Zhen-Biao Yang

Bio: Zhen-Biao Yang is an academic researcher from Fuzhou University. The author has contributed to research in topics: Quantum entanglement & Qubit. The author has an hindex of 16, co-authored 101 publications receiving 1000 citations. Previous affiliations of Zhen-Biao Yang include Yale University & University of Science and Technology of China.

Holonomic Quantum Control with Continuous Variable Systems

Abstract: Universal computation of a quantum system consisting of superpositions of well-separated coherent states of multiple harmonic oscillators can be achieved by three families of adiabatic holonomic gates. The first gate consists of moving a coherent state around a closed path in phase space, resulting in a relative Berry phase between that state and the other states. The second gate consists of ``colliding'' two coherent states of the same oscillator, resulting in coherent population transfer between them. The third gate is an effective controlled-phase gate on coherent states of two different oscillators. Such gates should be realizable via reservoir engineering of systems that support tunable nonlinearities, such as trapped ions and circuit QED.

Quantum phase gates for two atoms trapped in separate cavities within the null- and single-excitation subspaces

Abstract: We propose a scheme for realizing quantum phase gates for two atoms trapped in separate cavities connected by an optical fiber. In the scheme, the atoms, cavities, and fiber mode are in resonance. In contrast to the original scheme [A. Serafini, S. Mancini, and S. Bose, Phys. Rev. Lett. 96, 010503 (2006)], the gates are performed within the null- and single-excitation subspaces in virtue of the asymmetric encoding for two atomic qubits and can function beyond the limit that the atom-cavity coupling is much smaller than the cavity-fiber coupling. We study the stability of the gates and the influences of dissipation and show that such gates are robust.

Implementation of a multiqubit quantum phase gate in a neutral atomic ensemble via the asymmetric Rydberg blockade

Abstract: We report a scheme for implementing a multiqubit quantum phase gate in a neutral atomic ensemble via an asymmetric Rydberg blockade. The multiqubit gate is successfully realized by following a three-step approach. The neutral-atom qubits are always illuminated by the common laser beams and therefore individual addressing of the atoms is not required. The gate errors induced by atomic spontaneous emission, imperfect excitation blockade, and atomic motion are discussed.

Demonstration of Controlled-Phase Gates between Two Error-Correctable Photonic Qubits.

Abstract: To realize fault-tolerant quantum computing, it is necessary to store quantum information in logical qubits with error correction functions, realized by distributing a logical state among multiple physical qubits or by encoding it in the Hilbert space of a high-dimensional system. Quantum gate operations between these error-correctable logical qubits, which are essential for implementation of any practical quantum computational task, have not been experimentally demonstrated yet. Here we demonstrate a geometric method for realizing controlled-phase gates between two logical qubits encoded in photonic fields stored in cavities. The gates are realized by dispersively coupling an ancillary superconducting qubit to these cavities and driving it to make a cyclic evolution depending on the joint photonic state of the cavities, which produces a conditional geometric phase. We first realize phase gates for photonic qubits with the logical basis states encoded in two quasiorthogonal coherent states, which have important implications for continuous-variable-based quantum computation. Then we use this geometric method to implement a controlled-phase gate between two binomially encoded logical qubits, which have an error-correctable function.

Steady-State Entanglement for Distant Atoms by Dissipation in Coupled Cavities

Abstract: We propose a scheme for the generation of entangled states for two atoms trapped in separate cavities coupled to each other. The scheme is based on the competition between the unitary dynamics induced by the classical fields and the collective decays induced by the dissipation of two delocalized field modes. Under certain conditions, the symmetric or asymmetric entangled state is produced in the steady state. The analytical result shows that the distributed steady entanglement can be achieved with high fidelity independent of the initial state and is robust against parameter fluctuations. We also find out that the linear scaling of entanglement fidelity has a quadratic improvement compared to distributed entangled state preparation protocols based on unitary dynamics.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate*

Abstract: Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

Generation of Non-classical Motional States of a Trapped Atom

Abstract: We report the creation of thermal, Fock, coherent, and squeezed states of motion of a harmonically bound {sup 9}Be{sup +} ion. The last three states are coherently prepared from an ion which has been initially laser cooled to the zero point of motion. The ion is trapped in the regime where the coupling between its motional and internal states, due to applied (classical) radiation, can be described by a Jaynes-Cummings-type interaction. With this coupling, the evolution of the internal atomic state provides a signature of the number state distribution of the motion. {copyright} {ital 1996 The American Physical Society.}