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**From**: Janos Asboth <janos.asboth AT gmail.com>**To**: fizinfo AT lists.kfki.hu**Subject**: [Fizinfo]**Date**: Fri, 28 Mar 2014 13:17:36 +0100**Authentication-results**: mailman.kfki.hu; dkim=pass reason="2048-bit key; insecure key" header.d=gmail.com header.i= AT gmail.com header.b=dM0ac0Pp; dkim-adsp=pass; dkim-atps=neutral

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

**[Fizinfo]**,*Janos Asboth, 03/28/2014*

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