title: A low phase noise microwave source for atomic spin squeezing experiments in 87Rb.
abstract: We describe and characterize a simple, low cost, low phase noise microwave source that operates near 6.800 GHz for agile, coherent manipulation of ensembles of (87)Rb. Low phase noise is achieved by directly multiplying a low phase noise 100 MHz crystal to 6.8 GHz using a nonlinear transmission line and filtering the output with custom band-pass filters. The fixed frequency signal is single sideband modulated with a direct digital synthesis frequency source to provide the desired phase, amplitude, and frequency control. Before modulation, the source has a single sideband phase noise near -140 dBc/Hz in the range of 10 kHz-1 MHz offset from the carrier frequency and -130 dBc/Hz after modulation. The resulting source is estimated to contribute added spin-noise variance 16 dB below the quantum projection noise level during quantum nondemolition measurements of the clock transition in an ensemble 7 × 10(5) (87)Rb atoms.
authors.affiliation: JILA, National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA.
authors.forename: Zilong
authors.initials: Z
authors.lastname: Chen
authors.forename: Justin G
authors.initials: JG
authors.lastname: Bohnet
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Weiner
authors.forename: James K
authors.initials: JK
authors.lastname: Thompson