Efficiency increasing of the bidirectional teleportation protocol via weak and reversal measurements

2022 ◽  
Author(s):  
C. Seida ◽  
A. El Allati ◽  
N. Metwally ◽  
Y. Hassouni

Abstract In this suggested version of the bidirectional teleportation protocol, it is assumed that the used quantum channel passes through an amplitude damping channel. Therefore, some of its quantum correlations (entanglement) are lost and, consequently, its efficiency to implement this protocol decreases. The weak and the reversal measurements are used to recover the losses of these correlations, where the negativity, as a measure of entanglement is improved. In this context, we discussed the effect of the noisy strength on the fidelities of the bidirectional teleported states between the users. It is shown that, by applying the weak and the reversal measurements (WRM) on the initial quantum channel between the users, the fidelities of the teleported states are improved. Moreover, we showed that, the upper bounds of the teleported states depend on the initial states of the triggers and the strengths of WRM. It is worth noting that the WRM improves the quantum correlations of the shared channel and, hence, the fidelity of the teleported state if the initial fidelity of the teleported state is larger than 0.5

2014 ◽  
Vol 14 (11&12) ◽  
pp. 917-936
Author(s):  
Yingkai Ouyang

Evaluating the quantum capacity of quantum channels is an important but difficult problem, even for channels of low input and output dimension. Smith and Smolin showed that the quantum capacity of the Clifford-twirl of a qubit amplitude damping channel (a qubit depolarizing channel) has a quantum capacity that is at most the coherent information of the qubit amplitude damping channel evaluated on the maximally mixed input state. We restrict our attention to obtaining upper bounds on the quantum capacity using a generalization of Smith and Smolin's degradable extension technique. Given a degradable channel $\cN$ and a finite projective group of unitaries $\cV$, we show that the $\cV$-twirl of $\cN$ has a quantum capacity at most the coherent information of $\cN$ maximized over a $\cV$-contracted space of input states. As a consequence, degradable channels that are covariant with respect to diagonal Pauli matrices have quantum capacities that are their coherent information maximized over just the diagonal input states. As an application of our main result, we supply new upper bounds on the quantum capacity of some unital and non-unital channels -- $d$-dimensional depolarizing channels, two-qubit locally symmetric Pauli channels, and shifted qubit depolarizing channels.


2019 ◽  
Vol 33 (14) ◽  
pp. 1950145 ◽  
Author(s):  
Tian-Wen Liu ◽  
Zhi-Yuan He ◽  
Xi-Wen Hou

Girolami and coworkers have proposed measures of quantum correlations and weaving [Girolami et al., Phys. Rev. Lett. 119, 140505 (2017)]. This work derives the analytic time-evolution of such measures and weaving for two kinds of initial states in three qubits under an amplitude-damping and a dephasing noisy environment. It is shown that the 2-partite correlation is forever frozen, which is dependent on an initial state and the property of noise.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peter Brown ◽  
Hamza Fawzi ◽  
Omar Fawzi

AbstractThe rates of quantum cryptographic protocols are usually expressed in terms of a conditional entropy minimized over a certain set of quantum states. In particular, in the device-independent setting, the minimization is over all the quantum states jointly held by the adversary and the parties that are consistent with the statistics that are seen by the parties. Here, we introduce a method to approximate such entropic quantities. Applied to the setting of device-independent randomness generation and quantum key distribution, we obtain improvements on protocol rates in various settings. In particular, we find new upper bounds on the minimal global detection efficiency required to perform device-independent quantum key distribution without additional preprocessing. Furthermore, we show that our construction can be readily combined with the entropy accumulation theorem in order to establish full finite-key security proofs for these protocols.


2015 ◽  
Vol 379 (43-44) ◽  
pp. 2802-2807 ◽  
Author(s):  
WenChao Ma ◽  
Shuai Xu ◽  
Jiadong Shi ◽  
Liu Ye

2019 ◽  
Vol 100 (4) ◽  
Author(s):  
Tanumoy Pramanik ◽  
Young-Wook Cho ◽  
Sang-Wook Han ◽  
Sang-Yun Lee ◽  
Sung Moon ◽  
...  

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