QIC 890/891: A tutorial onNanowires in Quantum Information Processing

Daryoush Shiri, Institute for Quantum Computing (IQC)July 21, 23, 28 and 30, 2014

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Agenda• Introduction• A crash course on

• Electronic structure calculation• Phonon spectrum• Electron-phonon scattering

• Spin-Orbit Interaction• Rashba term• Dresselhaus term

• Exchange Interaction• Spin relaxation mechanisms

• Dyakonov - Perel• Elliot - Yafet• Hyperfine interaction

Daryoush Shiri, IQC 2

Introduction

Daryoush Shiri, IQC 3

• Electron spin is a natural choice for a Qubit.

• Spin of electrons in Quantum Dots (QD).

• QDs are defined by potential landscaping on 2DEG.

• 2DEG bandgap engineering in a superlattice.

Electric Field (spin-orbit interaction)

Spin to charge conversion

ESR

Nanowires & QIP

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• Semiconducting nanowires• A Host for embedding interacting Quantum Dots• Topology-based Q-Computing: Hunt for Majorana Fermions• Emitters of single photon, entangled photons

G. Weihs & H. Majedi, et al.

J. Baugh, IQC

L. Kouwenhoven, Delft

Superconducting nanowires• Detection of single photon (SNPD)

NIST

See courses offered by:Sir. Anthony Leggett and other faculty members at IQC and Physics on superconductivity

Why nanowires?

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• Compatibility with mainstream electronic chip industry

• As opposed to 2DEG based Qdot systems: Scalability of Qubits • Embedding many Qdots (spin qubits)• Better electrostatic control (potential landscape) using many gates

• Bandgap engineering

Fabrication methods

(2) Top-down methods

Group III-V (InP, InAs, InSb, GaAs, GaP, AlGaN,….)Group V (Si/Ge)Group II-VI (ZnSe/ZnTe)

(1) Bottom-up methods e.g. VLS

Review article by: J. Ramanujam, D. Shiri, and A. VermaMater. Express 1, 105-126 (2011).

Materials of Choice

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http://www.ioffe.rssi.ru/SVA/NSM/Semicond/

InAs InSb

m*/m0 = 0.023µe = 10,000 ~ 30,000 cm2/V.s @ base temp (100mK)Lande’ g-factor = 10λ MFP ~ 300nm

m*/m0 = 0.014µe = 10,000 ~ 30,000 @ base temp (100mK)Lande’ g-factor = 50

J. Baugh, IQC

InSb

Core-Shell

Tandem