Creating quantum correlations between quantum-dot spins

Satoshi Sasaki, Songdan Kang, S. Miyashita +5 more

Jan A. Krzywda, Katarzyna Roszak

We study the generation of quantum correlations between two excitonic quantum dot qubits due to their interaction with the same phonon environment. Such generation results from the fact that during the pure dephasing process at finite temperatures, each exciton becomes entangled with the phonon environment. We find that for a wide range of temperatures quantum correlations are created due to the interaction. The temperature-dependence of the level of correlations created displays a trade-off type behaviour; for small temperatures the phonon-induced distrubance of the qubit states is too small to lead to a distinct change of the two-qubit state, hence, the level of created correlations is small, while for large temperatures the pure dephasing is not accompanied by the creation of entanglement between the qubits and the environment, so the environment cannot mediate qubit-qubit quantum correlations.

Vanita Srinivasa, Jacob M. Taylor, Charles Tahan

Patrik Recher, Daniel S. Saraga, Daniel Loss

We present electron spin entanglers-devices creating mobile spin-entangled electrons that are spatially separated-where the spin-entanglement in a superconductor present in form of Cooper pairs and in a single quantum dot with a spin singlet groundstate is transported to two spatially separated leads by means of a correlated two-particle tunneling event. The unwanted process of both electrons tunneling into the same lead is suppressed by strong Coulomb blockade effects caused by quantum dots, Luttinger liquid effects or by resistive outgoing leads. In this review we give a transparent description of the different setups, including discussions of the feasibility of the subsequent detection of spin-entanglement via charge noise measurements. Finally, we show that quantum dots in the spin filter regime can be used to perform Bell-type measurements that only require the measurement of zero frequency charge noise correlators.

Aymeric Delteil, Weibo Gao, Zhe Sun +1 more

Abdel‐Baset A. Mohamed, Heba Allhibi, S. S. Alharbi

This study investigates the dynamics of two-qubit correlations in a double quantum dot (QD) containing an electron and two charge-spin configurations under the influence of Rashba interaction, the Dzyaloshinsky–Moriya interaction, and an external magnetic field. The dynamics of two-qubit correlations, particularly those of local quantum Fisher information (LQFI) and local quantum uncertainty (LQU), are compared with those of log negativity. The correlation dynamics are analysed under the effects of Dzyaloshinsky–Moriya interaction, Rashba spin–orbit coupling, electron tunnelling strength, Zeeman spin-splitting coupling, and intrinsic decoherence. Importantly, in the absence of intrinsic electron QD qubit decoherence, it is found that weak couplings within the electron QD qubit system have a high capacity to create equal LQFI and LQU two-qubit correlations, as well as log-negativity entanglement. Furthermore, it is found that an increase in Zeeman spin splitting and the tunnelling effect of two electrons decreases the ability of the other couplings, DM spin–orbit and Rashba spin–orbit interactions, to generate Wigner–Yanase–Fisher correlation and entanglement, and the opposite is also true. The generation of electron-QD qubit correlations exhibits decaying oscillatory dynamics, especially when decoherence is considered. Additionally, the LQFI and LQU display different correlations, and the sudden death and birth phenomena of entanglement occur. Moreover, the phenomena of decaying oscillatory dynamics, as well as the sudden death and birth of entanglement, depend on the electron-QD-qubit couplings. These electron-QD-qubit correlations provide the quantum dot system with promising features for establishing quantum technologies.