Entanglement detection

  title={Entanglement detection},
  author={Otfried Guhne and G{\'e}za T{\'o}th},

What Criterion Can We Get From Precise Entanglement Witnesses?

A thorough study of a three-qubit Greenberger-Horne-Zeilinger (GHZ) state mixed with a W state and white noise finds a connection between Wootters formula and the matched entanglement witness.

Detecting entanglement of unknown quantum states with random measurements

This work investigates the use of random local measurements, from which entanglement witnesses are then constructed via semidefinite programming methods, and proposes a scheme of successively increasing the number of measurements until the presence ofEntanglement can be unambiguously concluded.

Quantitative entanglement witnesses of isotropic and Werner classes via local measurements

Quantitative entanglement witnesses allow one to bound the entanglement present in a system by acquiring a single expectation value. In this paper, we analyze a special class of such observables

Minimal Entanglement Witness from Electrical Current Correlations.

It is found that all entangled pure states, but not all mixed ones, can be detected with only two measurements, except the maximally entangled states, which require three measurements.

Nonlinear improvement of qubit-qudit entanglement witnesses

The entanglement witness is an important and experimentally applicable tool for entanglement detection. In this paper, we provide a nonlinear improvement of any entanglement witness for $2\otimes d$

Entanglement Detection by Violations of Noisy Uncertainty Relations: A Proof of Principle.

This proof-of-principle experiment shows that quantum noise can be successfully handled by a fully quantum model in order to enhance the ability to detect entanglement.

Measurement-device-independent entanglement witnesses for all entangled quantum states.

This work introduces the concept of measurement-device-independent entanglement witnesses (MDI-EWs), which allow one to demonstrateEntanglement of all entangled quantum states with untrusted measurement apparatuses, and shows how to systematically obtain such MDI-ews from standard entangler witnesses.

Geometry of Faithful Entanglement.

This work proves a structural result on the corresponding fidelity-based entanglement witnesses, resulting in a simple condition for faithfulness of a two-party state, and shows that faithful Entanglement is, in a certain sense, usefulEntanglement theory.

Device-Independent Entanglement Detection

Entanglement is one of the most intriguing feature of quantum physics. It allows several particles to be in a state which cannot be understood as a concatenation of the sate of each particle.

Device-Independent Entanglement Certification of All Entangled States.

We present a method to certify the entanglement of all entangled quantum states in a device-independent way. This is achieved by placing the state in a quantum network and constructing a correlation



Estimating entanglement measures in experiments.

It is shown how a lower bound on a genericEntanglement measure can be derived from the measured expectation values of any finite collection of entanglement witnesses, and witness measurements are given a quantitative meaning without the need of further experimental data.

Experimental detection of entanglement via witness operators and local measurements

Abstract 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

Measuring quantum entanglement without prior state reconstruction.

It is shown that, despite strong nonlinearity, entanglement of formation of a two-qubit state can be measured without prior state reconstruction. Collective measurements on a small number of copies

Characterizing Entanglement

Quantum entanglement is at the heart of many tasks in quantum information. Apart from simple cases (low dimensions, few particles, pure states), however, the mathematical structure of entanglement is

Quantitative entanglement witnesses

All these tests—based on the very same data—give rise to quantitative estimates in terms of entanglement measures, and if a test is strongly violated, one can also infer that the state was quantitatively very much entangled, in the bipartite and multipartite setting.

Characterizing entanglement with geometric entanglement witnesses

We show how to detect entangled, bound entangled and separable bipartite quantum states of arbitrary dimension and mixedness using geometric entanglement witnesses. These witnesses are constructed

Geometric entanglement witnesses and bound entanglement

We study entanglement witnesses that can be constructed with regard to the geometrical structure of the Hilbert-Schmidt space, i.e., we present how to use these witnesses in the context of

Entanglement detection by local orthogonal observables.

A family of entanglement witnesses and corresponding positive maps that are not completely positive based on local orthogonal observables that can be physically realized by measuring a Hermitian correlation matrix of local orthosomatic observables.

Novel schemes for directly measuring entanglement of general states.

It is demonstrated that rank-1 local factorizable projective measurements, which are achievable with only one copy of an entangled state involved at a time in a sequential way, are sufficient to directly determine the concurrence of an arbitrary two-qubit entangled state.

Detecting quantum entanglement : entanglement witnesses and uncertainty relations

This thesis deals with methods of the detection of entanglement. After recalling some facts and definitions concerning entanglement and separability, we investigate two methods of the detection of