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Title: Decoherence of two-electron spin states in quantum dots

Abstract

The time evolution of spin states of two electrons interacting with a nuclear spin bath in a quantum dot system is studied. The hyperfine interaction between the electrons and the nuclear spins is modeled by an isotropic Heisenberg interaction, and the interaction between the electron spins by Heisenberg exchange. Depending on the extent of the overlap between the spatial wave functions of the electrons, there are two physically different cases, namely, the two qubits either interact with the same set of nuclear spins or they see different nuclear spin environments. In the two cases, the decoherence of the two-qubit state is studied analytically. We have identified a class of two-qubit states that have a rich dynamics when the exchange interaction between the qubits becomes large in comparison to the hyperfine interaction strengths. The decoherence time scale is determined as a function of the bath-spin distribution and the polarizations of the initial two-qubit state. States with large decoherence times are identified by performing a minimization over all the two-qubit pure states.

Authors:
; ;  [1]
  1. Department of Physics, Indian Institute of Technology, Kanpur-208016 (India)
Publication Date:
OSTI Identifier:
20982507
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 75; Journal Issue: 5; Other Information: DOI: 10.1103/PhysRevA.75.052338; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COMPARATIVE EVALUATIONS; DISTRIBUTION; ELECTRONS; EXCHANGE INTERACTIONS; HEISENBERG MODEL; HYPERFINE STRUCTURE; MINIMIZATION; POLARIZATION; QUANTUM COMPUTERS; QUANTUM DECOHERENCE; QUANTUM DOTS; QUBITS; SIMULATION; SPIN; WAVE FUNCTIONS

Citation Formats

Rao, D. D. Bhaktavatsala, Ravishankar, V., and Subrahmanyam, V.. Decoherence of two-electron spin states in quantum dots. United States: N. p., 2007. Web. doi:10.1103/PHYSREVA.75.052338.
Rao, D. D. Bhaktavatsala, Ravishankar, V., & Subrahmanyam, V.. Decoherence of two-electron spin states in quantum dots. United States. doi:10.1103/PHYSREVA.75.052338.
Rao, D. D. Bhaktavatsala, Ravishankar, V., and Subrahmanyam, V.. Tue . "Decoherence of two-electron spin states in quantum dots". United States. doi:10.1103/PHYSREVA.75.052338.
@article{osti_20982507,
title = {Decoherence of two-electron spin states in quantum dots},
author = {Rao, D. D. Bhaktavatsala and Ravishankar, V. and Subrahmanyam, V.},
abstractNote = {The time evolution of spin states of two electrons interacting with a nuclear spin bath in a quantum dot system is studied. The hyperfine interaction between the electrons and the nuclear spins is modeled by an isotropic Heisenberg interaction, and the interaction between the electron spins by Heisenberg exchange. Depending on the extent of the overlap between the spatial wave functions of the electrons, there are two physically different cases, namely, the two qubits either interact with the same set of nuclear spins or they see different nuclear spin environments. In the two cases, the decoherence of the two-qubit state is studied analytically. We have identified a class of two-qubit states that have a rich dynamics when the exchange interaction between the qubits becomes large in comparison to the hyperfine interaction strengths. The decoherence time scale is determined as a function of the bath-spin distribution and the polarizations of the initial two-qubit state. States with large decoherence times are identified by performing a minimization over all the two-qubit pure states.},
doi = {10.1103/PHYSREVA.75.052338},
journal = {Physical Review. A},
number = 5,
volume = 75,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}