Fig. 3: The infidelity parameter space for a servoed diode laser with a ΓFWHM = 1 Hz narrowed linewidth (ha = 4π × 1Hz).
a The frequency noise PSD of a LO generated from a servoed diode laser. Within the servo loop, the noise amplitude takes the value of ha. Above the servo bandwidth, ωsrv, the LO takes on the free-running laser noise including a relaxation oscillation peak of 20dB at 2π × 1GHz. b The infidelity landscape as the Rabi frequency and servo bandwidth are varied, demonstrating three main regions (detailed in text). The hb-limited region is separated by Ω = ωsrv (solid line) from the servo-limited region, with the χ-separation line (dashed) delineating the ha-limited region. c A 1D cross-section of (b) at Ω = π/2 × 105Hz. d A diagrammatic representation of noise spectral densities in each of the three regions, with the π − pulse filter function (in arbitrary units) overlaid for comparison. e The infidelity landscape as the above-servo noise amplitude, hb, and the servo bandwidth are varied for Ω = 2π × 10kHz. The β-separation line (dotted), does not guarantee qubit coherence, while the χ-separation line (dashed) again bounds the ha-limited region. f A cross-section of (e) at ωsrv = 300kHz. f A diagrammatic representation of the PSDs in each of the three regions with respect to the β- and χ-separation lines. The χ-separation line in Fourier space is given by Eq. 10.
