Fidelity Enhancement by Logical Qubit Encoding

作     者：Michael K. Henry Chandrasekhar Ramanathan Jonathan S. Hodges Colm A. Ryan Michael J. Ditty Raymond Laflamme David G. Cory 

作者机构：Department of Nuclear Science and Engineering Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Institute for Quantum Computing University of Waterloo Waterloo Ontario Canada N2L 3G1 

出 版 物：《Physical Review Letters》 (Phys Rev Lett)

年 卷 期：2007年第99卷第22期

页      面：220501-220501页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

主　　题：Quantum theory 

摘      要：We demonstrate coherent control of two logical qubits encoded in a decoherence free subspace (DFS) of four dipolar-coupled protons in an NMR quantum information processor. A pseudopure fiducial state is created in the DFS, and a unitary logical qubit entangling operator evolves the system to a logical Bell state. The four-spin molecule is partially aligned by a liquid crystal solvent, which introduces strong dipolar couplings among the spins. Although the system Hamiltonian is never fully specified, we demonstrate high fidelity control over the logical degrees of freedom. In fact, the DFS encoding leads to higher fidelity control than is available in the full four-spin Hilbert space.