Berlin 2024 – scientific programme

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QI: Fachverband Quanteninformation

QI 5: Entanglement Theory

QI 5.7: Talk

Monday, March 18, 2024, 17:00–17:15, HFT-FT 101

Absolute separability witnesses for symmetric multiqubit states — •Eduardo Serrano Ensástiga, Jérôme Denis, and John Martin — Institut de Physique Nucléaire, Atomique et de Spectroscopie, CESAM, University of Liège, B-4000 Liège, Belgium

Entanglement is a valuable resource for quantum applications, and a well-established method for creating entangled multiqubit symmetric states in a controlled manner is the application of a global unitary operation. However, certain states, called symmetric absolutely separable (SAS), remain unentangled after any unitary gate preserving permutation invariance in the constituents of the system. In this work, we develop criteria for detecting SAS states of any number of qubits [1,2]. Our approach is based on the Glauber-Sudarshan P representation for finite-dimensional quantum systems. We introduce families of linear and non-linear SAS witnesses formulated respectively as algebraic inequalities or a quadratic optimization problem. These witnesses are capable of identifying more SAS states than previously known counterparts [3].

[1] E. Serrano-Ensástiga, and J. Martin, Maximum entanglement of mixed symmetric states under unitary transformations, SciPost Phys. 15, 120 (2023).

[2] E. Serrano-Ensástiga, J. Denis and J. Martin, Absolute separability witnesses for symmetric multiqubit states, too appear on arXiv soon.

[3] F. Bohnet-Waldraff, O. Giraud, and D. Braun, Absolutely classical spin states, Phys. Rev. A 95, 012318 (2017).

Keywords: Entanglement; Global unitary transformations; Witnesses