Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review A

Measurement-device-independent entanglement witnesses with imprecise input states

Xingchen Guo, Mao-Sheng Li

Published Mar 21, 2025• 0 citations
Publisher

Abstract

Measurement-device-independent entanglement witnesses (MDI-EWs) enable the detection of entanglement without relying on characterized measurements. However, entanglement criteria for MDI-EWs typically assume the idealized condition that the laboratory input states are precisely the desired ones. In this work, we remove this idealization by considering the realistic scenario in which laboratory input states may be imprecise. We specify a class of MDI-EWs, termed sensitive MDI-EWs, whose entanglement criteria fail under any nonzero imprecision in the input states. We derive sufficient conditions for an MDI-EW to be classified as sensitive, revealing that a large class of MDI-EWs exhibit this sensitivity, consistent with the intuition that sensitive MDI-EWs are common. Additionally, we demonstrate that two well-known MDI-EWs for Werner states are sensitive according to our criteria, one of which recovers the result from a previous study [Phys. Rev. A 104, 012429 (2021)]. Moreover, we clarify the concept of laboratory input states in a way that makes imprecisions experimentally measurable and propose a systematic approach for modifying the criterion of any MDI-EW to accommodate small imprecisions, thus enhancing experimental relevance. A simple MDI-EW example is provided, where our modified criterion is already optimal. This work bridges the gap between idealized theoretical models and practical experimental conditions, paving the way for more robust and accessible entanglement detection in real-world settings.

DOI
10.1103/physreva.111.032426

Related papers

Measurement-device-independent entanglement witness with imprecise input states

X. Guo, Mao-Sheng Li

Measurement-device-independent entanglement witnesses (MDI-EWs) enable the detection of entanglement without relying on characterized measurements. However, the entanglement criteria for MDI-EWs typically assume the idealized condition that the lab input states are precisely the desired ones. In this work, we remove this idealization by considering the realistic scenario in which lab input states may be imprecise. We introduce a new class of MDI-EWs, termed sensitive MDI-EWs, whose entanglement criteria fail under any non-zero imprecision in the input states. We derive sufficient conditions for an MDI-EW to be classified as sensitive, revealing that a large class of MDI-EWs exhibit this sensitivity. Additionally, we demonstrate that two well-known MDI-EWs for Werner states are sensitive according to our criteria, one of which recovers the result from a previous study [Phys. Rev. A 104, 012429 (2021)]. Moreover, we clarify the concept of lab input states in a way that makes imprecisions experimentally measurable, and propose a systematic approach for modifying the criterion of any MDI-EW to accommodate small imprecisions, thus enhancing experimental relevance. A simple MDI-EW example is provided, where our modified criterion is already optimal. This work bridges the gap between idealized theoretical models and practical experimental conditions, paving the way for more robust and accessible entanglement detection in real-world settings.

arXiv:2412.13819•Dec 18, 2024•0 citations

Noisy quantum input loophole in measurement-device-independent entanglement witnesses

Kornikar Sen, Chirag Srivastava, Shiladitya Mal +2 more

Entanglement witnesses form an effective method to locally detect entanglement in the laboratory without having the prior knowledge of the full density matrix. However, separable states can be erroneously indicated as entangled in such detections in the presence of wrong measurements or loss in detectors. Measurement-device-independent entanglement witnesses (MDI-EWs) never detect fake entanglement even under wrong measurements and for a particular kind of lossy detectors. A crucial assumption in the case of faithful detection of entanglement employing MDI-EWs is that the preparation devices producing ``quantum inputs''---which are inputs additional to the quantum state whose entanglement is to be detected---are perfect and there is no noise during their transmission. Here we relax these assumptions and provide a general framework for studying the effect of noise on the quantum inputs, invoking uniform and nonuniform noise models. We derive sufficient conditions on the uniform noisy map for retaining the characteristic of MDI-EWs. We find that in the context of nonuniform and entangling noise, fake entanglement detection is possible even by MDI-EWs. We also investigate various paradigmatic models of local noise and find conditions of revealing entanglement in the class of Werner states.

arXiv:2012.09089•Physical Review A•Jul 30, 2021•7 citations

Measurement-Device-Independent Entanglement Witnesses for All Entangled Quantum States

Cyril Branciard, Denis Rosset, Yeong-Cherng Liang +1 more

The problem of demonstrating entanglement is central to quantum information processing applications. Resorting to standard entanglement witnesses requires one to perfectly trust the implementation of the measurements to be performed on the entangled state, which may be an unjustified assumption. Inspired by the recent work of F. Buscemi [Phys. Rev. Lett. 108, 200401 (2012)], we introduce the concept of measurement-device-independent entanglement witnesses (MDI-EWs), which allow one to demonstrate entanglement of all entangled quantum states with untrusted measurement apparatuses. We show how to systematically obtain such MDI-EWs from standard entanglement witnesses. Our construction leads to MDI-EWs that are loss tolerant and can be implemented with current technology.

