Filtering and analyzing mobile qubit information via Rashba-Dresselhaus-Aharonov-Bohm interferometers

TL;DR

This paper proposes a quantum device using diamond-like loops with spin-orbit interactions and magnetic flux to filter and analyze mobile qubits, enabling tunable spin polarization and potential quantum information processing.

Contribution

It introduces a novel interferometer design that functions as an ideal spin filter and a read/write device for quantum information in electron spins.

Findings

Device achieves near-perfect spin polarization transmission.

Polarization directions are tunable independently of electron energy.

Device can also function as a spin field-effect transistor.

Abstract

Spin-1/2 electrons are scattered through one or two diamond-like loops, made of quantum dots connected by one-dimensional wires, and subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. With some symmetry between the two branches of each diamond, and with appropriate tuning of the electric and magnetic fields (or of the diamond shapes) this device completely blocks electrons with one polarization, and allows only electrons with the opposite polarization to be transmitted. The directions of these polarizations are tunable by these fields, and do not depend on the energy of the scattered electrons. For each range of fields one can tune the site and bond energies of the device so that the transmission of the fully polarized electrons is close to unity. Thus, these devices perform as ideal spin filters, and these electrons can be viewed as mobile qubits; the device writes definite quantum information on the spinors of the outgoing electrons. The device can also read the information written on incoming polarized electrons: the charge transmission through the device contains full information on this polarization. The double-diamond device can also act as a realization of the Datta-Das spin field-effect transistor.