Publications (14)
Four-qubit entangled symmetric states with positive partial transpositions
J. Tura, R. Augusiak, P. Hyllus +3
We solve the open question of the existence of four-qubit entangled symmetric states with positive partial transpositions (PPT states). We reach this goal with two different approa…
Parametric amplification of vacuum fluctuations in a spinor condensate
C. Klempt, O. Topic, G. Gebreyesus +6
Parametric amplification of vacuum fluctuations is crucial in modern quantum optics, enabling the creation of squeezing and entanglement. We demonstrate the parametric amplificatio…
Optimal entanglement witnesses for continuous-variable systems
P. Hyllus, J. Eisert
This paper is concerned with all tests for continuous-variable entanglement that arise from linear combinations of second moments or variances of canonical coordinates, as they are…
Covariance matrices and the separability problem
O. Gühne, P. Hyllus, O. Gittsovich +1
We propose a unifying approach to the separability problem using covariance matrices of locally measurable observables. From a practical point of view, our approach leads to strong…
Entanglement and sensitivity in precision measurements with states of a fluctuating number of particles
P. Hyllus, L. Pezzé, A. Smerzi
The concepts of separability, entanglement, spin-squeezing and Heisenberg limit are central in the theory of quantum enhanced metrology. In the current literature, these are well e…
Estimating multipartite entanglement measures
A. Osterloh, P. Hyllus
We investigate the lower bound obtained from experimental data of a quantum state , as proposed independently by Gühne et al. and Eisert et al. for mixed states of three qubit…
Experimental detection of entanglement via witness operators and local measurements
O. Guehne, P. Hyllus, D. Bruss +4
In this paper we address the problem of detection of entanglement using only few local measurements when some knowledge about the state is given. The idea is based on an optimized…
Multi-resonant spinor dynamics in a Bose-Einstein condensate
C. Klempt, O. Topic, G. Gebreyesus +6
We analyze the spinor dynamics of a Rb-87 F=2 condensate initially prepared in the m_F=0 Zeeman sublevel. We show that this dynamics, characterized by the creation of correlated at…
Resonant spin-changing collisions in spinor Fermi gases
N. Bornemann, P. Hyllus, L. Santos
Spin-changing collisions in trapped Fermi gases may acquire a resonant character due to the compensation of quadratic Zeeman effect and trap energy. These resonances are absent in…
Entanglement properties of composite quantum systems
K. Eckert, O. Gühne, F. Hulpke +6
We present here an overview of our work concerning entanglement properties of composite quantum systems. The characterization of entanglement, i.e. the possibility to assert if a g…
Differential atom interferometry beyond the standard quantum limit
K. Eckert, P. Hyllus, D. Bruss +6
We analyze methods to go beyond the standard quantum limit for a class of atomic interferometers, where the quantity of interest is the difference of phase shifts obtained by two i…
Relations between Entanglement Witnesses and Bell Inequalities
P. Hyllus, O. Guehne, D. Bruss +1
Bell inequalities, considered within quantum mechanics, can be regarded as non-optimal witness operators. We discuss the relationship between such Bell witnesses and general entang…
Complete hierarchies of efficient approximations to problems in entanglement theory
J. Eisert, P. Hyllus, O. Guehne +1
We investigate several problems in entanglement theory from the perspective of convex optimization. This list of problems comprises (A) the decision whether a state is multi-party…
Detection of entanglement with few local measurements
O. Guehne, P. Hyllus, D. Bruss +4
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 ide…