arXiv:1210.8037•Physical Review Letters•Feb 6, 2013•169 citations

Resource-Efficient Measurement-Device-Independent Entanglement Witness

E. Verbanis, Anthony Martin, Denis Rosset +3 more

Imperfections in experimental measurement schemes can lead to falsely identifying, or over estimating, entanglement in a quantum system. A recent solution to this is to define schemes that are robust to measurement imperfections-measurement-device-independent entanglement witness (MDI-EW). This approach can be adapted to witness all entangled qubit states for a wide range of physical systems and does not depend on detection efficiencies or classical communication between devices. Here we extend the theory to remove the necessity of prior knowledge about the two-qubit states to be witnessed. Moreover, we tested this model via a novel experimental implementation for MDI-EW that significantly reduces the experimental complexity. By applying it to a bipartite Werner state, we demonstrate the robustness of this approach against noise by witnessing entanglement down to an entangled state fraction close to 0.4.

arXiv:1510.01203•Physical Review Letters•May 9, 2016•43 citations

Closing loopholes of measurement-device-independent nonlinear entanglement witnesses

Kornikar Sen, Chirag Srivastava, Ujjwal Sen

The concept of entanglement witnesses forms a useful technique to detect entanglement in realistic quantum devices. Measurement-device-independent nonlinear entanglement witnesses (MDI-NEWs) are a kind of entanglement witness that eliminates dependence on the correct alignments of measurement devices for guaranteeing the existence of entanglement and also detects more entangled states than its linear counterparts. While this method guarantees entanglement independent of measurement alignments, it is still prone to serving wrong results due to other loopholes. Here, we study the response of MDI-NEWs to two categories of faults occurring in experiments. In the first category, the detection loophole, characterized by lost and additional events of outcomes of measurements, is investigated, and bounds which guarantee entanglement are obtained in terms of the efficiency of measurement being performed. In the second category, we study noise associated with the sets of additional quantum inputs required in MDI-NEW scenarios. In this case, a type of noise is identified which still allows the MDI-NEWs to guarantee entanglement. We also show that MDI-NEWs are less or equally robust in comparison to their linear counterparts under the same noise in additional quantum inputs, although the former group detects a larger volume of entangled states in the noiseless scenario than their linear cousins.

arXiv:2203.07192•Physical Review A•Nov 27, 2023•0 citations

Measurement Device Independent Entanglement Witness of Continuous Variable States

Benjamin Lindegren Larsen, Shuro Izumi, Jonas Schou Neergaard-Nielsen +1 more

We experimentally demonstrated a protocol for measurement device independent entanglement witness (MDI-EW) presented in [1]. A measurement device independent (MDI) protocol will allow two parties (Alice and Bob) to verify that they share an entangled state via the help of trusted input states without making any assumption on the measurement device using only the statistics of the output of the measurement device. Verification of entanglement between states is important as entangled states are a commonly used resource in several aspects of quantum information science such as quantum key distribution. Experimental implementation of MDI-EW in discrete variables have previously been demonstrated in [2], [3].

