Observation of Fast Evolution in Parity-Time-Symmetric System

To find and realize the optimal evolution between two states is significant both in theory and application. In quantum mechanics, the minimal evolution is bounded by the gap between the largest and smallest eigenvalue of the Hamiltonian. In the parity-time-symmetric(PT-symmetric) Hamiltonian theory, it was predicted that the optimized evolution time can be reduced drastically comparing to the bound in the Hermitian case, and can become even zero. In this Letter, we report the experimental observation of the fast evolution of a PT-symmetric Hamiltonian in an nuclear magnetic resonance (NMR) quantum system. The experimental results demonstrate that the PT-symmetric Hamiltonian can indeed evolve much faster than that in a quantum system, and time it takes can be arbitrary close to zero.Comment: 13 pages, 5 figure

Pure States Tomography with Fourier Transformation

Quantum computer is showing its dramatic potential in nowadays information processing. However, by the rule of quantum mechanics, the output state of a quantum computer could be a general superposed quantum state, which can not be directly readout as the output of a classical computer. In this paper, we construct minimal measurement resources for uniquely determination of $N$-qubit pure state. Two adaptive protocols are proposed and the quantum circuits for each protocol are depicted. Additionally, the experiments on IBM 5-qubit quantum computer, as well as the numerical investigations demonstrate their feasibility.Comment: 8 pages+10 figures. All comments welcome

A survey of universal quantum von Neumann architecture

The existence of universal quantum computers has been theoretically well established. However, building up a real quantum computer system not only relies on the theory of universality, but also needs methods to satisfy requirements on other features, such as programmability, modularity, scalability, etc. To this end, we study the recently proposed model of quantum von Neumann architecture, by putting it in a practical and broader setting, namely, the hierarchical design of a computer system. We analyze the structures of quantum CPU and quantum control unit, and draw their connections with computational advantages. We also point out that a recent demonstration of our model would require less than 20 qubits.Comment: Special Issue Editorial Board Members' Collection Series on Quantum Entanglemen