I am co-PI (with Nao Suzuki) of the SUbaru Supernovae with Hubble Infrared (SUSHI) program. We are more than doubling the number of well-measured, distant (redshift >~ 1.1) supernovae Ia to significantly improve our measurements of the expansion history of the Universe.
Other work I have done with distant SNe includes:
Gravitationally amplified SNe in Cluster Lensing And Supernova survey with Hubble (CLASH)
and the then most-distant spectroscopically confirmed SN Ia