arXiv subjects

Shi-Liang Zhu

Publications and source records attributed to Shi-Liang Zhu.

At least 127 records · Page 7Linked to original sources

arXiv2011

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 different orders of braiding operations give orthogonal output states that can be distinguished through Raman spectroscopy. Realization of Majorana bound 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.

cond-mat.quant-gas↗

arXiv2010

Simulation of the spin-boson model with superconducting phase qubit coupled to a transmission line

Based on the rapid experimental developments of circuit QED, we propose a feasible scheme to simulate a spin-boson model with the superconducting circuits, which can be used to detect quantum Kosterlitz-Thouless (KT) phase transition. We design the spin-boson model by using a superconducting phase qubit coupled with a semi-infinite transmission line, which is regarded as bosonic reservoir with a continuum spectrum. By tuning the bias current or the coupling capacitance, the quantum KT transition can be directly detected through tomography measurement on the states of the phase qubit. We also estimate the experimental parameters using numerical renormalization group method.

quant-ph↗

arXiv2010

Simulating and Detecting the Quantum Spin Hall Effect in Kagomé Optical Lattice

We propose a model which includes a nearest-neighbor intrinsic spin-orbit coupling and a dimer Hamiltonian in the Kagomé lattice and promises to host the transition from the quantum spin Hall insulator to the normal insulator. In addition, we design an experimental scheme to simulate and detect this transition in the ultracold atom system. The lattice intrinsic spin-orbit coupling is generated via the laser-induced-gauge-field method. Furthermore, we establish the connection between the spin Chern number and the spin-atomic density which enables us to detect the topological quantum spin Hall insulator directly by the standard density-profile technique used in the atomic systems.

cond-mat.mes-hall↗

arXiv2010

An Experimental Proposal to Test Dynamic Quantum Non-locality with Single-Atom Interferometry

Quantum non-locality based on the well-known Bell inequality is of kinematic nature. A different type of quantum non-locality, the non-locality of the quantum equation of motion, is recently put forward with connection to the Aharonov-Bohm effect [Nature Phys. 6, 151 (2010)]. Evolution of the displacement operator provides an example to manifest such dynamic quantum non-locality. We propose an experiment using single-atom interferometry to test such dynamic quantum non-locality. We show how to measure evolution of the displacement operator with clod atoms in a spin-dependent optical lattice potential and discuss signature to identify dynamic quantum non-locality under a realistic experimental setting.

quant-ph↗

arXiv2009

Implementation of local and high-fidelity quantum conditional phase gates in a scalable two-dimensional ion trap

We propose a scheme to implement high-fidelity conditional phase gates on pair of trapped ions immersed in a two-dimensional Coulomb crystal, using interaction mediated by all axial modes without side-band addressing. We show through numerical calculations that only local modes can be excited to achieve entangling gates through shaping the laser beams, so that the complexity of the quantum gate does not increase with the size of the system. These results suggest a promising approach for realization of large scale fault-tolerant quantum computation in two dimensional traps architecture.

quant-ph↗

arXiv2009

Dark Periods in Rabi Oscillations of Superconducting Phase Qubit Coupled to a Microscopic Two-Level System

We proposed a scheme to demonstrate macroscopic quantum jumps in a superconducting phase qubit coupled to a microscopic two-level system in the Josephson tunnel junction. Irradiated with suitable microwaves, the Rabi oscillations of the qubit exhibit signatures of quantum jumps: a random telegraph signal with long intervals of intense macroscopic quantum tunneling events (bright periods) interrupted by the complete absence of tunneling events (dark periods). An analytical model was developed to describe the width of the dark periods quantitatively. The numerical simulations indicate that our analytical model captured underlying physics of the system. Besides calibrating the quality of the microscopic two-level system, our results have significance in quantum information process since dark periods in Rabi oscillations are also responsible for errors in quantum computing with superconducting qubits.

quant-ph↗

arXiv2009

Quantum computation in decoherence-free subspace with superconducting devices

We propose a scheme to implement quantum computation in decoherence-free subspace with superconducting devices inside a cavity by unconventional geometric manipulation. Universal single-qubit gates in encoded qubit can be achieved with cavity assisted interaction. A measurement-based two-qubit Controlled-Not gate is produced with parity measurements assisted by an auxiliary superconducting device and followed by prescribed single-qubit gates. The measurement of currents on two parallel devices can realize a projective measurement, which is equivalent to the parity measurement on the involved devices.

quant-ph↗

arXiv2009

Sudden death of distillability in qutrit-qutrit systems

We introduce the concept of distillability sudden death, i.e., free entangled states can evolve into non-distillable (bound entangled or separable) states in finite time under local noise. We describe the phenomenon through a specific model of local dephasing noise and compare the behavior of states in terms of the Bures fidelity. Then we propose a few methods to avoid distillability sudden death of states under (general) local dephasing noise, so that free entangled states can be robust against decoherence. Moreover, we find that bound entangled states are unstable in the limit of infinite time.

quant-ph↗

arXiv2009

Delocalization of relativistic Dirac particles in disordered one-dimensional systems and its implementation with cold atoms

