24 August 2004 Characterizing a superconducting charge qubit via environmental noise
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In this paper, we propose a technique to characterise the energy level structure of a superconducting charge qubit. The technique relies on the backreaction of a solid-state qubit on its environment and the incoherent transfer of energy from a high frequency mode to a low frequency mode due to the stochastic transitions of the qubit between energy eigenstates. We consider a coupled system consisting of a model charge qubit and several classical degrees of freedom. The qubit is coupled to three electromagnetic modes: a low frequency bias field, a higher frequency mode (which is used to pump the qubit from the ground state to an excited state), and a lossy reservoir (which represents the cavity that contains the qubit and control fields). The reservoir provides a mechanism to allow the qubit to dissipate energy and to induce spontaneous decays from an excited state into the ground state. We show that these spontaneous decays can have a significant effect on the noise in the classical bias field, and that this noise can be used to characterise the energy level structure of the qubit.
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Jason F. Ralph, Jason F. Ralph, Elias J Griffith, Elias J Griffith, Terence D. Clark, Terence D. Clark, Mark J. Everitt, Mark J. Everitt, Peter Stiffell, Peter Stiffell, } "Characterizing a superconducting charge qubit via environmental noise", Proc. SPIE 5436, Quantum Information and Computation II, (24 August 2004); doi: 10.1117/12.541492; https://doi.org/10.1117/12.541492

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