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Chui-ping Yang - One of the best experts on this subject based on the ideXlab platform.

  • implementing a multi target qubit controlled not Gate with logical qubits outside a decoherence free subspace and its application in creating quantum entangled states
    Physical Review A, 2020
    Co-Authors: Chui-ping Yang, Yu Zhang, Franco Nori
    Abstract:

    In general, implementing a multi-logical-qubit Gate by manipulating quantum states in a decoherence-free subspace (DFS) becomes more complex and difficult when increasing the number of logical qubits. In this work, we propose an idea to realize quantum Gates by manipulating quantum states outside their DFS but having the states of the logical qubits remain in their DFS before and after the Gate Operation. This proposal has the following features: (i) because the states are manipulated outside the DFS, the multiqubit Gate implementation can be simplified when compared to realizing a multiqubit Gate via manipulating quantum states within the DFS, which usually requires unitary Operations over a large DFS, and (ii) because the states of the logical qubits return to the DFS after the Gate Operation, the errors caused by decoherence during the Gate Operation are not accumulated for a long-running calculation, and the states of the logical qubits are immune to decoherence when they are stored. Based on this proposal, we then present a way for realizing a multi-target-qubit controlled-not Gate using logical qubits encoded in a decoherence-free subspace against collective dephasing. This Gate is realized by employing qutrits (three-level quantum systems) placed in a cavity or coupled to a resonator. This proposal has the following advantages: (i) the states of the logical qubits return to their DFS after the Gate Operation; (ii) the Gate can be implemented with only a few basic Operations; (iii) the Gate Operation time is independent of the number of logical qubits; (iv) this Gate can be deterministically implemented because no measurement is needed; (v) the intermediate higher-energy level for all qutrits is not occupied during the entire Operation, thus decoherence from this level is greatly suppressed; (vi) this proposal is universal and can be applied to realize the proposed Gate using natural atoms or artificial atoms (e.g., quantum dots, nitrogen-vacancy centers, and various superconducting qutrits, etc.) placed in a cavity or coupled to a resonator. As an application, we also show how to apply this Gate to create a Greenberger-Horne-Zeilinger (GHZ) entangled state of multiple logical qubits encoded in DFS, and further investiGate the experimental feasibility for creating the GHZ state of three logical qubits in the DFS, by using six superconducting transmon qutrits coupled to a one-dimensional coplanar waveguide resonator.

  • circuit qed single step realization of a multiqubit controlled phase Gate with one microwave photonic qubit simultaneously controlling n 1 microwave photonic qubits
    arXiv: Quantum Physics, 2019
    Co-Authors: Zhenfei Zheng, Yu Zhang, Chui-ping Yang
    Abstract:

    We present a novel method to realize a multi-target-qubit controlled phase Gate with one microwave photonic qubit simultaneously controlling $n-1$ target microwave photonic qubits. This Gate is implemented with $n$ microwave cavities coupled to a superconducting flux qutrit. Each cavity hosts a microwave photonic qubit, whose two logic states are represented by the vacuum state and the single photon state of a single cavity mode, respectively. During the Gate Operation, the qutrit remains in the ground state and thus decoherence from the qutrit is greatly suppressed. This proposal requires only a single-step Operation and thus the Gate implementation is quite simple. The Gate Operation time is independent of the number of the qubits. In addition, this proposal does not need applying classical pulse or any measurement. Numerical simulations demonstrate that high-fidelity realization of a controlled phase Gate with one microwave photonic qubit simultaneously controlling two target microwave photonic qubits is feasible with current circuit QED technology. The proposal is quite general and can be applied to implement the proposed Gate in a wide range of physical systems, such as multiple microwave or optical cavities coupled to a natural or artificial $\Lambda$-type three-level atom.

