The experimental scheme for protecting quantum entanglement via Hadamard and CNOT gates

<p><strong>Figure 7.</strong> The experimental scheme for protecting quantum entanglement via Hadamard and CNOT gates. The experimental setup includes four parts: entangled state generation, state preparation, amplitude damping and recovering operations. Notations: HWP—half-wave plate, QWP—quarter-wave plate, PBS—polarization beam splitter, CKerr—cross-Kerr medium, SKerr—self-Kerr medium, DA—detector on ancilla qubit, DS—detector on system qubit, HWPC—half-wave plate for compensation, P—polarizer.</p> <p><strong>Abstract</strong></p> <p>Quantum entanglement is a critical resource for quantum information and quantum computation. However, entanglement of a quantum system is subjected to change due to the interaction with the environment. One typical result of the interaction is the amplitude damping that usually results in the reduction of the entanglement. Here we propose a protocol to protect quantum entanglement from the amplitude damping by applying Hadamard and CNOT gates. As opposed to some recently studied methods, the scheme presented here does not require weak measurement in the reversal process, leading to a faster recovery of entanglement. We propose a possible experimental implementation based on linear optical system.