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Banishing Quasiparticles From Josephson-Junction Qubits: Why and How To Do It



Kristine Lang, Sae Woo Nam, Joe Aumentado, John M. Martinis, C Urbina


Current-biased Josephson junctions are prime candidates for the implementation of quantum bits; however, a present limitation is their coherence time. In this paper we qualitatively describe the role of quasiparticles in decoherence. We discuss two methods to reduce the number of quasiparticles present in the junctions - current shunts to reduce the creation rate and normal-metal traps to increase the depletion rate. We evaluate the effectiveness of these methods with experimental data that demonstrates both reducing the quasiparticle number and increasing the coherence of the system. We conclude these methods are effective and that reducing the number of quasiparticles must be considered when designing Josephson junction qubits.
IEEE Transactions on Applied Superconductivity


Josephson junctions, qubits, superconductivity


Lang, K. , Nam, S. , Aumentado, J. , Martinis, J. and Urbina, C. (2003), Banishing Quasiparticles From Josephson-Junction Qubits: Why and How To Do It, IEEE Transactions on Applied Superconductivity (Accessed July 17, 2024)


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Created May 31, 2003, Updated October 12, 2021