Use of quadrupolar nuclei for quantum-information processing by nuclear magnetic resonance: Implementation of a quantum algorithm

Ranabir Das and Anil Kumar
Phys. Rev. A 68, 032304 – Published 10 September 2003
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Abstract

Physical implementation of quantum-information processing by liquid-state nuclear magnetic resonance, using weakly coupled spin-12 nuclei of a molecule, is well established. Nuclei with spin>1/2 oriented in liquid-crystalline matrices is another possibility. Such systems have multiple qubits per nuclei and large quadrupolar couplings resulting in well separated lines in the spectrum. So far, creation of pseudopure states and logic gates has been demonstrated in such systems using transition selective radio-frequency pulses. In this paper we report two developments. First, we implement a quantum algorithm that needs coherent superposition of states. Second, we use evolution under quadrupolar coupling to implement multiqubit gates. We implement the Deutsch-Jozsa algorithm on a spin-32 (2 qubit) system. The controlled-NOT operation needed to implement this algorithm has been implemented here by evolution under the quadrupolar Hamiltonian. To the best of our knowledge, this method has been implemented for the first time in quadrupolar systems. Since the quadrupolar coupling is several orders of magnitude greater than the coupling in weakly coupled spin-12 nuclei, the gate time decreases, increasing the clock speed of the quantum computer.

  • Received 26 December 2002

DOI:https://doi.org/10.1103/PhysRevA.68.032304

©2003 American Physical Society

Authors & Affiliations

Ranabir Das1 and Anil Kumar1,2

  • 1Department of Physics, Indian Institute of Science, Bangalore 560012, India
  • 2Sophisticated Instruments Facility, Indian Institute of Science, Bangalore 560012, India

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Vol. 68, Iss. 3 — September 2003

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