Michel, UlrichUlrichMichelKliesch, MartinMartinKlieschKueng, RichardRichardKuengGross, DavidDavidGross2022-11-182022-11-182018-11IEEE Transactions on Information Theory 64 (11): 8424239 (2018-11)http://hdl.handle.net/11420/14086The diamond norm plays an important role in quantum information and operator theory. Recently, it has also been proposed as a regularizer for low-rank matrix recovery. The norm constants that bound the diamond norm in terms of the nuclear norm (also known as trace norm) are explicitly known. This paper provides a simple characterization of all operators saturating the upper and lower bounds.en0018-944820181174437445Review Article10.1109/TIT.2018.2861887Other