Bloch-sphere approach to correlated noise in coupled qubits

Abstract

By use of a generalized Bloch vector construction, we study the decoherence of a system composed of two interacting qubits in a noisy environment. In particular, we investigate the effects of correlations in the noise acting on distinct qubits. Our treatment of the two-qubit system by use of the generalized Bloch vector leads to tractable analytic equations for the dynamics of the 4-level Bloch vector and allows for the application of geometrical concepts from the well known 2-level Bloch sphere. We find that in the presence of correlated or anticorrelated noise, the rate of decoherence is very sensitive to the initial twoqubit state, as well as to the symmetry of the Hamiltonian. In the absence of symmetry in the Hamiltonian, correlations only weakly impact the decoherence rate.

The dynamics of two entangled qubits exposed to classical noise: role of spatial and temporal noise correlations

“…The exact solution is impossible to obtain, and below we will only give a rather brief discussion of possible approximate analytical solutions with some results of exact simulations added to illustrate the main points. Since the topic of influence of transverse noise on coherence and entanglement dynamics is quite involved [29,37,38,58,59] the aim of this section is to give only a qualitative picture.…”

“…[27], and the case of transverse coupling to a more general class of noise (of 1/f type, both Gaussian and non-Gaussian) was considered in Refs. [23,26], and in [28,29] where the influence qubit-qubit coupling was also studied.…”

1/f noise: implications for solid-state quantum information

“…These approaches also predict the existence of operating conditions where leading order effects of 1/f fluctuations are eliminated also for complex architectures, analogously to the single qubit "optimal point". The effect of 1/f noise in solid state complex architectures is a subject of current investigation (Bellomo et al, 2010;Brox et al, 2012;D'Arrigo et al, 2008;D'Arrigo and Paladino, 2012;Hu et al, 2007;Paladino et al, 2009Paladino et al, , 2011Paladino et al, , 2010Storcz et al, 2005). Considerable improvement in minimizing sensitivity to charge noise has been reached via clever engineering, in particular in the cQED architecture, see Sec.…”

Characterize noise correlation and enhance coherence via qubit motion

“…In the previous studies, there have been several experimental protocols for determining nearest-neighbor-qubit noise correlation [19][20][21][22][23][24][25][26][27][28] in different quantum systems, but there is few work for characterizing noise correlation between qubits with long-range spacial distances (non-nearest neighbors). A recent work [29] proposed a method to construct a quantum noise correlation matrix allowing visualization of correlations between all pairs of qubits, but the method is relatively complicated to implement experimentally.…”