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Robust Conditional z Gate Operation in the Decoherence-Free Subspace of Superconducting Quantum-Interference Devices

Xiao‐Qiang Shao, Li Chen, Shou Zhang +1 more

International Journal of Theoretical PhysicsJul 6, 20091 citation

Preparation of three- and four-qubit decoherence-free states via Zeno-like measurements

Xiao‐Qiang Shao, Li Chen, Shou Zhang +2 more

Enlightened by the idea of purification through Zeno-like measurements (Nakazato et al 2003 Phys. Rev. Lett. 90 060401), we propose a scheme for generating three- and four-qubit decoherence-free states with respect to collective amplitude damping. The whole system is in a star configuration of a spin network and the outer spin qubits construct the decoherence-free state via measuring the state of central spin qubit at intervals of τ repeatedly. An interesting feature is found: namely, that in order to prepare the three-qubit decoherence-free state successfully, the value of τ for the projected time-evolution operator must be set definitely, while this restrictive condition is relaxed for achieving the four-qubit decoherence-free state. The simulation results reveal that the fidelity approaches one asymptotically, and the corresponding success probability reaches a stable value by increasing the number of measurements N.Enlightened by the idea of purification through Zeno-like measurements (Nakazato et al 2003 Phys. Rev. Lett. 90 060401), we propose a scheme for generating three- and four-qubit decoherence-free states with respect to collective amplitude damping. The whole system is in a star configuration of a spin network and the outer spin qubits construct the decoherence-free state via measuring the state of central spin qubit at intervals of τ repeatedly. An interesting feature is found: namely, that in order to prepare the three-qubit decoherence-free state successfully, the value of τ for the projected time-evolution operator must be set definitely, while this restrictive condition is relaxed for achieving the four-qubit decoherence-free state. The simulation results reveal that the fidelity approaches one asymptotically, and the corresponding success probability reaches a stable value by increasing the number of measurements N.

Journal of Physics B Atomic Molecular and Optical PhysicsJun 17, 201010 citations

Generation of Entangled States of Multiple Superconducting Quantum Interference Devices in Cavity

Zhan Zhan, Zhiming, LI . +2 more

理论物理通讯：英文版Jan 1, 20060 citations

Generating arbitrary four-qubit decoherence-free states via two singlet states and a partial exchanging device

Yan-Xiao Gong, Xu‐Bo Zou, Xiao-Ling Niu +4 more

We clarify the original thought for the scheme in our recent paper (Phys. Rev. A, 77, 042317), for preparing arbitrary four‐qubit decoherence‐free states robust against collective decoherence. Our method needs two singlet states and a tunable partial exchanging device.

AIP conference proceedingsJan 1, 20090 citations

Suppressing decoherence of superconducting qubits by trapping non-equilibrium quasiparticles

Yvonne Y. Gao, Chen Wang, Ioan M. Pop +9 more

Bulletin of the American Physical SocietyMar 6, 20150 citations

Universal quantum computation in a decoherence-free subspace for the σx -type collective noise with superconducting charge qubits

Zu-Rong Zhang, Chunyan Li, Chun-Wang Wu +2 more

We propose an encoding scheme to fight against ${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\ensuremath{\sigma}}}_{x}$-type local collective noise. In our scheme, a logical qubit consists of two charge qubits coupled by a variable capacitance, and different logical qubits are coupled by a common inductance. A logical qubit provides a decoherence-free subspace (DFS) immune to the ${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\ensuremath{\sigma}}}_{x}$-type collective noise. We show how to realize universal quantum computation in the DFS. Any two logical qubits can be selectively and controllably coupled by adjusting fluxes through the common inductance and superconducting-quantum-interference-device loops, which makes it possible to scale our scheme up to a large number of logical qubits. Finally, we show how to prepare a logical qubit in the DFS.We propose an encoding scheme to fight against ${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\ensuremath{\sigma}}}_{x}$-type local collective noise. In our scheme, a logical qubit consists of two charge qubits coupled by a variable capacitance, and different logical qubits are coupled by a common inductance. A logical qubit provides a decoherence-free subspace (DFS) immune to the ${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{\ensuremath{\sigma}}}_{x}$-type collective noise. We show how to realize universal quantum computation in the DFS. Any two logical qubits can be selectively and controllably coupled by adjusting fluxes through the common inductance and superconducting-quantum-interference-device loops, which makes it possible to scale our scheme up to a large number of logical qubits. Finally, we show how to prepare a logical qubit in the DFS.

Physical Review AOct 17, 20126 citations

Robust preparation of four-qubit decoherence-free states for superconducting quantum interference devices against collective amplitude damping

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Robust preparation of four-qubit decoherence-free states for superconducting quantum interference devices against collective amplitude damping

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