Effect of randomness on quantum data buses of Heisenberg spin chains

Sangchul Oh, Yun Pil Shim, Jianjia Fei, Mark Friesen, Xuedong Hu

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

A strongly coupled spin chain can mediate long-distance effective couplings or entanglement between remote qubits and can be used as a quantum data bus. We study how the fidelity of a spin-1/2 Heisenberg chain as a spin bus is affected by static random exchange couplings and magnetic fields. We find that, while nonuniform exchange couplings preserve the isotropy of the qubit effective couplings, they cause the energy levels, the eigenstates, and the magnitude of the couplings to vary locally. On the other hand, random local magnetic fields lead to an avoided level crossing for the bus ground-state manifold and cause the effective qubit couplings to be anisotropic. Interestingly, the total magnetic moment of the ground state of an odd-size bus may not be parallel to the average magnetic field. Its alignment depends on both the direction of the average field and the field distribution, in contrast with the ground state of a single spin which always aligns with the applied magnetic field to minimize the Zeeman energy. Lastly, we calculate sensitivities of the spin bus to such local variations, which are potentially useful for evaluating decoherence when dynamical fluctuations in the exchange coupling or magnetic field are considered.

Original languageEnglish
Article number224418
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume85
Issue number22
DOIs
Publication statusPublished - 15 Jun 2012
Externally publishedYes

Fingerprint

Exchange coupling
Magnetic fields
Ground state
magnetic fields
ground state
Magnetic moments
Electron energy levels
causes
isotropy
eigenvectors
magnetic moments
energy levels
alignment
sensitivity
energy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Effect of randomness on quantum data buses of Heisenberg spin chains. / Oh, Sangchul; Shim, Yun Pil; Fei, Jianjia; Friesen, Mark; Hu, Xuedong.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 85, No. 22, 224418, 15.06.2012.

Research output: Contribution to journalArticle

Oh, Sangchul ; Shim, Yun Pil ; Fei, Jianjia ; Friesen, Mark ; Hu, Xuedong. / Effect of randomness on quantum data buses of Heisenberg spin chains. In: Physical Review B - Condensed Matter and Materials Physics. 2012 ; Vol. 85, No. 22.
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