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

Abstract

We designed an encoding scheme, using quantum dots (QDs), for single logical qubit information by encoding quantum information onto four-photon decoherence-free states to acquire immunity against collective decoherence. The designed scheme comprised of QDs, confined in single-sided cavities (QD-cavity systems), used for arbitrary quantum information, encoded onto four-photon decoherence-free states (logical qubits). For our scheme, which can generate the four-photon decoherence-free states, and can encode quantum information onto logical qubits, high efficiency and reliable performance of the interaction between the photons and QD-cavity systems is essential. Thus, through our analysis of the performance of QD-cavity systems under vacuum noise and sideband leakage, we demonstrate that the encoding scheme for single logical qubit information could be feasibly implemented.

Procedure via cross-Kerr nonlinearities for encoding single logical qubit information onto four-photon decoherence-free states

“…Four-qubit decoherence-free state: To prevent quantum information in qubits from being affected by collective decoherence [26][27][28], logical qubits using decoherence-free subspaces [31][32][33][34][35][36][37][38][39][40][41][42] have been utilized.…”

“…In particular, utilizing a decoherence-free subspace prevents collective decoherence [26][27][28] (identical decoherence occurring in each qubit in a system) to be spread from one subspace to another subspace in a system when uncontrolled interactions between a system and environment affect the schemes of quantum information processing. Applications (passive processes) [31][32][33][34][35][36][37][38][39][40][41][42] employing a decoherence-free subspace can provide immunity against collective decoherence [26][27][28]. For the passive process, a simple method is to encode quantum information onto two-qubit systems (as a singlet state [30]) or three-qubit systems (as an entangled W state [10,12,43,44], and a three-qubit decoherence-free state [32][33][34][35]45]).…”

“…However, applications [10,12,30,[32][33][34][35][43][44][45] using two-or three-qubit systems can guarantee only a limited effect for maintaining the coherence of quantum information from the influence of collective decoherence in quantum channels. Hence, four-qubit decoherence-free subspaces (passive processes) utilizing various physical resources have been proposed to enhance the efficiency of coherent quantum information, e.g., linear optics with post-selections [35], spontaneous parametric down conversions [46,47], source of entangled state [48,49], and cavity-QED [36,37,42].…”

Procedure via cross-Kerr nonlinearities for encoding single logical qubit information onto four-photon decoherence-free states

“…In particular, utilizing a decoherence-free subspace prevents collective decoherence 32 – 36 which occurs the identical decoherence occurring in each qubit in a system to be spread from one subspace to another subspace in a system when uncontrolled interactions between a system and environment affect the schemes of quantum information processing. Applications (passive processes) 37 – 48 employing a decoherence-free subspace can provide immunity against collective decoherence 32 – 34 . For the passive process, a simple method is to encode quantum information onto two-qubit systems as a singlet state 36 or three-qubit systems as an entangled W state 12 , 14 , 49 , 50 , and a three-qubit decoherence-free state 37 – 41 , 51 .…”

“…However, applications 12 , 14 , 36 – 41 , 49 – 51 using two- or three-qubit systems can guarantee only a limited effect for maintaining the coherence of quantum information from the influence of collective decoherence in quantum channels. Hence, four-qubit decoherence-free subspaces, passive processes, utilizing various physical resources have been proposed to enhance the efficiency of coherent quantum information, e.g., linear optics with post-selections 41 , spontaneous parametric down conversions 52 , 53 , source of entangled state 54 , 55 , and cavity-QED 42 , 43 , 48 .…”