We study theoretically the localization of relativistic particles in disordered one-dimensional chains. It is found that the relativistic particles tend to dislocation in comparison with the non-relativistic particles with the same disorder strength. More intriguingly, we reveal that the massless Dirac particles are entirely delocalized for any energy due to the inherent chiral symmetry, leading to a well-known result that particles are always localized in one-dimensional system for arbitrary weak disorders to break down. Furthermore, we propose a feasible scheme to simulate and detect the delocalization feature of the Dirac particles with cold atoms..

cond-mat.dis-nn↗

arXiv2009

Implementing topological quantum manipulation with superconducting circuits

A two-component fermion model with conventional two-body interactions was recently shown to have anyonic excitations. We here propose a scheme to physically implement this model by transforming each chain of two two-component fermions to the two capacitively coupled chains of superconducting devices. In particular, we elaborate how to achieve the wanted operations to create and manipulate the topological quantum states, providing an experimentally feasible scenario to access the topological memory and to build the anyonic interferometry.

quant-ph↗

arXiv2009

Implementing Genuine Multi-Qubit Entanglement of Two-Level-System Inside a Superconducting Phase Qubit

The interaction between a superconducting phase qubit and the two-level systems locating inside the Josephson tunnel barrier is shown to be described by the XY model, which is naturally used to implement the iSWAP gate. With this gate, we propose a scheme to efficiently generate genuine multi-qubit entangled states of such two-level systems, including multipartite W state and cluster states. In particularly, we show that, with the help of the phase qubit, the entanglement witness can be used to efficiently detect the produced genuine multi-qubit entangled states. Furthermore, we analyze that the proposed approach for generating multi-qubit entangled states can be used in a wide class of candidates for quantum computation.

quant-ph↗

arXiv2009

Realizing and Detecting the Haldane's Quantum Hall effect with Ultracold Atoms

We design an ingenious scheme to realize the Haldane's quantum Hall model without Landau level by using ultracold atoms trapped in an optical lattice. Three standing-wave laser beams are used to construct a wanted honeycomb lattice, where different on-site energies in two sublattices required in the Haldane's model can be implemented through tuning the phase of one of the laser beams. The staggered magnetic field is generated from the Berry phase associated with the atom moving in a region with other three standing-wave laser beams. Moreover, we establish a relation between the Hall conductivity and the equilibrium atomic density upon turning on a stimulated uniform magnetic field, which enables us to detect the topological Chern number with the density profile measurement technique that is typically used in ultracold atoms experiments.

cond-mat.mes-hall↗

arXiv2008

A scheme for generating entangled cluster state of atomic ensembles

It was shown in Ref.[Phys.Rev.A 77,045802(2008)] that the dynamics of a control atom and an atomic sample interacting dispersively with a cavity can be discribed by the Jaynes-Cummings model and the collective mode of the atomic sample can be analogous with a bosonic mode. Here, by analogizing the behaviour of the atomic sample with the one of the cavity, we propose a scheme to generate cluster states of atomic ensembles by Cavity QED.

quant-ph↗

arXiv2008

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.

quant-ph↗

arXiv2008

Geometric phases and quantum phase transitions

Quantum phase transition is one of the main interests in the field of condensed matter physics, while geometric phase is a fundamental concept and has attracted considerable interest in the field of quantum mechanics. However, no relevant relation was recognized before recent work. In this paper, we present a review of the connection recently established between these two interesting fields: investigations in the geometric phase of the many-body systems have revealed so-called "criticality of geometric phase", in which geometric phase associated with the many-body ground state exhibits universality, or scaling behavior in the vicinity of the critical point. In addition, we address the recent advances on the connection of some other geometric quantities and quantum phase transitions. The closed relation recently recognized between quantum phase transitions and some of geometric quantities may open attractive avenues and fruitful dialog between different scientific communities.

quant-ph↗

arXiv2008

Physical implementation of topologically decoherence-protected superconducting qubits

We propose a scenario to physically implement a kind of topologically decoherence-protected qubit using superconducting devices coupled to a micro-wave cavity mode with unconventional geometric operations. It is shown that the two needed interactions for selective devices, which are required for implementing such protected qubits, as well as single-qubit gates, can be achieved by using the external magnetic flux. The easy combination of individual addressing with the many-device setup proposed in the system presents a distinct merit in comparison with the implementation of topologically protected qubits in a trapped-ion system.

quant-ph↗

arXiv2007

Detecting unambiguously non-Abelian geometric phases with trapped ions

We propose for the first time an experimentally feasible scheme to disclose the noncommutative effects induced by a light-induced non-Abelian gauge structure with trapped ions. Under an appropriate configuration, a true non-Abelian gauge potential naturally arises in connection with the geometric phase associated with two degenerated dark states in a four-state atomic system interacting with three pulsed laser fields. We show that the population in atomic state at the end of a composed path formed by two closed loops $C_1$ and $C_2$ in the parameter space can be significantly different from the composed counter-ordered path. This population difference is directly induced by the noncommutative feature of non-Abelian geometric phases and can be detected unambiguously with current technology.

quant-ph↗

arXiv2007

Simulation and detection of Dirac fermions with cold atoms in an optical lattice

We propose an experimental scheme to simulate and observe relativistic Dirac fermions with cold atoms in a hexagonal optical lattice. By controlling the lattice anisotropy, one can realize both massive and massless Dirac fermions and observe the phase transition between them. Through explicit calculations, we show that both the Bragg spectroscopy and the atomic density profile in a trap can be used to demonstrate the Dirac fermions and the associated phase transition.

cond-mat.mtrl-sci↗