Liu Yang

Tsinghua University, Beijing, Beijing Shi, China

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Publications (6)5.69 Total impact

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    ABSTRACT: In this paper, we study the control problem of adiabatic decoherence in a three-level atom. We will find the decoupling bang-bang group for various configurations, including the V configuration and the cascade type of three-level atom subjected to adiabatic decoherence. We also give the programs to design a sequence of periodic twinborn pulses to suppress the decoherence.
    Communications in Theoretical Physics 04/2009; 44(5):810. · 0.95 Impact Factor
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    Liu Xiao-Shu, Liu Yang
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    ABSTRACT: In this paper, we have detailedly studied the dynamical suppression of the phase damping for the two-qubit quantum memory of Ising model by the quantum ``bang-bang" technique. We find the sequence of periodic radio-frequency pulses repetitively to flip the state of the two-qubit system and quantitatively find that these pulses can be used to effectively suppress the phase damping decoherence of the quantum memory and freeze the system state into its initial state. The general sequence of periodic radio-frequency pulses to suppress the phase damping of multi-qubit of Ising model is also given.
    Communications in Theoretical Physics 04/2009; 44(3):459. · 0.95 Impact Factor
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    Long Gui-Lu, Liu Yang, Wang Chuan
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    ABSTRACT: In this paper, we give the most general duality gates, or generalized quantum gates in duality quantum computers. Here we show by explicit construction that a n-bit duality quantum computer with d slits can be simulated perfectly with an ordinary quantum computer with n qubits and one auxiliary qudit. Using this model, we give the most general form of duality gates which is of the form Σd-1i = 0 pi U i, and the pi's are complex numbers with module less or equal to 1 and constrained by |Σi pi|≤1.
    Communications in Theoretical Physics 01/2009; 51(1):65. · 0.95 Impact Factor
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    Long Gui-Lu, Liu Yang
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    ABSTRACT: In this letter, we propose a duality computing mode, which resembles particle-wave duality property when a quantum system such as a quantum computer passes through a double-slit. In this mode, computing operations are not necessarily unitary. The duality mode provides a natural link between classical computing and quantum computing. In addition, the duality mode provides a new tool for quantum algorithm design.
    Communications in Theoretical Physics 01/2009; 50(6):1303. · 0.95 Impact Factor
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    ABSTRACT: We propose a scheme of quantum computation with nonlinear quantum optics. Polarization states of photons are used for qubits. Photons with different frequencies represent different qubits. Single qubit rotation operation is implemented through optical elements like the Faraday polarization rotator. Photons are separated into different optical paths, or merged into a single optical path using dichromatic mirrors. The controlled-NOT gate between two qubits is implemented by the proper combination of parametric up and down conversions. This scheme has the following features: (1) No auxiliary qubits are required in the controlled-NOT gate operation; (2) No measurement is required in the course of the computation; (3) It is resource efficient and conceptually simple.
    Communications in Theoretical Physics 02/2008; 49(1):107. · 0.95 Impact Factor
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    ABSTRACT: The ground state entanglement in an isotropic three-qubit transverse XY chain with energy current is analysed. A quantum phase transition from a no-energy-current phase to energy-current phase is found when the magnetic field changes. It has also been found that the ground state changes in company with the quantum phase transition.
    Chinese Physics Letters 01/2007; 24(1):8. · 0.92 Impact Factor