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 26, 2023•0 citations
Measurement-device-independent entanglement witnesses (MDI-EWs) enable the detection of entanglement without relying on characterized measurements. However, entanglement criteria for MDI-EWs typically assume the idealized condition that the laboratory input states are precisely the desired ones. In this work, we remove this idealization by considering the realistic scenario in which laboratory input states may be imprecise. We specify a class of MDI-EWs, termed sensitive MDI-EWs, whose entanglement criteria fail under any nonzero imprecision in the input states. We derive sufficient conditions for an MDI-EW to be classified as sensitive, revealing that a large class of MDI-EWs exhibit this sensitivity, consistent with the intuition that sensitive MDI-EWs are common. Additionally, we demonstrate that two well-known MDI-EWs for Werner states are sensitive according to our criteria, one of which recovers the result from a previous study [Phys. Rev. A 104, 012429 (2021)]. Moreover, we clarify the concept of laboratory input states in a way that makes imprecisions experimentally measurable and propose a systematic approach for modifying the criterion of any MDI-EW to accommodate small imprecisions, thus enhancing experimental relevance. A simple MDI-EW example is provided, where our modified criterion is already optimal. This work bridges the gap between idealized theoretical models and practical experimental conditions, paving the way for more robust and accessible entanglement detection in real-world settings.
Measurement-device-independent entanglement witnesses (MDI-EWs) enable the detection of entanglement without relying on characterized measurements. However, the entanglement criteria for MDI-EWs typically assume the idealized condition that the lab input states are precisely the desired ones. In this work, we remove this idealization by considering the realistic scenario in which lab input states may be imprecise. We introduce a new class of MDI-EWs, termed sensitive MDI-EWs, whose entanglement criteria fail under any non-zero imprecision in the input states. We derive sufficient conditions for an MDI-EW to be classified as sensitive, revealing that a large class of MDI-EWs exhibit this sensitivity. Additionally, we demonstrate that two well-known MDI-EWs for Werner states are sensitive according to our criteria, one of which recovers the result from a previous study [Phys. Rev. A 104, 012429 (2021)]. Moreover, we clarify the concept of lab input states in a way that makes imprecisions experimentally measurable, and propose a systematic approach for modifying the criterion of any MDI-EW to accommodate small imprecisions, thus enhancing experimental relevance. A simple MDI-EW example is provided, where our modified criterion is already optimal. This work bridges the gap between idealized theoretical models and practical experimental conditions, paving the way for more robust and accessible entanglement detection in real-world settings.
Entanglement witnesses form an effective method to locally detect entanglement in the laboratory without having the prior knowledge of the full density matrix. However, separable states can be erroneously indicated as entangled in such detections in the presence of wrong measurements or loss in detectors. Measurement-device-independent entanglement witnesses (MDI-EWs) never detect fake entanglement even under wrong measurements and for a particular kind of lossy detectors. A crucial assumption in the case of faithful detection of entanglement employing MDI-EWs is that the preparation devices producing ``quantum inputs''---which are inputs additional to the quantum state whose entanglement is to be detected---are perfect and there is no noise during their transmission. Here we relax these assumptions and provide a general framework for studying the effect of noise on the quantum inputs, invoking uniform and nonuniform noise models. We derive sufficient conditions on the uniform noisy map for retaining the characteristic of MDI-EWs. We find that in the context of nonuniform and entangling noise, fake entanglement detection is possible even by MDI-EWs. We also investigate various paradigmatic models of local noise and find conditions of revealing entanglement in the class of Werner states.
The problem of demonstrating entanglement is central to quantum information processing applications. Resorting to standard entanglement witnesses requires one to perfectly trust the implementation of the measurements to be performed on the entangled state, which may be an unjustified assumption. Inspired by the recent work of F. Buscemi [Phys. Rev. Lett. 108, 200401 (2012)], we introduce the concept of measurement-device-independent entanglement witnesses (MDI-EWs), which allow one to demonstrate entanglement of all entangled quantum states with untrusted measurement apparatuses. We show how to systematically obtain such MDI-EWs from standard entanglement witnesses. Our construction leads to MDI-EWs that are loss tolerant and can be implemented with current technology.
Imperfections in experimental measurement schemes can lead to falsely identifying, or over estimating, entanglement in a quantum system. A recent solution to this is to define schemes that are robust to measurement imperfections-measurement-device-independent entanglement witness (MDI-EW). This approach can be adapted to witness all entangled qubit states for a wide range of physical systems and does not depend on detection efficiencies or classical communication between devices. Here we extend the theory to remove the necessity of prior knowledge about the two-qubit states to be witnessed. Moreover, we tested this model via a novel experimental implementation for MDI-EW that significantly reduces the experimental complexity. By applying it to a bipartite Werner state, we demonstrate the robustness of this approach against noise by witnessing entanglement down to an entangled state fraction close to 0.4.
The concept of entanglement witnesses forms a useful technique to detect entanglement in realistic quantum devices. Measurement-device-independent nonlinear entanglement witnesses (MDI-NEWs) are a kind of entanglement witness that eliminates dependence on the correct alignments of measurement devices for guaranteeing the existence of entanglement and also detects more entangled states than its linear counterparts. While this method guarantees entanglement independent of measurement alignments, it is still prone to serving wrong results due to other loopholes. Here, we study the response of MDI-NEWs to two categories of faults occurring in experiments. In the first category, the detection loophole, characterized by lost and additional events of outcomes of measurements, is investigated, and bounds which guarantee entanglement are obtained in terms of the efficiency of measurement being performed. In the second category, we study noise associated with the sets of additional quantum inputs required in MDI-NEW scenarios. In this case, a type of noise is identified which still allows the MDI-NEWs to guarantee entanglement. We also show that MDI-NEWs are less or equally robust in comparison to their linear counterparts under the same noise in additional quantum inputs, although the former group detects a larger volume of entangled states in the noiseless scenario than their linear cousins.
We experimentally demonstrated a protocol for measurement device independent entanglement witness (MDI-EW) presented in [1]. A measurement device independent (MDI) protocol will allow two parties (Alice and Bob) to verify that they share an entangled state via the help of trusted input states without making any assumption on the measurement device using only the statistics of the output of the measurement device. Verification of entanglement between states is important as entangled states are a commonly used resource in several aspects of quantum information science such as quantum key distribution. Experimental implementation of MDI-EW in discrete variables have previously been demonstrated in [2], [3].