Shi-Liang Zhu

Probing Non-Abelian Statistics of Majorana Fermions in Ultracold Atomic Superfluid

We propose an experiment to directly probe the non-abelian statistics of Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms. We show that different orders of braiding operations give orthogonal output states that can be distinguished through Raman spectroscopy. Realization of Majorana states in an s-wave superfluid requires strong spin-orbital coupling and a controllable Zeeman field in the perpendicular direction. We present a simple laser configuration to generate the artificial spin-orbital coupling and the required Zeeman field in the dark-state subspace.

Realizing and detecting the quantum Hall effect without landau levels by using ultracold atoms.

L. B. Shao, Shi-Liang Zhu1,∗ L. Sheng, D. Y. Xing, and Z. D. Wang Institute for Condensed Matter Physics and Department of Physics, South China Normal University, Guangzhou, China National Laboratory of Solid State Microstructure and Department of Physics, Nanjing University, Nanjing, China Department of Physics and Center of Theoretical and Computational Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China

Experimental realization of stimulated Raman shortcut-to-adiabatic passage with cold atoms

Accurate control of a quantum system is a fundamental requirement in many areas of modern science ranging from quantum information processing to high-precision measurements. A significantly important goal in quantum control is preparing a desired state as fast as possible, with sufficiently high fidelity allowed by available resources and experimental constraints. Stimulated Raman adiabatic passage (STIRAP) is a robust way to realize high-fidelity state transfer but it requires a sufficiently long operation time to satisfy the adiabatic criteria. Here we theoretically propose and then experimentally demonstrate a shortcut-to-adiabatic protocol to speed-up the STIRAP. By modifying the shapes of the Raman pulses, we experimentally realize a fast and high-fidelity stimulated Raman shortcut-to-adiabatic passage that is robust against control parameter variations. The all-optical, robust and fast protocol demonstrated here provides an efficient and practical way to control quantum systems.

Relativistic quantum effects of Dirac particles simulated by ultracold atoms

Quantum simulation is a powerful tool to study a variety of problems in physics, ranging from high-energy physics to condensed-matter physics. In this article, we review the recent theoretical and experimental progress in quantum simulation of Dirac equation with tunable parameters by using ultracold neutral atoms trapped in optical lattices or subject to light-induced synthetic gauge fields. The effective theories for the quasiparticles become relativistic under certain conditions in these systems, making them ideal platforms for studying the exotic relativistic effects. We focus on the realization of one, two, and three dimensional Dirac equations as well as the detection of some relativistic effects, including particularly the well-known Zitterbewegung effect and Klein tunneling. The realization of quantum anomalous Hall effects is also briefly discussed.

Quantum jumps between macroscopic quantum states of a superconducting qubit coupled to a microscopic two-level system.

We report the observation of quantum jumps between macroscopic quantum states in a superconducting phase qubit coupled to the two-level systems in the Josephson tunnel junction, and all key features of quantum jumps are confirmed in the experiments. Moreover, quantum jumps can be used to calibrate such two-level systems, which are believed to be one of the main decoherence sources in Josephson devices.

Josephson dynamics of a spin-orbit-coupled Bose-Einstein condensate in a double-well potential

We investigate the quantum dynamics of an experimentally realized spin-orbit coupled Bose-Einstein condensate in a double well potential. The spin-orbit coupling can significantly enhance the atomic inter-well tunneling. We find the coexistence of internal and external Josephson effects in the system, which are moreover inherently coupled in a complicated form even in the absence of interatomic interactions. Moreover, we show that the spin-dependent tunneling between two wells can induce a net atomic spin current referred as spin Josephson effects. Such novel spin Josephson effects can be observable for realistically experimental conditions.

Growth of LiNbO3 optical waveguide films by excimer laser ablation

Abstract Waveguiding LiNbO 3 films were prepared on sapphire substrates by excimer laser ablation. The as-grown films were characterized by XRD and SEM techniques, which revealed that epitaxial c -oriented and a -oriented LiNbO 3 films were achieved on (001) and (012) sapphire substrates, respectively. The optical waveguiding properties were demonstrated by measuring the TM and TE modes.

High fidelity quantum state transfer in electromechanical systems with intermediate coupling.

Hybrid quantum systems usually consist of two or more subsystems, which may take the advantages of the different systems. Recently, the hybrid system consisting of circuit electromechanical subsystems have attracted great attention due to its advanced fabrication and scalable integrated photonic circuit techniques. Here, we propose a scheme for high fidelity quantum state transfer between a superconducting qubit and a nitrogen-vacancy center in diamond, which are coupled to a superconducting transmission-line resonator with coupling strength g1 and a nanomechanical resonator with coupling strength g2, respectively. Meanwhile, the two resonators are parametrically coupled with coupling strength J. The system dynamics, including the decoherence effects, is numerical investigated. It is found that both the small () and large () coupling regimes of this hybrid system can not support high fidelity quantum state transfer before significant technique advances. However, in the intermediate coupling regime (J ~ g1 ~ g2), in contrast to a conventional wisdom, high fidelity quantum information transfer can be implemented, providing a promising route towards high fidelity quantum state transfer in similar coupled resonators systems.

Simulating and exploring Weyl semimetal physics with cold atoms in a two-dimensional optical lattice

Synergetic Innovation Center of Quantum Information and Quantum Physics,University of Science and Technology of China, Hefei 230026, China(Dated: April 30, 2015)We propose a scheme to simulate and explore Weyl semimetal physics with ultracold fermionicatoms in a two-dimensional square optical lattice subjected to experimentally realizable spin-orbitcoupling and an artificial dimension from an external parameter space, which may increase experi-mental feasibility compared with the cases in three-dimensional optical lattices. It is shown that thissystem with a tight-binding model is able to describe essentially three-dimensional Weyl semimetalswith tunable Weyl points. The relevant topological properties are also addressed by means of theChern number and the gapless edge states. Furthermore, we illustrate that the mimicked Weylpoints can be experimentally detected by measuring the atomic transfer fractions in a Bloch-Zeneroscillation, and the characteristic topological invariant can be measured with the particle pumpingapproach.

Demonstration of Geometric Landau-Zener Interferometry in a Superconducting Qubit

Geometric quantum manipulation and Landau-Zener interferometry have been separately explored in many quantum systems. In this Letter, we combine these two approaches to study the dynamics of a superconducting phase qubit. We experimentally demonstrate Landau-Zener interferometry based on the pure geometric phases in this solid-state qubit. We observe the interference caused by a pure geometric phase accumulated in the evolution between two consecutive Landau-Zener transitions, while the dynamical phase is canceled out by a spin-echo pulse. The full controllability of the qubit state as a function of the intrinsically robust geometric phase provides a promising approach for quantum state manipulation.