title: Realization of a decoherence-free subspace using multiple quantum coherences.
abstract: This Letter presents a two-dimensional nuclear magnetic resonance (NMR) approach for constructing a two-logical-qubit decoherence-free subspace (DFS) by using four multiple-quantum coherences of a CH3 spin system as logical qubits. The three protons in this spin system are magnetically equivalent and can only be used as a single qubit in one-dimensional NMR. We have experimentally demonstrated that our DFS can protect against more types of decoherences than those of the one composed of four noisy physical qubits all with different chemical shifts. This idea may provide new insights into extending qubit systems in the sense that it effectively utilizes the magnetically equivalent nuclei.
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China. dxwei@sina.com.cn
authors.forename: Daxiu
authors.initials: D
authors.lastname: Wei
authors.forename: Jun
authors.initials: J
authors.lastname: Luo
authors.forename: Xianping
authors.initials: X
authors.lastname: Sun
authors.forename: Xizhi
authors.initials: X
authors.lastname: Zeng
authors.forename: Mingsheng
authors.initials: M
authors.lastname: Zhan
authors.forename: Maili
authors.initials: M
authors.lastname: Liu