  Here we present a sample of 12 massive quiescent galaxy candidates at z~3-4
observed with the James Webb Space Telescope (JWST) Near Infrared Spectrograph
(NIRSpec). These galaxies were pre-selected from the Hubble Space Telescope
imaging and 10 of our sources were unable to be spectroscopically confirmed by
ground based spectroscopy. By combining spectroscopic data from NIRSpec with
multi-wavelength imaging data from the JWST Near Infrared Camera (NIRCam), we
analyse their stellar populations and their formation histories. We find that
all of our galaxies classify as quiescent based on the reconstruction of their
star formation histories but show a variety of quenching timescales and ages.
All our galaxies are massive ($\sim0.1-1.2 \times 10^{11} M\odot$), with masses
comparable to massive galaxies in the local Universe. We find that the oldest
galaxy in our sample formed $\sim1.0\times10^{11} M\odot$ of mass within the
first few hundred million years of the Universe and has been quenched for more
than a billion years by the time of observation at z$\sim$3.2 ($\sim$2 billion
years after the Big Bang). Our results point to very early formation of massive
galaxies requiring a high conversion rate of baryons to stars in the early
Universe.
