Even-parity precession protocol for detecting nonclassicality and entanglement

Abstract

We introduce an even-parity precession protocol that can detect the nonclassicality of some quantum states using only measurements of a uniformly-precessing variable at different points in time. Depending on the system under study, the protocol may detect the Wigner negativity of a single quantum harmonic oscillator or of a single spin $j\ge 2$; the non-Gaussian entanglement of two harmonic oscillators; or genuine multipartite entanglement of a spin ensemble, whose total spin is an integer. Unlike in other nonclassicality tests, simultaneous or sequential measurements are not required. Our protocol can also detect states that commute with the parity operator, which were missed by similar protocols built from Tsirelson's original precession protocol. This work also closes a long-standing gap by showing the possibility of detecting the Greenberger-Horne-Zeilinger entanglement of an even number of qubits using only collective spin measurements.

12 pages, 9 figures (final published version)

References in corpus (14)

• Entanglement detection
• Quantum metrology with nonclassical states of atomic ensembles
• Negativity of the Wigner function as an indicator of nonclassicality
• Leggett-Garg Inequalities
• Sub-Planck spots of Schroedinger cats and quantum decoherence
• Separability criteria for genuine multiparticle entanglement
• Resource theory of quantum non-Gaussianity and Wigner negativity
• Kochen-Specker Contextuality
• Convex resource theory of non-Gaussianity
• Quadratic Bell inequalities as tests for multipartite entanglement
• Dynamics-Based Entanglement Witnesses for Non-Gaussian States of Harmonic Oscillators
• Certifiable Lower Bounds of Wigner Negativity Volume and Non-Gaussian Entanglement with Conditional Displacement Gates
• Leggett-Garg tests for macrorealism in the quantum harmonic oscillator and more general bound systems
• Certification of genuine multipartite entanglement in spin ensembles with measurements of total angular momentum

Cited by in corpus (2)

• All three-angle variants of Tsirelson's precession protocol, and improved bounds for wedge integrals of Wigner functions
• Assessing the dynamical assumptions in Tsirelson inequality tests of non-classicality in harmonic oscillators