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Fisher information and multiparticle entanglement
TLDR
Bounds on F imply that genuine multiparticle entanglement is needed for reaching the highest sensitivities in quantum interferometry, and these criteria detect different sets of states and illustrate their strengths by considering several examples.
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Experimental detection of multipartite entanglement using witness operators.
TLDR
A canonical way of constructing and decomposing witness operators so that they can be directly implemented with present technology is introduced and applied to three- and four-qubit entangled states of polarized photons, giving experimental evidence that the considered states contain true multipartite entanglement.
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Not all pure entangled states are useful for sub-shot-noise interferometry
We investigate the connection between the shot-noise limit in linear interferometers and particle entanglement. In particular, we ask whether sub-shot-noise sensitivity can be reached with all pure…
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Twin Matter Waves for Interferometry Beyond the Classical Limit
TLDR
This work used spin dynamics in Bose-Einstein condensates to create large ensembles of up to 104 pair-correlated atoms with an interferometric sensitivity beyond the shot noise limit, and points the way toward a new generation of atom interferometers.
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Detection of entanglement with few local measurements
We introduce a general method for the experimental detection of entanglement by performing only few local measurements, assuming some prior knowledge of the density matrix. The idea is based on the…
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Entanglement and sensitivity in precision measurements with states of a fluctuating number of particles.
TLDR
This manuscript generalizes the concepts of separability, entanglement, spin squeezing, and the Heisenberg limit and extends the quantum phase estimation theory by taking into account classical and quantum fluctuations of the particle number.
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Entanglement and extreme spin squeezing for a fluctuating number of indistinguishable particles
We extend the criteria for $k$-particle entanglement from the spin squeezing parameter presented in [A.S. S{\o}rensen and K. M{\o}lmer, Phys. Rev. Lett. {\bf 86}, 4431 (2001)] to systems with a…
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Covariance matrices and the separability problem.
TLDR
This work proposes a unifying approach to the separability problem using covariance matrices of locally measurable observables and leads to insights into the relations between several known entanglement criteria--such as the computable cross-norm and local uncertainty criteria--as well as their limitations.
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Bell inequalities for graph states.
TLDR
A family of Bell inequalities which require three measurement settings for each party and are maximally violated by graph states are derived, showing that for certain types of graph states the violation of these inequalities increases exponentially with the number of qubits.
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Permutationally invariant state reconstruction
TLDR
This work presents an efficient state reconstruction scheme for permutationally invariant quantum state tomography that works for all common state-of-the-art reconstruction principles, including, in particular, maximum likelihood and least squares methods, which are the preferred choices in today's experiments.
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