量子特性在信息领域中有着独特的功能，在提高运算速度、确保信息安全、增大信息容量和提高检测精度等方面可能突破现有经典信息系统的极限。我们以液态NMR技术实现量子信息处理中的应用主题开展研究，所取得的成果包括：1）利用NMR实验实现了两个无直接耦合自旋之间的量子密集编码和三个量子位之间的量子密集编码过程。实验结果表明：量子密集编码只需传送N-1个量子位便可以传递N个经典位的信息。2）利用NMR实验实现了三种多量子算法；提出了一种实现n阶耦合变换的理论方法，根据这种方法可实现任意量子位的Deutsch-Jozsa算法。3）提出了一种基于量子克隆的量子编码和纠错方案。该方案一方面说明了量子克隆与量子纠错存在一定程度上的联系，另一方面也反映出一些量子克隆过程本身具有一定的抗消相干的能力。4）提出用二维NMR中的多量子相干实现无消相干子空间（DFS），并在实验上验证了该DFS的避错能力。本方法有效地利用了甲基中三个磁等价的氢核，把原本需要四个化学位移各不相同的核自旋构造的二逻辑位的DFS变成了只需两个化学位移各不相同的核自旋体系构造的二逻辑位的DFS，虽然用的核自旋数“更少”，却能避免更多的错误算符。用多量子相干作为量子计算中的量子位，是一种全新的概念，可以充分利用磁等价的原子核自旋来构造多个量子位，从而扩展了可利用的量子位的数目。

This paper presents our theoretical and nuclear magnetic resonance(NMR) experimental work on several QIPs including quantum super dense coding (QSDC), quantum algorithms, quantum error correction, and decoherence-free subspace. The main contents are, 1) Using NMR technique, we realize two kinds of QSDC. The experimental results show that QSDC only needs to transfer (N-1) qubits during transmitting N bits classical information; 2) On NMR quantum computers, we realize three kinds of quantum algorithms that including four-qubit summing algorithm, four-qubit Deutsch-like algorithm and seven-qubit Deutsch-Jozsa algorithm. 3) We present a quantum error correction scheme based on quantum cloning. This scheme shows the relationship between quantum cloning and quantum error correction. 4) To avoid decoherence in quantum algorithms, we construct a decoherence-free subspace (DFS) by using multiple quantum coherences. The validity of this DFS is also experimentally verified on our NMR quantum computers. The DFS makes the three unaddressed protons in a CH3 group distinguished in two-dimensional (2D) NMR. It can protect against more error operators. This idea may provide new insights into extending the number of qubits in the sense that it effectively utilizes the magnetically equivalent nuclei.