Antihydrogen, the bound state of an antiproton and a positron, can be used as a test-bed of fundamental symmetries. In particular, the CPT theorem requires that hydrogen and antihydrogen have the same spectrum. The current experimental precision of measurements of hydrogen transition frequencies approaches 1 part in 1015. Similarly precise antihydrogen spectroscopy would constitute a unique, model-independent test of CPT symmetry. Antihydrogen atoms have been produced in quantity at CERN since 2002, when the ATHENA collaboration demonstrated  how to mix cryogenic plasmas of antiprotons and positrons to produce low energy anti-atoms. In this colloquium I will discuss the newest development along the road to antihydrogen spectroscopy: magnetically trapped antihydrogen. In November of 2010 the ALPHA collaboration reported  the first trapping of antihydrogen atoms in a magnetic multipole trap. The atoms must be produced with an energy - in temperature units - of less than 0.5 K in order to be trapped. Shortly afterward, ALPHA demonstrated that it was possible to store trapped antihydrogen atoms for up to 1000 seconds . I will discuss the many developments necessary to realise trapped antihydrogen, the ongoing efforts to resonantly interact with antihydrogen, and the future of antihydrogen physics at CERN.
 Amoretti, M. et al., Production and detection of cold antihydrogen atoms. Nature 419, 456 (2002).
 Andresen, G.B. et al., Trapped Antihydrogen, Nature, 468, 673 (2010).
 Andresen, G.B. et al., Confinement of antihydrogen for 1,000 seconds, Nature Physics, 7, 558 (2011).
Argonne Physics Division Colloquium Schedule