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

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.

High-temperature Aharonov-Bohm-Casher interferometer

“…4b, Eqs. (33) and (42)]. The vector P(φ) lies in the (x, z) plane formed by two axes: the axis x, which connects contacts a and b and the axial symmetry axis of the ring (z axis perpendicular to the ring's plane).…”

Spin filtering in all-electrical three-terminal interferometers

“…The vector K αβ depends on the specific type of SOI. 16,17 Its magnitude scales with the strength of the local SOI and its direction depends on the type of SOI and on the direction of the bond αβ. Specifically, we assume that the semi-infinite leads (see Fig.…”

“…12 Indeed, several groups proposed spin filters based on a single loop connected to two terminals by single-channel 1D leads. [13][14][15][16][17] If time-reversal symmetry (TRS) is conserved in such networks and the scattering matrix of the device is unitary (meaning that the number of particles scattered at a certain energy is conserved), then the 2×2 transmission and reflection matrices (in spin space) must have degenerate eigenvalues. 18,19 As a result, all directions of the spin polarization are equally probable, and there cannot be any spin filtering.…”

“…by adding a magnetic field. [13][14][15][16][17] Alternatively, one may increase the number of terminals connected to the device and thus generate a finite spin polarization without exploiting ferromagnetic electrodes and without applying magnetic fields. Allelectrical single-loop spin filters based on three-terminal devices have been studied before; [20][21][22][23][24] in particular, Földi et al 23 demonstrated that a symmetric-ring interferometer attached to one source and two drain terminals can act as a spin beam-splitter, which polarizes the electrons in the output leads along tunable directions.…”

Transient probing of the symmetry and the asymmetry of electron interference

“…44 By properly combining it with the spin-orbit interaction, mixed actions of charge and spin interference have been shown to give rise to full spin-polarized transport. 46,47 The AB interference is also useful to affect the occupation difference between degenerate QDs 48 and modulate the current noises. 49,50 Various time-dependent aspects of DQD AB interferometers have been tackled.…”