Non-Gaussian dephasing in flux qubits due to1∕fnoise

Abstract

Recent experiments by F. Yoshihara et al. [Phys. Rev. Lett. 97, 167001 (2006)] and by K. Kakuyanagi et al. (cond-mat/0609564) provided information on decoherence of the echo signal in Josephson-junction flux qubits at various bias conditions. These results were interpreted assuming a Gaussian model for the decoherence due to 1/f noise. Here we revisit this problem on the basis of the exactly solvable spin-fluctuator model reproducing detailed properties of the 1/f noise interacting with a qubit. We consider the time dependence of the echo signal and conclude that the results based on the Gaussian assumption need essential reconsideration.

Disentanglement and decoherence from classical non-Markovian noise: random telegraph noise

“…In these architectures, it is found that 1/ f noise is the dominant source of decoherence. Thus a thorough understanding of those experiments requires models that (a) deal with non-Markovian noises, especially random telegraph noises (RTN) [15] which are the basic building blocks of 1/ f noise; (b) treat dephasing together with relaxation [35][36][37][38][39][40][41].…”

Coherence of an Optically Illuminated Single Nuclear Spin Qubit

“…In this Letter, we investigate coherence properties of such an optically illuminated nuclear spin-electron spin system. We show that these properties are well-described by a spin-fluctuator model [9,10,11,12], involving a single nuclear spin (system) coupled by the hyperfine interaction to an electron [13] (fluctuator) that undergoes rapid optical transitions and mediates the coupling between the nuclear spin and the environment. We generalize the spin-fluctuator model to a vector description, necessary for single NV centers in diamond [1], and make direct comparisons with experiments.…”

Reduced visibility of Rabi oscillations in superconducting qubits

“…, 7), respectively, which indicates either substantial leakage out of the computational basis or a pronounced randomization of the state occupation over short time-scales. In the following, we discuss three possible mechanisms that result in a reduced visibility, namely (i) coherent coupling to a background fluctuator which induces transitions between the eigenstates of the superconducting micro-circuit [7]; (ii) population of higher excited states caused by a strong driving field, i.e., the AC current or voltage applied to drive Rabi oscillations; and (iii) the excitation of Bogoliubov quasi-particles.Background charge fluctuators are presently considered one of the dominant source of decoherence in superconducting qubits (squbits) [8,9,10,11]. However, the theoretical analysis of fluctuators has so far been focused on fluctuators with an incoherent dynamics which are coupled to the squbit by an Ising-like interaction.…”

“…Background charge fluctuators are presently considered one of the dominant source of decoherence in superconducting qubits (squbits) [8,9,10,11]. However, the theoretical analysis of fluctuators has so far been focused on fluctuators with an incoherent dynamics which are coupled to the squbit by an Ising-like interaction.…”