Resonant quantum transitions in trapped antihydrogen atoms

• Published in: Nature (London) 2012-03, Vol.483 (7390), p.439-443
• Main Authors: Amole, C., Ashkezari, M. D., Baquero-Ruiz, M., Bertsche, W., Bowe, P. D., Butler, E., Capra, A., Cesar, C. L., Charlton, M., Deller, A., Donnan, P. H., Eriksson, S., Fajans, J., Friesen, T., Fujiwara, M. C., Gill, D. R., Gutierrez, A., Hangst, J. S., Hardy, W. N., Hayden, M. E., Humphries, A. J., Isaac, C. A., Jonsell, S., Kurchaninov, L., Little, A., Madsen, N., McKenna, J. T. K., Menary, S., Napoli, S. C., Nolan, P., Olchanski, K., Olin, A., Pusa, P., Rasmussen, C. Ø., Robicheaux, F., Sarid, E., Shields, C. R., Silveira, D. M., Stracka, S., So, C., Thompson, R. I., van der Werf, D. P., Wurtele, J. S.
• Format: Article
• Language: English
• Subjects: 639/638/403/908; 639/766/36; 639/766/483; Antihydrogen; Antimatter; Atom, molecule and ion trapping and colling methods; Atomic and molecular physics; Atomic beam spectroscopy; Atomic properties and interactions with photons; Atoms & subatomic particles; Charged particles; Constants; Cosmic rays; Decision trees; Ejection; Exact sciences and technology; Humanities and Social Sciences; Intensities and shapes of atomic spectral lines; letter; Line shapes, widths, and shifts; Mechanical control of atoms, molecules and ions; Methods; Microwave radiation; Microwaves; multidisciplinary; Physics; Science; Science (multidisciplinary); Studies; Survival; Trapping; Variables
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature10942

These authors demonstrate resonant quantum transitions in a pure antimatter atom—antihydrogen—by using microwave radiation to flip the spin of the positron of an anti-atom in a magnetic trap, thus ejecting the anti-atom. Towards antimatter spectroscopy The aim of the ALPHA experiment, which uses the Antiproton Decelerator at CERN, is to make a precision comparison of the spectra of atomic matter and antimatter, in the form of hydrogen and antihydrogen atoms. The comparison should allow a test of CPT (charge conjugation, parity and time reversal) symmetry, a fundamental part of the standard model of particle physics. This paper reports a first step in that direction. In a proof-of-principle experiment, the ALPHA team magnetically trapped cold antihydrogen atoms and observed their interaction with resonant microwave radiation. The group describes the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves. The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom’s stature lies in its simplicity and in the accuracy with which its spectrum can be measured 1 and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and—by comparison with measurements on its antimatter counterpart, antihydrogen—the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state 2 , 3 of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped 4 , 5 , 6 in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per att