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Spin Environment Engineering for a Persistent Current Qubit

Jacek Dziarmaga
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Abstract

A persistent current qubit has two quantum states with opposite currents flowing in a superconducting loop. Their magnetic field couple to nuclear spins. The qubit state is not only perturbed by the spins but it also gets entangled with the spins' state on a very short timescale. However, when the same spins are exposed to a strong but less than critical external magnetic field, then the qubit field is just a small perturbation on top of the external field and the entanglement with each spin is negligible. For a qubit which is more microscopic than certain threshold this partial entanglement results in negligible partial decoherence.

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Jacek Dziarmaga. 2001-01-30. Spin Environment Engineering for a Persistent Current Qubit. https://arxiv.org/abs/cond-mat/0101454

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