Quantum state and entanglement protection in finite temperature environment by quantum feed-forward control

We propose a quantum feed-forward control and its reversal to protect the quantum state and entanglement in a finite temperature environment. By performing weak measurement and unitary operations before decoherence, the initial state transfers to a more robust state, and after the decoherence the reversed operations are applied to recover the state. We illustrate our scheme and compare it with a scheme based on quantum gates in the case of protection from finite temperature thermal noise. The numerical results show that the performance of proposed scheme, fidelity (concurrence) in case of one-qubit (two-qubit entanglement), can be significantly improved. In addition, compared to previous control schemes, our scheme is not probabilistic and can protect the state and enhance the entanglement in presence of noise with probability one.