Fig. 1: Illustration of the coherence stabilization protocol.
From: Beating the Ramsey limit on sensing with deterministic qubit control
a Simulated trajectories of the Bloch vector in the xz plane for a qubit state which is either allowed to freely evolve (star markers; steady decay of vx) or stabilized with our protocol (triangle markers; stabilized vx up to a breakdown time, followed by steady decay), with T1 = T2 = 1 and vx(0) = 0.68. The black curve is the ∣v∣ = 1 limit for a pure state. b, c 3D Bloch sphere plot of the same trajectories for stabilization (b) and free evolution (c). d Pulse sequence schematic of our stabilization protocol. We prepare a state in the xz plane at an angle θ from the z-axis, then stabilize the Bloch component \({v}_{x}=\sin \theta\) up to a breakdown time. After the breakdown we turn off the control and the state is allowed to freely decay. After a variable evolution time we perform quantum state tomography.
