ELFT HÍRADÓ

[Janos Asboth <janos.asboth AT gmail.com>]

                        MEGHÍVÓ

    Wigner FK SZFI Kvantumoptika és Kvantuminformatika Csoport szemináriuma


Pályi András
(ELTE Anyagtudományi Intézet / BME Egzotikus Kvantumfázisok):

Electrically driven spin resonance in quantum dots


abstract:

The usual way to coherently control the spin of a single electron is to use
electron spin resonance (ESR), i.e., to put the electron in a dc magnetic
field, and apply a transversal ac magnetic field pulse. Under certain
conditions, the ac magnetic field pulse can be substituted by an ac
electric field pulse: the latter couples to the charge of the electron and
thereby induces an oscillatory motion of the wave function. In turn, this
oscillatory motion results in spin Rabi oscillations, provided that a
sufficiently strong interaction between the orbital and spin degrees of
freedom (e.g., spin-orbit interaction, inhomogeneous B-field, hyperfine
interaction, etc) is present in the system.

In the talk, I will review the basic mechanisms and the experimental
state-of-the-art of electrically driven spin resonance (EDSR) in
semiconductor quantum dots. I will introduce a simple model of EDSR, in
which the coupled orbital-spin dynamics arises due to a static, but
spatially disordered magnetic field. I will describe single- and
multi-photon resonances in this model, and show that for any of these
resonances, the spin Rabi frequency is a non-monotonic function of the
amplitude of the ac electric field. Furthermore, for strong driving, the
multi-photon Rabi frequencies become comparable to the single-photon Rabi
frequency. In the context of practical quantum information processing,
these findings highlight the availability of multi-photon resonances for
qubit control with effectivity close to that of the single-photon
resonance, and the possibility that increasing the drive strength might
lead to a decreasing qubit-flip speed. I will argue that our simple model
might bear relevance for recent experiments in carbon nanotube quantum dots.

Reference: G. Szechenyi and A. Palyi, "Maximal Rabi frequency of an
electrically driven spin in a disordered magnetic field", Phys. Rev. B 89,
115409 (2014)



Az előadás helye és ideje:
Wigner FK SZFI
Konkoly-Thege M. út 29-33., 1-es épület
Tanácsterem
2014. április 1. kedd, 13:00.

Minden érdeklődőt szeretettel várunk.

Asbóth János