Generation of hybrid four-qubit entangled decoherence-free states assisted by the cavity-QED system

Encoding scheme using quantum dots for single logical qubit information onto four-photon decoherence-free states

“…In various quantum information processing schemes, quantum entanglement (main resource) can be easily attenuated by the influence of the environment-system. To solve this issue, the concept of a decoherencefree subspace [32][33][34][35][43][44][45][50][51][52][59][60][61] has been widely employed in quantum communications [86][87][88][89] and quantum computations [90][91][92] for robustness against collective decoherence [32][33][34] . In this paper, we proposed the encoding scheme, which consisted of the generation of four-photon decoherence-free states, and the encoding process to encode arbitrary quantum information onto logical qubits, using QD-cavity systems for single logical qubit information.…”

“…This means that the reliable performance of all procedures depend on the source of entangled state in spite of utilizing linearly optical device with ease. Also, in the previous schemes using cavity-QED 44 , 51 or XKNLs 52 , 53 , these works ignored the vacuum noise in QD dipole operation and sideband leakage in cavity mode 44 , 51 , and the decoherence effect in nonlinearly optical gate 52 , 53 .…”

“…Thus, the applications of a four-qubit decoherence-free subspace have been designed for increasing the maintenance of coherent quantum information. For the generations of four-qubit decoherence-free state, many researchers have exploited various resources, such as spontaneous parametric down conversions (SPDC) 46 , 47 or source of entangled state 48 , 49 with linear optics, Zeno-like measurements and post-selections 50 , cavity-QED 44 , 51 , and cross-Kerr nonlinearities (XKNLs) 52 , 53 .…”

“…However, for the efficient protection of quantum information, the minimum requirement for the decoherence-free subsystem is the dimension of the above two-qubit physical system. Thus, many schemes, which are capable of encoding quantum information onto three-qubit systems, have been proposed, such as the entangled W state [36][37][38][39][40][41][42] and three-qubit decoherence-free state 21,22,[43][44][45][46] . But, utilizations of two-qubit 35 or three-qubit 21,22,[43][44][45][46] can also provide only minimal effect for the preservation of quantum information under the affections of noise in quantum channel.…”

“…For robust quantum information processing against collective decoherence, due to uncontrolled coupling between a system and the environment, the utilization of logical qubits {|0 L �, |1 L �} based on a decoherence-free subspace has been proposed [32][33][34] . Thus, one of the proposed concepts [32][33][34][35][43][44][45][50][51][52][59][60][61] for logical qubits is the design of four-qubit decoherence-free states 44,[50][51][52] , as follows:…”