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Complications in preparing and preserving quantum correlations stimulate recycling of a single quantum resource in information processing and communication tasks multiple times. Here, we consider a scenario involving multiple independent…

Quantum Physics · Physics 2021-12-30 Debarshi Das , Arkaprabha Ghosal , Ananda G. Maity , Som Kanjilal , Arup Roy

We show that rejection of local realism in quantum mechanics can be tested by Bell-type inequalities for two observers and low-order moments of continuous and unbounded observables. We prove that one requires three observables for each…

Quantum Physics · Physics 2020-12-11 Adam Bednorz

Bob chooses a function from a set of functions and gives Alice the black box that computes it. Alice is to find a characteristic of the function through function evaluations. In the quantum case, the number of function evaluations can be…

Quantum Physics · Physics 2012-11-26 Giuseppe Castagnoli

We consider the problem of steering control for the systems of one spin 1/2 particle and two interacting homonuclear spin 1/2 particles in an electro-magnetic field. The describing models are bilinear systems whose state varies on the Lie…

Quantum Physics · Physics 2007-05-23 D. D'Alessandro

Standard multiparty Bell experiments involve a single source shared by a set of observers. In contrast, network Bell experiments feature multiple independent sources, and each of them may distribute physical systems to a set of observers…

Quantum Physics · Physics 2022-01-05 Sneha Munshi , A. K. Pan

We demonstrate that two spatially separated parties (Alice and Bob) can utilize shared prior quantum entanglement, and classical communications, to establish a synchronized pair of atomic clocks. In contrast to classical synchronization…

Quantum Physics · Physics 2009-11-06 Richard Jozsa , Daniel S. Abrams , Jonathan P. Dowling , Colin P. Williams

The usual representation of quantum algorithms is limited to the process of solving the problem. We extend it to the process of setting the problem. Bob, the problem setter, selects a problem-setting by the initial measurement. Alice, the…

Quantum Physics · Physics 2019-10-23 Giuseppe Castagnoli , Eliahu Cohen , Artur Ekert , Avshalom Elitzur

In [Phys. Rev. Lett. 114, 250401 (2015)] the sharing of non-locality by multiple observers was demonstrated through the quantum violation of Clauser-Horne-Shimony-Halt inequality. In this paper we provide a scheme for sharing of…

Quantum Physics · Physics 2020-01-29 Asmita Kumari , A. K. Pan

We investigate an optimization problem of finding quantum sequential measurements, which forms a wide class of state discrimination problems with the restriction that only sequential measurements are allowed. Sequential measurements from…

Quantum Physics · Physics 2018-03-02 Kenji Nakahira , Kentaro Kato , Tsuyoshi Sasaki Usuda

Many observers can simultaneously measure different parts of an environment of a quantum system in order to find out its state. To study this problem we generalize the formalism of conditional master equations to the multiple observer case.…

Quantum Physics · Physics 2007-05-23 J. Dziarmaga , D. A. R. Dalvit , W. H. Zurek

Linear steering inequalities are useful to check whether a bipartite state is steerable when both the parties are allowed to perform $n$ dichotomic measurements on their parts. In the present study we propose the necessary and sufficient…

Quantum Physics · Physics 2019-08-27 Debarshi Das , Souradeep Sasmal , Arup Roy

Quantum steering describes how local actions on a quantum system can affect another, space-like separated, quantum state. Lately, quantum steering has been formulated also for time-like scenarios and for quantum channels. We approach all…

Quantum Physics · Physics 2018-03-07 Roope Uola , Fabiano Lever , Otfried Gühne , Juha-Pekka Pellonpää

We consider a bipartite scenario where two parties hold ensembles of $1/2$-spins which can only be measured collectively. We give numerical arguments supporting the conjecture that in this scenario no Bell inequality can be violated for…

Quantum Physics · Physics 2019-10-30 Enky Oudot , Jean-Daniel Bancal , Pavel Sekatski , Nicolas Sangouard

It is possible for two parties, Alice and Bob, to establish a secure communication link by sharing an ensemble of entangled particles, and then using these particles to generate a secret key. One way to establish that the particles are…

Quantum Physics · Physics 2018-02-08 M. E. Feldman , G. K. Juul , S. J. van Enk , M. Beck

Quantum steering can be detected via the violation of steering inequalities, which provide sufficient conditions for the steerability of quantum states. Here we discuss the converse problem, namely ensuring that a state is unsteerable, and…

Quantum Physics · Physics 2016-03-21 Joseph Bowles , Flavien Hirsch , Marco Túlio Quintino , Nicolas Brunner

The `no communication' theorem prohibits superluminal communication by showing that any measurement by Alice on an entangled system cannot change the reduced density matrix of Bob's state, and hence the expectation value of any measurement…

Quantum Physics · Physics 2022-09-19 Amitava Datta

Quantum steering is a form of quantum correlation that exhibits an inherent asymmetry, distinguishing it from entanglement and Bell nonlocality. It is now understood that quantum steering plays a pivotal role in asymmetric quantum…

Quantum Physics · Physics 2025-05-28 Jamal El Qars , Ismail Essaoudi , Abdelmajid Ainane

Entanglement is the basic building block of linear optical quantum computation, and as such understanding how to generate it in detail is of great importance for optical architectures. We prove that Bell states cannot be generated using…

Quantum Physics · Physics 2017-11-01 Stasja Stanisic , Noah Linden , Ashley Montanaro , Peter S. Turner

By employing Pauli measurements, we present some nonlinear steering criteria applicable for arbitrary two-qubit quantum systems and optimized ones for symmetric quantum states. These criteria provide sufficient conditions to witness…

Quantum Physics · Physics 2020-10-02 Guo-Zhu Pan , Ming Yang , Hao Yuan , Gang Zhang , Jun-Long Zhao

A simple protocol is described for transferring spatial direction from Alice to Bob (two spatially separated observers) up to inversion. The two observers are assumed to share quantum singlet states and classical communication. The protocol…

Quantum Physics · Physics 2014-08-28 Thomas B. Bahder