Looping on the Bloch sphere: Oscillatory effects in dephasing of qubits subject to broad-spectrum noise

Abstract

For many implementations of quantum computing, 1/f and other types of broad-spectrum noise are an important source of decoherence. An important step forward would be the ability to back out the characteristics of this noise from qubit measurements and to see if it leads to new physical effects. For certain types of qubits, the working point of the qubit can be varied. Using a new mathematical method that is suited to treat all working points, we present theoretical results that show how this degree of freedom can be used to extract noise parameters and to predict a new effect: noise-induced looping on the Bloch sphere. We analyze data on superconducting qubits to show that they are very near the parameter regime where this looping should be observed.

4 pages, 3 figures

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• Suppression of Decoherence and Disentanglement by the Exchange Interaction
• Quasi-Hamiltonian Method for Computation of Decoherence Rates
• Topology of Entanglement Evolution of Two Qubits
• An Ising-Glauber Spin Cluster Model for Temperature Dependent Magnetization Noise in SQUIDs
• Modeling of Low and High Frequency Noise by Slow and Fast Fluctuators
• Phenomenological noise model for superconducting qubits: two-state fluctuators and 1=f noise
• 1/f Flux Noise in low-T${}_c$ SQUIDs due to Superparamagnetic Phase Transitions in Defect Clusters
• Disappearance of entanglement: a topological point of view