue dist…
Multipartite entanglement detection with minimal effort
Lukas Knips, Christian Schwemmer, Nico Klein +2
Certifying entanglement of a multipartite state is generally considered as a demanding task. Since an qubit state is parametrized by real numbers, one might naively e…
Genuine Multipartite Entanglement without Multipartite Correlations
Christian Schwemmer, Lukas Knips, Minh Cong Tran +4
Non-classical correlations between measurement results make entanglement the essence of quantum physics and the main resource for quantum information applications. Surprisingly, th…
Experimental Comparison of Efficient Tomography Schemes for a Six-Qubit State
Christian Schwemmer, Geza Toth, Alexander Niggebaum +4
Quantum state tomography suffers from the measurement effort increasing exponentially with the number of qubits. Here, we demonstrate permutationally invariant tomography for which…
Systematic errors in current quantum state tomography tools
Christian Schwemmer, Lukas Knips, Daniel Richart +4
Common tools for obtaining physical density matrices in experimental quantum state tomography are shown here to cause systematic errors. For example, using maximum likelihood or le…
Optimized state independent entanglement detection based on geometrical threshold criterion
Wieslaw Laskowski, Christian Schwemmer, Daniel Richart +3
Experimental procedures are presented for the rapid detection of entanglement of unknown arbitrary quantum states. The methods are based on the entanglement criterion using accessi…
Permutationally invariant state reconstruction
Tobias Moroder, Philipp Hyllus, Geza Toth +5
Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, also an efficient way to reconstruct the density operator fro…
Experimental Schmidt Decomposition and Entanglement Detection
Wieslaw Laskowski, Daniel Richart, Christian Schwemmer +2
We introduce an experimental procedure for the detection of quantum entanglement of an unknown quantum state with as few measurements as possible. The method requires neither a pri…
Useful Multiparticle Entanglement and Sub-Shot-Noise Sensitivity in Experimental Phase Estimation
Roland Krischek, Christian Schwemmer, Witlef Wieczorek +4
We experimentally demonstrate a general criterion to identify entangled states useful for the estimation of an unknown phase shift with a sensitivity higher than the shot-noise lim…
Fisher information and multiparticle entanglement
Philipp Hyllus, Wiesław Laskowski, Roland Krischek +5
The Fisher information gives a limit to the ultimate precision achievable in a phase estimation protocol. It has been shown recently that the Fisher information for a linear tw…
Permutationally invariant quantum tomography
Geza Toth, Witlef Wieczorek, David Gross +3
We present a scalable method for the tomography of large multiqubit quantum registers. It acquires information about the permutationally invariant part of the density operator, whi…