  • single step implementation of a multiple target qubit controlled phase Gate without need of classical pulses
    Optics Letters, 2014
    Co-Authors: Chui-ping Yang, Fengyang Zhang, Shi-biao Zheng
    Abstract:

    We propose a simple method for achieving a multiqubit phase Gate of one qubit simultaneously controlling n target qubits, by using three-level quantum systems (i.e., qutrits) coupled to a cavity or resonator. The Gate can be realized via one Operational step, without need of classical pulses, and by a virtual photon process. Thus, the Gate Operation is greatly simplified and decoherence from the cavity decay is much reduced, when compared with previous proposals. In addition, the Operation time is independent of the number of qubits and no adjustment of the qutrit level spacings or the cavity frequency is needed during the Operation.

  • single step implementation of a multiple target qubit controlled phase Gate without need of classical pulses
    arXiv: Quantum Physics, 2014
    Co-Authors: Chui-ping Yang, Fengyang Zhang, Shi-biao Zheng
    Abstract:

    We propose a simple method for realizing a multiqubit phase Gate of one qubit simultaneously controlling $n$ target qubits, by using three-level quantum systems (i.e., qutrits) coupled to a cavity or resonator. The Gate can be implemented using one Operational step and without need of classical pulses, and no photon is populated during the Operation. Thus, the Gate Operation is greatly simplified and decoherence from the cavity decay is much reduced, when compared with the previous proposals. In addition, the Operation time is independent of the number of qubits and no adjustment of the qutrit level spacings or the cavity frequency is needed during the Operation.

  • realizing an n target qubit controlled phase Gate in cavity qed an approach without classical pulses
    arXiv: Quantum Physics, 2012
    Co-Authors: Man Liu, Chui-ping Yang
    Abstract:

    We propose a way to realize a multiqubit controlled phase Gate with one qubit simultaneously controlling $n$ target qubits using atoms in cavity QED. In this proposal, there is no need of using classical pulses during the entire Gate Operation. The Gate Operation time scales as $\sqrt{n}$ only and thus the Gate can be performed faster when compared with sending atoms through the cavity one at a time. In addition, only three steps of Operations are required for realizing this $n$-target-qubit controlled phase Gate. This proposal is quite general, which can be applied to other physical systems such as various superconducting qubits coupled to a resonator, NV centers coupled to a microsphere cavity or quantum dots in cavity QED.

Mansun Chan - One of the best experts on this subject based on the ideXlab platform.

Shi-biao Zheng - One of the best experts on this subject based on the ideXlab platform.

  • single step implementation of a multiple target qubit controlled phase Gate without need of classical pulses
    Optics Letters, 2014
    Co-Authors: Chui-ping Yang, Fengyang Zhang, Shi-biao Zheng
    Abstract:

    We propose a simple method for achieving a multiqubit phase Gate of one qubit simultaneously controlling n target qubits, by using three-level quantum systems (i.e., qutrits) coupled to a cavity or resonator. The Gate can be realized via one Operational step, without need of classical pulses, and by a virtual photon process. Thus, the Gate Operation is greatly simplified and decoherence from the cavity decay is much reduced, when compared with previous proposals. In addition, the Operation time is independent of the number of qubits and no adjustment of the qutrit level spacings or the cavity frequency is needed during the Operation.

  • single step implementation of a multiple target qubit controlled phase Gate without need of classical pulses
    arXiv: Quantum Physics, 2014
    Co-Authors: Chui-ping Yang, Fengyang Zhang, Shi-biao Zheng
    Abstract:

    We propose a simple method for realizing a multiqubit phase Gate of one qubit simultaneously controlling $n$ target qubits, by using three-level quantum systems (i.e., qutrits) coupled to a cavity or resonator. The Gate can be implemented using one Operational step and without need of classical pulses, and no photon is populated during the Operation. Thus, the Gate Operation is greatly simplified and decoherence from the cavity decay is much reduced, when compared with the previous proposals. In addition, the Operation time is independent of the number of qubits and no adjustment of the qutrit level spacings or the cavity frequency is needed during the Operation.

