Custom Bell inequalities from formal sums of squares

Fuente: arXiv
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Main Authors: Barizien, Victor, Sekatski, Pavel, Bancal, Jean-Daniel
Format: Preprint
Published: 2023
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author Barizien, Victor
Sekatski, Pavel
Bancal, Jean-Daniel
author_facet Barizien, Victor
Sekatski, Pavel
Bancal, Jean-Daniel
contents Bell inequalities play a key role in certifying quantum properties for device-independent quantum information protocols. It is still a major challenge, however, to devise Bell inequalities tailored for an arbitrary given quantum state. Existing approaches based on sums of squares provide results in this direction, but they are restricted by the necessity of first choosing measurement settings suited to the state. Here, we show how the sum of square property can be enforced for an arbitrary target state by making an appropriate choice of nullifiers, which is made possible by leaving freedom in the choice of measurement. Using our method, we construct simple Bell inequalities for several families of quantum states, including partially entangled multipartite GHZ states and qutrit states. In most cases we are able to prove that the constructed Bell inequalities achieve self-testing of the target state. We also use the freedom in the choice of measurement to self-test partially entangled two-qubit states with a family of settings with two parameters. Finally, we show that some statistics can be self-tested with distinct Bell inequalities, hence obtaining new insight on the shape of the set of quantum correlations.
format Preprint
id arxiv_https___arxiv_org_abs_2308_08601
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Custom Bell inequalities from formal sums of squares
Barizien, Victor
Sekatski, Pavel
Bancal, Jean-Daniel
Quantum Physics
Bell inequalities play a key role in certifying quantum properties for device-independent quantum information protocols. It is still a major challenge, however, to devise Bell inequalities tailored for an arbitrary given quantum state. Existing approaches based on sums of squares provide results in this direction, but they are restricted by the necessity of first choosing measurement settings suited to the state. Here, we show how the sum of square property can be enforced for an arbitrary target state by making an appropriate choice of nullifiers, which is made possible by leaving freedom in the choice of measurement. Using our method, we construct simple Bell inequalities for several families of quantum states, including partially entangled multipartite GHZ states and qutrit states. In most cases we are able to prove that the constructed Bell inequalities achieve self-testing of the target state. We also use the freedom in the choice of measurement to self-test partially entangled two-qubit states with a family of settings with two parameters. Finally, we show that some statistics can be self-tested with distinct Bell inequalities, hence obtaining new insight on the shape of the set of quantum correlations.
title Custom Bell inequalities from formal sums of squares
topic Quantum Physics
url https://arxiv.org/abs/2308.08601