Experimental characterization of the two current states in a Nb persistent-current qubit

Segall, K.; Crankshaw, D.S.; Nakada, D.; Singh, Bhagwan; Lee, J.; Orlando, Terry P.; Berggren, Karl K.; Marković, Nina; Valenzuela, Sergio O.; Tinkham, M.

doi:10.1109/tasc.2003.814126

Cited by 5 publications

(5 citation statements)

References 4 publications

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“…The width, which should be minimized, depends on the rate at which the barrier is raised, thermalization between the states in left and right wells, and flux noise in the tilt bias near the minimum gap 10,12,13,[20][21][22][23][24][25] . In an annealing process, minimizing the s-curve width improves performance by increasing the qubit's sensitivity to other qubits it is coupled to and increases the dynamic range of couplers by making it easier to induce a detectable shift in the qubit's state.…”

Section: S-curve Width Reduction Via Annealing Path Controlmentioning

confidence: 99%

Anneal-path correction in flux qubits

et al. 2021

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Quantum annealers require accurate control and optimized operation schemes to reduce noise levels, in order to eventually demonstrate a computational advantage over classical algorithms. We study a high coherence four-junction capacitively shunted flux qubit (CSFQ), using dispersive measurements to extract system parameters and model the device. Josephson junction asymmetry inherent to the device causes a deleterious nonlinear cross-talk when annealing the qubit. We implement a nonlinear annealing path to correct the asymmetry in situ, resulting in a substantial increase in the probability of the qubit being in the correct state given an applied flux bias. We also confirm the multi-level structure of our CSFQ circuit model by annealing it through small spectral gaps and observing quantum signatures of energy level crossings. Our results demonstrate an anneal-path correction scheme designed and implemented to improve control accuracy for high-coherence and high-control quantum annealers, which leads to an enhancement of success probability in annealing protocols.

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Section: S-curve Width Reduction Via Annealing Path Controlmentioning

confidence: 99%

Anneal-path correction in flux qubits

et al. 2021

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“…The flux qubit coupled to the SQUID is an effective dissipative two state system and can be studied in the spin-boson model. The ohmic regime when the condition res LC ω ω is fulfilled may be realized experimentally with Niobium-based technology [10]. In the following we discuss the system in this frequency regime.…”

Section: Decoherence -Low Temperature Regimementioning

confidence: 99%

Decoherence in flux qubits on mesoscopic nonsuperconducting rings

Kurpas

Dajka

Zipper

2007

Physica Status Solidi (b)

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The problem of decoherence in recently proposed flux qubits built on mesoscopic normal metal rings is studied. The relaxation and dephasing times coming from the interaction of the qubit with the measuring device are calculated within the weak coupling spin-boson model. We analyze the effect of the measuring apparatus on the relaxation and dephasing times. The possibility of ohmic approximation for the bath is investigated. Considerably long decoherence times are found. The work is limited to the weak damping regime in low temperatures.

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“…The process is capable of yielding submicrometer Josephson junctions critical for the persistent-current qubit approach using i-line photolithography on 150-mm-diameter wafers [33]. Devices developed under this process have been used by multiple groups to realize superconductive quantum circuits [98], [99], [100].…”

Section: Scaling Upmentioning

confidence: 99%