Maximally entangled states of two flux qubits in a microwave cavity

Migliore, Rosanna; Messina, A.

doi:10.1103/physrevb.72.214508

Cited by 22 publications

(23 citation statements)

References 41 publications

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“…Many strategies have been proposed to obtain a controllable coupling between qubits (see, e.g., [15,16,17,18,19,20,21,22,23,24]). Let us first study the superconducting circuit shown in Fig.…”

Section: A Variable-coupling Between Two Charge Qubitsmentioning

confidence: 99%

“…One-qubit and two-qubit quantum circuits (see, e.g., [5,6,7,8,9,10,11]) have been realized experimentally in superconducting systems. One of the most important issues in quantum information processing is how to couple two qubits, which has been widely studied theoretically and experimentally in superconducting quantum circuits (see, e.g., [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]). To couple two qubits, there are two types of approaches: (1) direct coupling and (2) indirect coupling.…”

Section: Introductionmentioning

confidence: 99%

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Generating stationary entangled states in superconducting qubits

Zhang

Liu

et al. 2009

Phys. Rev. A

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When a two-qubit system is initially maximally-entangled, two independent decoherence channels, one per qubit, would greatly reduce the entanglement of the two-qubit system when it reaches its stationary state. We propose a method on how to minimize such a loss of entanglement in open quantum systems. We find that the quantum entanglement of general two-qubit systems with controllable parameters can be protected by tuning both the single-qubit parameters and the twoqubit coupling strengths. Indeed, the maximum fidelity Fmax between the stationary entangled state, ρ∞, and the maximally-entangled state, ρm, can be about 2/3 ≈ max{tr(ρ∞ρm)} = Fmax, corresponding to a maximum stationary concurrence, Cmax, of about 1/3 ≈ C(ρ∞) = Cmax. This is significant because the quantum entanglement of the two-qubit system can be protected, even for a long time. We apply our proposal to several types of two-qubit superconducting circuits, and show how the entanglement of these two-qubit circuits can be optimized by varying experimentallycontrollable parameters.

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Section: A Variable-coupling Between Two Charge Qubitsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Generating stationary entangled states in superconducting qubits

Zhang

Liu

et al. 2009

Phys. Rev. A

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“…for the initial state is at most equal to 1, it is possible to show [15] that equation (4) is equivalent to a system of 64 coupled differential equations. This system can be numerically solved, which furnishes a description of the dynamics valid in a limited but, at the same time, physically meaningful interval of time.…”

Section: The Modelmentioning

confidence: 99%

Step-by-Step Control of the Dynamics of a Superconducting QED-like System

Migliore

Messina

Sánchez-Soto

2007

Open Syst. Inf. Dyn.

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We discuss the modus operandi of a theoretical scalable coupling scheme to control step by step the time evolution of a pair of flux qubits embedded in a lossy resonant cavity. The sequential interaction of each qubit with the quantized cavity mode is controlled by externally applied magnetic fluxes. Our analysis indicates that indirect qubit-qubit interactions, with the electromagnetic mode acting as a data bus, can be selectively performed and exploited both for the implementation of entangling gates and for the generation of states with a priori known characteristics.

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“…Josephson junctions can be operated as microwave resonators [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31]. In a previous work [32], a cavity QED approach [33] to characterizing the coupling between TLS's inside a Josephson junction and the junction resonator was suggested where a Jaynes-Cummings model was derived and the coupling between the TLS's and the resonator can be modulated with an applied magnetic field.…”

Section: Introductionmentioning

confidence: 99%

A Controllable Interaction Between Two-Level Systems Inside a Josephson Junction

Tian

Jacobs

2009

IEEE Trans. Appl. Supercond.

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Abstract-Two-level system fluctuators (TLS's) in the tunnel barrier of a Josephson junction have recently been demonstrated to cause novel energy splittings in spectroscopic measurements of superconducting phase qubits. With their strong coupling to the Josephson junction and relatively long decoherence times, TLS's can be considered as potential qubits and demonstrate coherent quantum effects. Here, we study the effective interaction between the TLS qubits that is mediated by a Josephson junction resonator driven by an external microwave source. This effective interaction can enable controlled quantum logic gates between the TLS's. Our study can be extended to other superconducting resonators coupling with TLS's.

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Maximally entangled states of two flux qubits in a microwave cavity

Cited by 22 publications

References 41 publications

Generating stationary entangled states in superconducting qubits

Generating stationary entangled states in superconducting qubits

Step-by-Step Control of the Dynamics of a Superconducting QED-like System

A Controllable Interaction Between Two-Level Systems Inside a Josephson Junction

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