We propose a quantum state protection scheme via quantum feedforward control combined with environment-assisted measurement to protect arbitrary unknown initial states from the finite-temperature thermal noise (FTTN). The main strategy is to transfer the quantum system to a noise-robust state by weak measurement and feedforward control before the noise channel. Then we apply the environment-assisted measurement on the noise channel to select our desired damped states that are invertible to the initial state. After the noise channel, the reversal operations are applied to restore the initial state. We consider the protection of a single-qubit system, derive the analytical expressions of the success probability and the fidelity, and analyze the influence of key parameters on the performance of the proposed scheme. Unlike previous studies, there is no trade-off between the fidelity and the success probability in the proposed scheme; hence one could maximize them separately. Simulation results show that the proposed scheme can greatly improve the fidelity of the quantum state with a certain success probability. Moreover, the proposed scheme is successfully applied to improving the fidelity of controlled quantum teleportation through two independent FTTN channels from the perspective of protecting the shared entanglement.
We propose a quantum state protection scheme via quantum feedforward control combined with environment-assisted measurement to protect arbitrary unknown initial states from the finite-temperature thermal noise (FTTN). The main strategy is to transfer the quantum system to a noise-robust state by weak measurement and feedforward control before the noise channel. Then we apply the environment-assisted measurement on the noise channel to select our desired damped states that are invertible to the initial state. After the noise channel, the reversal operations are applied to restore the initial state. We consider the protection of a single-qubit system, derive the analytical expressions of the success probability and the fidelity, and analyze the influence of key parameters on the performance of the proposed scheme. Unlike previous studies, there is no trade-off between the fidelity and the success probability in the proposed scheme; hence one could maximize them separately. Simulation results show that the proposed scheme can greatly improve the fidelity of the quantum state with a certain success probability. Moreover, the proposed scheme is successfully applied to improving the fidelity of controlled quantum teleportation through two independent FTTN channels from the perspective of protecting the shared entanglement.
This paper presents a tripartite quantum teleportation protocol that incorporates feed-forward control and environment-assisted measurement, aiming to suppress the influence of arbitrary noise with at least one reversible Kraus operator. In this protocol, the feed-forward control is first utilized before the decoherence channel, such that the entangled qubit is transferred to the target state, which is more robust against noise. Next, the measurement is performed on the noise environment coupled with the entangled qubit during the decoherence channel. Finally, the reversed feed-forward control and the redesigned weak measurement reversal operator are applied after the decoherence channel. This protocol can be applied to the case where both amplitude damping and phase damping noise coexist. Based on this protocol, the analytical expressions for performance metrics including the average fidelity and the success probability are further derived. Even for the heavy damping cases, the final average teleportation fidelity can reach 1, which is independent of the magnitude of decoherence and the entanglement parameters. Furthermore, we optimize the success probability without compromising fidelity, and derive the average fidelity expression of the standard tripartite teleportation protocol through the phase damping noise channel. The effectiveness of our protocol is verified by numerical simulations.
Abstract Noiseless quantum channels are critical to share a pure maximally entangled state for performing an ideal teleportation protocol. However, in reality the shared entanglement severely degraded due to decoherence. In this paper, we propose a quantum teleportation channel protection scheme to enhance the teleportation fidelity in presence of decoherence. Before the entangled pair enters the decoherence channel, the weak measurement and flip operations are applied to transfer the qubit to a more robust state to the effects of the noise. After the decoherence channel the reversed flip operations and weak measurement reversal are applied to recover the initial state. We illustrate our protected teleportation scheme and compare it with a protocol based on weak measurement reversal. The numerical results show that the average teleportation fidelity of our proposed scheme can be significantly improved. Although the proposed entanglement protection scheme is probabilistic, after a successful entanglement transmission, we use the standard teleportation protocol which has probability one.
