Quantum Steering Beyond Instrumental Causal Networks

Nery, Ranieri; Taddei, M. M.; Chaves, Rafael; Aolita, Leandro

doi:10.1103/physrevlett.120.140408

Cited by 17 publications

(19 citation statements)

References 72 publications

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“…As shown in Refs. [23,[25][26][27], even if one imposes the instrumental causal structure to a quantum experiment, still some instrumental inequalities can be violated. This can be seen as a stronger version of Bell's theorem [20], showing that correlations mediated via quantum entanglement can fail to have a description in terms of standard causal models.…”

Section: Relaxing the Independence Assumptionmentioning

confidence: 99%

Causal inference with imperfect instrumental variables

Miklin¹,

Gachechiladze²,

Moreno³

et al. 2021

Preprint

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Instrumental variables allow for quantification of cause and effect relationships even in the absence of interventions. To achieve this, a number of causal assumptions must be met, the most important of which is the independence assumption, which states that the instrument and any confounding factor must be independent. However, if this independence condition is not met, can we still work with imperfect instrumental variables? Imperfect instruments can manifest themselves by violations of the instrumental inequalities that constrain the set of correlations in the scenario. In this paper, we establish a quantitative relationship between such violations of instrumental inequalities and the minimal amount of measurement dependence required to explain them. As a result, we provide adapted inequalities that are valid in the presence of a relaxed measurement dependence assumption in the instrumental scenario. This allows for the adaptation of existing and new lower bounds on the average causal effect for instrumental scenarios with binary outcomes. Finally, we discuss our findings in the context of quantum mechanics.

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Section: Relaxing the Independence Assumptionmentioning

confidence: 99%

Causal inference with imperfect instrumental variables

Miklin¹,

Gachechiladze²,

Moreno³

et al. 2021

Preprint

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“…-We now consider the instrumental steering scenario [24]. In this case, Bob still has an input that can inform the preparation of a quantum system, however now this input can depend on Alice's measurement outcome (see Fig.…”

mentioning

confidence: 99%

“…1(d), except that Bob's system is a classical variable. Previously, classical-quantum gaps had been found in Belltype [25,26,33] and steering [24] scenarios. Furthermore, quantum-post-quantum gaps have also been found in Belltype scenarios [25,26]; but the existence of post-quantum instrumental steering remained an open question.…”

mentioning

confidence: 99%

Bipartite Postquantum Steering in Generalized Scenarios

et al. 2020

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The study of stronger-than-quantum effects is a fruitful line of research that provides valuable insight into quantum theory. Unfortunately, traditional bipartite steering scenarios can always be explained by quantum theory. Here we show that, by relaxing this traditional setup, bipartite steering incompatible with quantum theory is possible. The two scenarios we describe, which still feature Alice remotely steering Bob's system, are: (i) one where Bob also has an input and operates on his subsystem, and (ii) the 'instrumental steering' scenario. We show that such bipartite post-quantum steering is a genuinely new type of post-quantum nonlocality, which does not follow from post-quantum Bell nonlocality.

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“…To that end, several attempts have already been made to understand quantum nonlocality [25][26][27][28][29][30][31], contextuality [32] and EPR-nonlocality [33] relaxing the stricter notion of ordered causal relation. In this regard, the quantum instrumental causal network is one of the most promising structure of causal models.…”

mentioning

confidence: 99%

“…Instead of the traditional ordered causal network, search for various new quantum causal models has drawn quite a bit of attention [33][34][35][36] in the last few years and the model, 'instrumental causal network' turns out to be the most prominent candidate in this regard. It may be considered as a relaxed version of our day-to-day observation of cause and effect relationship.…”

mentioning

confidence: 99%

No nonlocal advantage of quantum coherence beyond quantum instrumentality

Mondal,

Singh,

Kaszlikowski

2019

Preprint

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Recently, it was shown that quantum steerability is stronger than the bound set by the instrumental causal network. This implies, quantum instrumentality cannot simulate EPR-nonlocal correlations completely. In contrast, here we show that quantum instrumentality can indeed simulate EPR correlations completely and uniquely if viewed from the perspective of NAQC. Implication of our result is that the entire set of EPR-correlations can be explained by the LHS model in the instrumental causal background if viewed from the perspective of NAQC.

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Quantum Steering Beyond Instrumental Causal Networks

Cited by 17 publications

References 72 publications

Causal inference with imperfect instrumental variables

Causal inference with imperfect instrumental variables

Bipartite Postquantum Steering in Generalized Scenarios

No nonlocal advantage of quantum coherence beyond quantum instrumentality

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