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Device-independent quantum key distribution aims to provide key distribution schemes whose security is based on the laws of quantum physics but which does not require any assumptions about the internal working of the quantum devices used in…

Quantum Physics · Physics 2011-03-18 Lluis Masanes , Stefano Pironio , Antonio Acin

The certification of quantum resources is a critical tool in the development of quantum information processing. In particular, quantum state verification is a fundamental building block for communication and computation applications,…

Our common understanding of the physical world deeply relies on the notion that events are ordered with respect to some time parameter, with past events serving as causes for future ones. Nonetheless, it was recently found that it is…

In quantum mechanics events can happen in no definite causal order: in practice this can be verified by measuring a causal witness, in the same way that an entanglement witness verifies entanglement. Indefinite causal order can be observed…

Quantum Physics · Physics 2018-11-05 K. Goswami , C. Giarmatzi , M. Kewming , F. Costa , C. Branciard , J. Romero , A. G. White

Secure and reliable certification of quantum resources is a fundamental challenge in the advancement of next-generation quantum technologies, particularly as devices become more complex and integrated into practical applications, where…

Indefinite causal order is an evolving field with potential involvement in quantum technologies. Here we propose and study one possible scenario of practical application in quantum communication: a compound entanglement distillation…

Quantum Physics · Physics 2023-12-08 Zai Zuo , Michael Hanks , M. S. Kim

Quantum measurements under realistic conditions reveal only partial information about a system. Yet, by performing sequential measurements on the same system, additional information can be accessed. We investigate this problem in the…

Quantum Physics · Physics 2025-10-23 Carles Roch I Carceller , Hanwool Lee , Jonatan Bohr Brask , Kieran Flatt , Joonwoo Bae

Quantum theory is in principle compatible with scenarios where physical processes occur in an indefinite order, potentially yielding advantages in a broad range of information processing tasks. However, advantages in communication, the most…

Quantum Physics · Physics 2026-03-26 Xuanqiang Zhao , Benchi Zhao , Cyril Branciard , Giulio Chiribella

Classically the causal order of two timelike separated events A and B is fixed -- either A before B or B before A. This is no longer true in quantum theory, where it is possible to encounter superpositions of causal orders. The quantum…

Certification of quantum devices received from unknown providers is a primary requirement before utilizing the devices for any information processing task. Here, we establish a protocol for certification of a particular set of $d$-outcome…

Quantum Physics · Physics 2022-05-20 Debarshi Das , Ananda G. Maity , Debashis Saha , A. S. Majumdar

Operations performing on quantum batteries are extended to scenarios where we no longer force the existence of definite causal order of occurrence between distinct processes. In contrast to standard theories, the so called indefinite causal…

Quantum Physics · Physics 2021-05-27 Yuanbo Chen , Yoshihiko Hasegawa

Nonlocal correlations are useful for device independent (DI) randomness certification [Nature (London) {\bf 464}, 1021 (2010)]. The advantage of this DI protocol over the conventional quantum protocol is that randomness can be certified…

Quantum Physics · Physics 2016-09-23 Anubhav Chaturvedi , Manik Banik

This letter further explores the recent scheme of switched quantum channels with indefinite causal order applied to the reference metrological task of quantum phase estimation in the presence of noise. We especially extend the explorations,…

Quantum Physics · Physics 2023-12-06 Francois Chapeau-Blondeau

Causal nonseparability refers to processes where events take place in a coherent superposition of different causal orders. These may be the key resource for experimental violations of causal inequalities and have been recently identified as…

Quantum Physics · Physics 2019-12-16 Márcio M. Taddei , Ranieri V. Nery , Leandro Aolita

In practical situations, the reliability of quantum resources can be compromised due to complex generation processes or adversarial manipulations during transmission. Consequently, the trials generated sequentially in an experiment may…

Quantum Physics · Physics 2026-02-10 Yanbao Zhang , Akshay Seshadri , Emanuel Knill

The quantum switch has been widely studied as a prototypical example of indefinite causal order in quantum information processing. However, the potential advantages of utilising more general forms of indefinite causal orders remain largely…

Quantum Physics · Physics 2025-01-24 Spiros Kechrimparis , James Moran , Hyukjoon Kwon

The emergence of quantum theory at the beginning of 20$-th$ century has changed our view of the microscopic world and has led to applications such as quantum teleportation, quantum random number generation and quantum computation to name a…

Quantum Physics · Physics 2023-02-03 Shubhayan Sarkar

A major challenge in quantum communication is addressing the negative effects of noise on channel capacity, especially for completely depolarizing channels, where information transmission is inherently impossible. The concept of indefinite…

Quantum mechanics allows for coherent control over the order in which different processes take place on a target system, giving rise to a new feature known as indefinite causal order. Indefinite causal order provides a resource for quantum…

Recently, the possible existence of quantum processes with indefinite causal order has been extensively discussed, in particular using the formalism of process matrices. Here we give a new perspective on this question, by establishing a…