Electron Fabry–Perot interferometer with two entangled magnetic impurities

Abstract

We consider a one-dimensional (1D) wire along which single conduction electrons can propagate in the presence of two spin-1/2 magnetic impurities. The electron may be scattered by each impurity via a contact-exchange interaction and thus a spin-flip generally occurs at each scattering event. Adopting a quantum waveguide theory approach, we derive the stationary states of the system at all orders in the electron-impurity exchange coupling constant. This allows us to investigate electron transmission for arbitrary initial states of the two impurity spins. We show that for suitable electron wave vectors, the triplet and singlet maximally entangled spin states of the impurities can respectively largely inhibit the electron transport or make the wire completely transparent for any electron spin state. In the latter case, a resonance condition can always be found, representing an anomalous behaviour compared to typical decoherence induced by magnetic impurities. We provide an explanation for these phenomena in terms of the Hamiltonian symmetries. Finally, a scheme to generate maximally entangled spin states of the two impurities via electron scattering is proposed.

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

“…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.…”

Manipulating quantum information with spin torque

“…The use of “flying spins” to manipulate static qubits has been discussed in the past 11 12 13 14 15 16 17 18 19 20 21 and it has been noted that the reflection matrix [ R ] in equation (2) represents a unitary transformation suitable for quantum operations if the barriers at in Fig. 1(b,c) are large enough to reflect the incident electrons completely 20 21 , which we employ in this proposal.…”

“…In this paper we will first show that (1) all standard single qubit operations can be effected without any magnetic field through interactions of the form with the itinerant or “flying” non-equilibrium spin population while (2) two qubit operations can be implemented through separate interactions of the form and with the flying spin population . The latter process has been discussed earlier by several authors 11 12 13 14 15 16 17 18 19 20 21 and we draw on this work, but there is a key distinction with the present work as explained in the next section.…”

Entanglement of magnetic impurities through electron scattering in an electric field

“…Although this asymmetry does not eliminate all the resonant effects, it restricts the constructive quantum interference [34]. It also affects the indistinguishability of the Feynmann paths of the scattered electron, decreasing the level of entanglement created [26,25]. Because our main aim is to analyse the effect of electric field and the sake of clarity, we consider the impurities initial spin state as always parallel.…”

“…with similar expression for C R , in the case when a reflected electron is detected with its spin changed. in an electron scattering process [25,41]. Is important to note that the magnitude of the spins interactions will depend on the ratio between the coupling factor J and the kinetic energy .…”