## Publications and Research

#### Document Type

Article

#### Publication Date

2012

#### Abstract

Oscillations of superconducting current between clockwis e and counterclockwise directions in a flux qubit do not conserve the angular momentum of the qubit. T o compensate for this effect the solid containing the qubit must oscillate in unison with the current. This requires entanglement of quantum states of the qubit with quantum states of a macrosco pic body. The question then arises whether slow decoherence of quantum oscillations of the cur rent is consistent with fast decoherence of quantum states of a macroscopic solid. This problem is ana lyzed within an exactly solvable quantum model of a qubit embedded in an absolutely rigid soli d and for the elastic model that conserves the total angular momentum. We show that while the quantum state of a flux qubit is, in general, a mixture of a large number of rotational stat es, slow decoherence is permitted if the system is macroscopically large. Practical implicatio ns of entanglement of qubit states with mechanical rotations are discussed.

#### Recommended Citation

Chudnovsky, E. M., Garanin, D. A., & O'Keeffe, M. F. (2012). Conservation of angular momentum in a flux qubit. Journal of Superconductivity and Novel Magnetism, 25(4), 1007-1016. DOI: 10.1007/s10948-012-1410-y

## Comments

This is the pre-published version of this article.