Entanglement of dynamical pairs

Charles Favre, Thomas Gauthier

Han-Xiao Zhang, Chu-Hui Fan, Jin‐Hui Wu

We study the correlated evolutions of two far-spaced Rydberg atomic pairs with different resonant frequencies, interacting via van der Waals (vdW) potentials and driven by a common laser field. They are found to exhibit in-phase (anti-phase) beating dynamics characterized by identical (complementary) intra-pair entanglements under a specific condition in regard of inter-pair vdW potentials and driving field detunings. This occurs when each atomic pair just oscillates between its ground state and symmetric entangled state because its doubly excited state and asymmetric entangled state are forbidden due to rigid dipole blockade and perfect destructive interference, respectively. More importantly, optimal inter-pair overall entanglement can be attained at each beating node corresponding to semi-optimal intra-pair entanglements, and inevitable dissipation processes just result in a slow decay of intra-pair and inter-pair entanglements yet without destroying in-phase and anti-phase beating dynamics.

Venkata Satya Surya Phaneendra Pydimarri, Timothy R Field

The dynamics of an identical pair of entangled spin-1/2 particles, both subjected to the same random magnetic field, are studied. The dynamics of the pure joint state of the pair are derived using stochastic calculus. An ensemble of such pure states is combined using the modified spin joint density matrix, and the joint relaxation time for the pair of spin-1/2 particles is obtained. The dynamics can be interpreted as a special kind of correlation involving the spatial components of the Bloch polarization vectors of the constituent entangled spin-1/2 particles.

Christian F. Roos

Leonardo A. Gonzalez Z., Riccardo Bassoli, Frank H. P. Fitzek

The distribution of entangled qubits over a noisy quantum channel and its evaluation with a quality metric as the fidelity is a key enabler of future quantum internet. We use a noisy entanglement pair generator providing pairs with dynamic fidelity. Furthermore, we model and implement the quantum channel as a rotational gate which negatively affects the distributed pair’s fidelity over time. Thus, forcing favourable and non-favourable times for the distribution of entanglement in terms of its fidelity. In this dynamic context, the entangled qubits are sequentially generated and distributed, revealing a frame with a certain number of distributed entangled pairs. A frame’s associated fidelity is fundamental to assessing the quality of the distributed pairs. It is computed by measuring a subset of the frame’s entangled pairs; therefore implying an overhead and leaving an effective payload of distributed entangled pairs. Additionally, the accuracy of the estimated frame’s fidelity depends on the amount of measured entangled pairs implying a trade-off between overhead and accuracy. In this work, we analyze the distribution of entanglement for the proposed dynamics by estimating the associated fidelity of frames with varying lengths at different operational points.

Takashi Matsuoka