We investigate the effect of noise on a class of four-qubit entangled channels for two-qubit teleportation from Alice to Bob. These entangled channels include both parallel Bell pairs and inseparable channels with genuine multipartite entanglement. For the situation where only Bob's share of the entangled channel is subject to decoherence, we show by deriving a general expression for the teleported state that teleportation using noisy inseparable channels is equivalent to teleportation using noisy Bell pairs. When Alice's qubits are also subject to noise, we find that the inseparable channels never give a higher teleportation fidelity than Bell pairs, even in the presence of collective noise. Our results can shed some light on practical two-qubit teleportation.
We investigate the effect of noise on a class of four-qubit entangled channels for two-qubit teleportation from Alice to Bob. These entangled channels include both parallel Bell pairs and inseparable channels with genuine multipartite entanglement. For the situation where only Bob's share of the entangled channel is subject to decoherence, we show by deriving a general expression for the teleported state that teleportation using noisy inseparable channels is equivalent to teleportation using noisy Bell pairs. When Alice's qubits are also subject to noise, we find that the inseparable channels never give a higher teleportation fidelity than Bell pairs, even in the presence of collective noise. Our results can shed some light on practical two-qubit teleportation.
In this work, we consider the following teleportation protocol: There is an arbitrary two-qubit resource state, shared between two spatially separated parties, Alice and Bob. Applying local unitary operators, they transform the resource state into the canonical form. To teleport an unknown qubit, Alice now measures her qubits in the Bell basis. Then, the measurement outcome is communicated by Alice to Bob via noisy classical channel(s). Finally, after receiving the classical message, Bob applies the necessary unitary operator to his qubit. Under this protocol, we find the exact formulae of teleportation fidelity and its deviation. We further find conditions for non-classical fidelity within this protocol. If the classical communication is noiseless in the above protocol then there are resource states which can lead to zero fidelity deviation. However, we show that such states may not lead to zero fidelity deviation when the classical communication is noisy in the same protocol. We also explore the opposite case, i.e., the states, which cannot lead to zero fidelity deviation in the above protocol when the classical communication is noiseless, may lead to zero fidelity deviation when the classical communication is noisy in the same protocol without compromising the non-classical fidelity. Moreover, we exhibit scenarios within the present protocol, where the fidelity deviation increases if the entanglement of the resource state is increased.
Abstract This study discusses the one-way quantum teleportation of 2 qubits through a 4-qubit Bell state channel that is subject to decoherence. Decoherence is one of the unavoidable effects of noise in the transmission process. In the case of quantum teleportation, noise has an impact on the channel, causing changes in its state due to noise. In the absence of noise, teleportation occurs in an ideal state, resulting in a fidelity value of 1, signifying successful information transfer in the ideal scenario. However, when examined in the presence of noise, fidelity is not equal to 1 due to the influence of noise factors and the coefficient of the transmitted state. These noise factors indicate the strength of the noise. The stronger the noise, the lower the fidelity becomes.
In quantum information theory, effects of quantum noise on teleportation are undeniable. Hence,we investigate the effect of noisy channels including amplitude damping, phase damping, depolarizing and phase ip on the teleported state between Alice and Bob where they share an entangled state by using atom-eld interaction state. We analyze the delity and quantum correlations as a function of decoherence rates and time scale of a state to be teleported. We observe that the average delityand quantum correlations accurately depend on types of noise acting on quantum channels. It is found that atom-eld interaction states are affected by amplitude damping channel are more useful for teleportation than when the shared qubites are affected by noisy channels such as AD channel and phase ip. We also observe that if the quantum channels is subject to phase ip noise, the average delity reproduces initial quantum correlations to possible values. On the other hand,not only all the noisy quantum channels do not always destroy average delity but also they can yield the highest delity in noisy conditions. In the current demonstration, our results provide that the average delity can have larger than 2/3 in front of the noise of named other channels with increasing decoherenc strength. Success in quantum states transfer in the present noise establishes the important of studing noisy channels.
Recently, Badziag et al. [Phys. Rev. A 62, 012311 (2000)] obtained a class of noisy states whose teleportation fidelity can be enhanced by subjecting one of the qubits to dissipative interaction with the environment via an amplitude damping channel (ADC). We show that such noisy states result while sharing the states $|{\ensuremath{\Phi}}^{\ifmmode\pm\else\textpm\fi{}}〉=1/\sqrt{2}(|00〉\ifmmode\pm\else\textpm\fi{}|11〉)$ across the ADC. We also show that under similar dissipative interactions, different Bell states give rise to noisy entangled states that are qualitatively very different from each other in the sense that only the noisy entangled states constructed from the Bell states $|{\ensuremath{\Phi}}^{\ifmmode\pm\else\textpm\fi{}}〉$ can sometimes be made better by subjecting the unaffected qubit to a dissipative interaction with the environment. Importantly, if the noisy state is nonteleporting, then it can always be made teleporting with this prescription. We derive the most general restrictions on improvement of such noisy states assuming that the damping parameters are different for both qubits. However, this curious prescription does not work for the noisy entangled states generated from $|{\ensuremath{\Psi}}^{\ifmmode\pm\else\textpm\fi{}}〉=1/\sqrt{2}(|01〉\ifmmode\pm\else\textpm\fi{}|10〉).$ This shows that an a priori knowledge of the noisy channel might be helpful in order to decide which Bell state needs to be shared between Alice and Bob.
We show that the entanglement of the two-qubit teleported state via a class of four-qubit entangled channel states can be increased by collective amplitude damping locally acting on one part of the channel state. Specifically, we compare the entanglement contained in the output state of teleportation before and after the action of the collective amplitude damping on the channel state, and show that for a wide range of input entangled two-qubit states, the local decoherence can result in an increase in the output entanglement. In this process, the average fidelity of the teleportation is also increased. Our result reveals that some quantum properties of the four-qubit channel state are definitely improved in the process of enhancing the fidelity by local noise.
Achieving near-unity fidelity of Quantum Teleportation (QT) in a noisy environment is an essential requirement for its real-world applications. Towards this goal, we devise a distinctive protocol based on the timing of the sender Alice's Bell-basis measurement, synchronous with the suitably engineered structure of noise in the receiver Bob's wing, without requiring any knowledge or manipulation of Alice's local noise. For this purpose, to finally obtain the teleported states by performing the required unitary operations, Bob has to retain his qubits for only two particular Bell-basis outcomes communicated by Alice, whose corresponding reduced states have no dependence on the noise parameters in Alice's wing. Such postselection is crucial for enhancing the fidelity of the teleported state towards its ideal limit, while ensuring its full independence of Alice's noise. We formulate the specifics of our protocol in terms of a generic two-level quantum system, subjected to a general non-Markovian spin-boson model for dephasing noise. The proposed scheme is illustrated by using any pure maximally/non-maximally entangled state as well as a Werner-type mixed state as resource. In particular, using resource states having small values of entanglement measure, we show that the high fidelity of QT is achievable in the presence of noise. Further, using our scheme, considering even the local regime of Werner states, wherein the Bell-CHSH inequalities are not violated, we show that the QT fidelity in the presence of noise can be appreciably high.