Reducing quantum control for spin–spin entanglement distribution

Abstract

We present a protocol that sets maximum stationary entanglement between remote spins through scattering of mobile mediators without initialization, post-selection or feedback of the mediators' state. No time-resolved tuning is needed and, counterintuitively, the protocol generates two-qubit singlet states even when classical mediators are used. The mechanism responsible for such effect is resilient against non-optimal coupling strengths and dephasing affecting the spins. The scheme uses itinerant particles and scattering centres and can be implemented in various settings. When quantum dots and photons are used a striking result is found: injection of classical mediators, rather than quantum ones, improves the scheme efficiency.

Physical model for the generation of ideal resources in multipartite quantum networking

“…Similar conclusions can be drawn for higher-s particles [5,6]. The scheme enjoys many interesting features, such as robustness against static disorder, imperfect arrangements of RCs and phase noise [6,18].…”

“…In Refs. [6,14] it was shown that, under such working conditions, the dynamics takes place as if the static particles all occupy the same site, i.e., …”

“…Equation (2) shows that under RCs, because [Ŝ 2 ,V RC ] = 0,Ŝ 2 is a constant of motion. Here, we indicate with | − s,N the singlet state of N scattering centers of spin quantum number s. In the case of N = 2 and for an unpolarized spin state of e, it is easily checked [6,16] that the two-center singlet state | − s,2 12 is the only one such that the effective representation ofV in Eq. (2) vanishes.…”

“…The scheme enjoys many interesting features, such as robustness against static disorder, imperfect arrangements of RCs and phase noise [6,18]. Also, it does not require fine control of the interaction times or coupling strengths nor the preparation or postselection of the e's spin [6,17].…”

“…2 yields F > ∼ 0.9 already after ν = 4 iterations and regardless of N . Yet, a larger fidelity is obtained with a lower number of launches if a larger coupling strength is set [6].…”