Quantum teleportation as a key protocol for quantum communication and quantum computing demonstrates the stark difference between quantum and classical information transmission. An ideal teleportation protocol requires pure maximally entangled state as the teleportation channel, while in real implementations the shared entanglement is severely degraded due to decoherence. In this letter, we propose a scheme to protect the quantum teleportation from decoherence by means of environment assisted measurement with weak measurements and flip operations. We show that the teleportation fidelity of our proposed scheme is significantly improved compared to teleportation with no protection and a teleportation protocol based on quantum measurement reversal. Also, the explicit formula of average teleportation fidelity and success probability of the entanglement protection are derived.
Most existing quantum teleportation schemes do not consider the memory effect of noise, which is becoming increasingly serious in practical quantum communication. In this paper, we propose two quantum teleportation protocols for noisy memory channels: one based on pre-flipping (PF) and another incorporating pre-flipping with environment-assisted measurement (PF-EAM). In the PF protocol, a pre-flipping operation is applied to the entangled qubits before entanglement distribution to enhance robustness against noise. A recovery operator is then used to reverse the pre-flipping operation. In the PF-EAM protocol, environment-assisted measurement (EAM) is added to the entanglement distribution process, further improving teleportation fidelity. Since the pre-flipping operator in the two protocols is a fixed unitary operator, our protocols exclude additional parameters, which is unlike weak measurement (WM) schemes that rely on adjustable measurement strength. We derive the analytical expressions for the average fidelity and the success probability of our teleportation protocols. The results show that the pre-flipping operator in the PF protocol effectively enhances the average fidelity of quantum teleportation in a deterministic manner, while the fidelity of PF-EAM remains at constant 1, unaffected by the noise intensity in the channel. In addition, our PF-EAM achieves a higher success probability while maintaining the fidelity of 1 with respect to the existing unprotected teleportation protocol, protocol based on weak measurement and measurement reversal (WM-MR), and protocol based on quantum feed-forward control and environment-assisted measurement (QFFC-EAM) framework.
A perfect teleportation protocol requires pure maximally shared entangled states. While in reality the shared entanglement is drastically degraded due to the inevitable interaction with the noisy environment. Here, we propose a teleportation protocol to teleport an unknown qubit through amplitude damping channels with a fidelity up to one with a single copy of the entangled state. Our proposed teleportation protocol, while illustrated using the Bell and W entangled states as examples, can be utilized with any type of entangled states. In our protocol, we utilize environment-assisted measurement (EAM) during the entanglement distribution, and further modify the original teleportation protocol to apply weak measurement in the last step of teleportation. We find a balance between teleportation fidelity and success probability by varying the strength of the weak measurement. Furthermore, we investigate the protection of third-party assisted teleportation protocols, where all the qubits of the entangled state pass through the amplitude damping channel. In particular, for the third-party assisted teleportation with the W state, the decoherence of the shared entanglement can be totally suppressed by using EAM, hence no weak measurement is required to achieve an average teleportation fidelity of unity. The numerical simulation results reveal that our proposed teleportation protocol outperforms both the weak measurement based probabilistic teleportation protocol and the original teleportation protocols without protection.
This study presents an improved quantum teleportation protocol designed to enhance fidelity in noisy environments by combining weak measurements (WMs) with flip and reversal operations. In our scheme, Alice prepares a four-qubit entangled state and shares one of the entangled qubits with Bob, which serves as the quantum channel for teleporting an arbitrary single-qubit state. Since the communication channel is subject to noise, Alice performs a weak measurement on the shared qubit before transmission to reduce the impact of decoherence. Building upon existing WM-flipreversal frameworks, we propose a modified weak measurement and reversal (WMR) protocol tailored for different noises in a four-qubit entangled system. The approach applies WM and flip operations prior to transmission to enhance resilience against noise, followed by corresponding reversal operations after transmission to recover the original quantum state. We systematically compare the performance of our proposed WMR protocol with the previously proposed WM-flip-reversal method under three common noise models: amplitude damping channel (ADC), phase flip channel (PFC), and bit flip channel (BFC). Our analysis reveals that the modified WMR scheme achieves significantly higher teleportation fidelity and improved robustness, particularly in bit flip noise environments. These findings highlight the potential of optimized weak measurement strategies for developing more reliable and noise-tolerant quantum communication protocols