Entangled Macroscopic Quantum States in Two Superconducting Qubits

Berkley, A. J.; Xu, Haitan; Ramos, Roberto; Gubrud, M. A.; Strauch, Frederick W.; Johnson, Philip R.; Anderson, J. R.; Dragt, Alex J.; Lobb, C. J.; Wellstood, F. C.

doi:10.1126/science.1084528

Cited by 423 publications

(326 citation statements)

References 16 publications

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“…For this reason, there has been an increasing interest in establishing the conditions under which entanglement between macroscopic objects can arise. Relevant experimental demonstration in this directions are given by the entanglement between collective spins of atomic ensembles [36], and between Josephson-junction qubits [37]. Then, starting from the proposal of Ref.…”

Section: Introductionmentioning

confidence: 99%

Robust entanglement of a micromechanical resonator with output optical fields

et al. 2008

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We perform an analysis of the optomechanical entanglement between the experimentally detectable output field of an optical cavity and a vibrating cavity end-mirror. We show that by a proper choice of the readout (mainly by a proper choice of detection bandwidth) one can not only detect the already predicted intracavity entanglement but also optimize and increase it. This entanglement is explained as being generated by a scattering process owing to which strong quantum correlations between the mirror and the optical Stokes sideband are created. All-optical entanglement between scattered sidebands is also predicted and it is shown that the mechanical resonator and the two sideband modes form a fully tripartite-entangled system capable of providing practicable and robust solutions for continuous variable quantum communication protocols.

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Section: Introductionmentioning

confidence: 99%

Robust entanglement of a micromechanical resonator with output optical fields

et al. 2008

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“…However, in superconducting-qubit based quantum computation, ac fields (e.g., microwave fields) are usually used to manipulate the qubit's state. [1,2,3,4,5,6,7,8,9,10,11,12,18] Recent experiment [14] shows that the decoherence time of a superconducting qubit is significantly increased in the presence of a resonantly ac driving field. Thus a comprehensive understanding to decoherence of a realistic superconducting qubit needs to include influence of driving fields.…”

Section: Introductionmentioning

confidence: 99%

Relaxation and decoherence in a resonantly driven qubit

Zhou

Chu

Han

2008

J. Phys. B: At. Mol. Opt. Phys.

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Relaxation and decoherence of a qubit coupled to environment and driven by a resonant ac field are investigated by analytically solving Bloch equation of the qubit. It is found that the decoherence of a driven qubit can be decomposed into intrinsic and field-dependent ones. The intrinsic decoherence time equals to the decoherence time of the qubit in free decay while the fielddependent decoherence time is identical with the relaxation time of the qubit in driven oscillation. Analytical expressions of the relaxation and decoherence times are derived and applied to study a microwave-driven SQUID flux qubit. The results are in excellent agreement with those obtained by numerically solving the master equation. The relations between the relaxation and decoherence times of a qubit in free decay and driven oscillation can be used to extract the decoherence and thus dephasing times of the qubit by measuring its population evolution in free decay and resonantly driven oscillation.

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“…Superconducting qubits utilize charge [5][6][7] or flux [8] degrees of freedom, or energy levels quantization in a single current-biased Josephson junction [9,10]. Inter-qubit coupling [15][16][17][18][19][20] and also quantum logic gates [21][22][23] have been reported later. Further progress in the field slowed down due to obvious decoherence issues that are still to be overcome in order to implement a working quantum computer.…”

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confidence: 96%

Josephson charge qubits: a brief review

Pashkin

Astafiev

Yamamoto

et al. 2009

Quantum Inf Process

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The field of solid-state quantum computation is expanding rapidly initiated by our original charge qubit demonstrations. Various types of solid-state qubits are being studied, and their coherent properties are improving. The goal of this review is to summarize achievements on Josephson charge qubits. We cover the results obtained in our joint group of NEC Nano Electronics Research Laboratories and RIKEN Advanced Science Institute, also referring to the works done by other groups. Starting from a short introduction, we describe the principle of the Josephson charge qubit, its manipulation and readout. We proceed with coupling of two charge qubits and implementation of a logic gate. We also discuss decoherence issues. Finally, we show how a charge qubit can be used as an artificial atom coupled to a resonator to demonstrate lasing action.

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Entangled Macroscopic Quantum States in Two Superconducting Qubits

Cited by 423 publications

References 16 publications

Robust entanglement of a micromechanical resonator with output optical fields

Robust entanglement of a micromechanical resonator with output optical fields

Relaxation and decoherence in a resonantly driven qubit

Josephson charge qubits: a brief review

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