  • virtual photon induced quantum phase Gates for two distant atoms trapped in separate cavities
    arXiv: Quantum Physics, 2012
    Co-Authors: Shi-biao Zheng
    Abstract:

    We propose a scheme for implementing quantum Gates for two atoms trapped in distant cavities connected by an optical fiber. The effective long-distance coupling between the two distributed qubits is achieved without excitation and transportation of photons through the optical fiber. Since the cavity modes and fiber mode are never populated and the atoms undergo no transitions, the Gate Operation is insensitive to the decoherence effect when the thermal photons in the environment are negligible. The scheme opens promising perspectives for networking quantum information processors and implementing distributed and scalable quantum computation.

Jin He - One of the best experts on this subject based on the ideXlab platform.

  • generic carrier based core model for undoped four terminal double Gate mosfets valid for symmetric asymmetric and independent Gate Operation modes
    IEEE Transactions on Electron Devices, 2008
    Co-Authors: Jin He, Yue Fu, Jinhua Hu, Wei Bian, Yan Song, Xing Zhang, Mansun Chan
    Abstract:

    A generic carrier-based core model for undoped four-terminal double-Gate (DG) MOSFETs has been developed and is presented in this paper. The model is valid for symmetric, asymmetric, and independent-Gate-Operation modes. Based on the exact solution of the 1-D Poisson's equation in a general DG MOSFET configuration, a rigorous derivation of the drain-current equations from the Pao-Sah's double integral has been performed. By using the channel carriers as the intermediate variable, a very compact analytical drain-current expression can be obtained. The model is extensively verified by comparisons with a 2-D numerical simulator under a large number of biasing conditions. The concise mathematical formulation allows the unification of various DG models into a carrier-based core model for a compact DG MOSFET model development.

Shou Zhang - One of the best experts on this subject based on the ideXlab platform.

  • one step implementation of a multiqubit phase Gate with one control qubit and multiple target qubits in coupled cavities
    Optics Letters, 2014
    Co-Authors: Hong-fu Wang, Aidong Zhu, Shou Zhang
    Abstract:

    We propose a one-step scheme to implement a multiqubit controlled phase Gate with one qubit simultaneously controlling multiple qubits with three-level atoms at distant nodes in coupled cavity arrays. Selective qubit–qubit couplings are achieved by adiabatically eliminating the atomic excited states and photonic states, and the required phase shifts between the control qubit and any target qubit can be realized through suitable choices of the parameters of the external fields. Moreover, the effective model is robust against decoherence because neither the atoms nor the field modes are excited during the Gate Operation, leading to a useful step toward scalable quantum computing networks.

  • one step implementation of multiqubit phase Gate with one control qubit and multiple target qubits in coupled cavities
    arXiv: Quantum Physics, 2014
    Co-Authors: Hong-fu Wang, Aidong Zhu, Shou Zhang
    Abstract:

    We propose a one-step scheme to implement a multiqubit controlled phase Gate of one qubit simultaneously controlling multiple qubits with three-level atoms at distant nodes in coupled cavity arrays. The selective qubit-qubit couplings are achieved by adiabatically eliminating the atomic excited states and photonic states and the required phase shifts between the control qubit and any target qubit can be realized through suitable choices of the parameters of the external fields. Moreover, the effective model is robust against decoherence because neither the atoms nor the field modes during the Gate Operation are excited, leading to a useful step toward scalable quantum computing networks.

  • quantum Gate Operation with non instantaneous unitary kicks
    Optics Communications, 2011
    Co-Authors: Shou Zhang, Xiaoqiang Shao, Li Chen, Yongfang Zhao, Kyuhwang Yeon
    Abstract:

    Abstract A two-qubit controlled-z Gate is presented based on the non-instantaneous unitary kicks. Instead of putting two atoms through the cavity simultaneously, we make the atoms cross the cavity sequentially. The interaction between the second atom and the cavity plays the role for kicking the evolution of the system consisting of the first atom and cavity. By repeating the whole process N times, we obtain the controlled-z Gate with a high fidelity. The effects of decoherence such as spontaneous emission and the loss of cavity on the average Gate fidelity are investiGated in virtue of master equation. Furthermore the method for achieving the multi-qubit controlled-z Gate is also proposed.