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Four ppm measurement of the antihydrogen ground-state hyperfine splitting

R. Akbari, L. O. de Araujo Azevedo, Christopher Baker Orcid Logo, W. Bertsche, Nishant Bhatt, G. Bonomi Orcid Logo, A. Capra Orcid Logo, I. Carli Orcid Logo, C. L. Cesar Orcid Logo, Michael Charlton, April Cridland Orcid Logo, A. Del Vincio, D. Duque Quiceno Orcid Logo, Stefan Eriksson Orcid Logo, A. Evans, J. Fajans Orcid Logo, T. Friesen Orcid Logo, M. C. Fujiwara, Lukas Golino, Maria Gomes Goncalves, J. S. Hangst Orcid Logo, M. E. Hayden, P. Heidari, D. Hodgkinson Orcid Logo, Aled Isaac Orcid Logo, S. A. Jones Orcid Logo, S. Jonsell Orcid Logo, Niels Madsen Orcid Logo, V. R. Marshall, J. T. K. McKenna, T. Momose Orcid Logo, J. Nauta Orcid Logo, A. N. Oliveira Orcid Logo, A. Powell Orcid Logo, C. Ø. Rasmussen Orcid Logo, Tom Robertson-Brown, F. Robicheaux Orcid Logo, R. L. Sacramento, E. Sarid, Joos Schoonwater, D. M. Silveira, J. Singh Orcid Logo, G. Smith Orcid Logo, C. So, S. Stracka Orcid Logo, J. Suh Orcid Logo, A. G. Swadling, T. D. Tharp, Kurt Thompson, R. I. Thompson, E. Thorpe-Woods Orcid Logo, A. J. Uribe Jimenez Orcid Logo, M. Urioni Orcid Logo, D. P. van de Werf Orcid Logo, S. G. Wilson Orcid Logo, P. Woosaree Orcid Logo, J. S. Wurtele Orcid Logo, (The ALPHA Collaboration), C. L. Cesar, A. Del Vincio, D. P. van de Werf, EDWARD THORPE-WOODS, Dirk van der Werf

Nature, Volume: 653, Issue: 8116, Pages: 1022 - 1026

Swansea University Authors: Christopher Baker Orcid Logo, Nishant Bhatt, Michael Charlton, April Cridland Orcid Logo, Stefan Eriksson Orcid Logo, Lukas Golino, Maria Gomes Goncalves, Aled Isaac Orcid Logo, Niels Madsen Orcid Logo, Tom Robertson-Brown, Joos Schoonwater, Kurt Thompson, EDWARD THORPE-WOODS, Dirk van der Werf

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DOI (Published version): 10.1038/s41586-026-10556-x

Abstract

The hydrogen atom is a touchstone for the foundations, evolution and frontiers of quantum theory. Key spectral lines of this atom have been determined to remarkable precision. Our research focuses on the study of antihydrogen, the antimatter counterpart of hydrogen. We test fundamental symmetries of...

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Published in: Nature
ISSN: 0028-0836 1476-4687
Published: Springer Science and Business Media LLC 2026
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URI: https://cronfa.swan.ac.uk/Record/cronfa72005
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At this level, our measurement is sensitive to the internal structure of the antiproton, which contributes at about 40 ppm and is approaching the limit of existing theoretical analyses. The gains we report are the product of marked advances in magnetic trap field control, stabilization and characterization; anti-atom spin-state manipulation; and improved antihydrogen accumulation rate.</abstract><type>Journal Article</type><journal>Nature</journal><volume>653</volume><journalNumber>8116</journalNumber><paginationStart>1022</paginationStart><paginationEnd>1026</paginationEnd><publisher>Springer Science and Business Media LLC</publisher><placeOfPublication/><isbnPrint/><isbnElectronic/><issnPrint>0028-0836</issnPrint><issnElectronic>1476-4687</issnElectronic><keywords/><publishedDay>28</publishedDay><publishedMonth>5</publishedMonth><publishedYear>2026</publishedYear><publishedDate>2026-05-28</publishedDate><doi>10.1038/s41586-026-10556-x</doi><url>https://doi.org/10.1038/s41586-026-10556-x</url><notes/><college>COLLEGE NANME</college><department>Engineering and Applied Sciences School</department><CollegeCode>COLLEGE CODE</CollegeCode><DepartmentCode>EAAS</DepartmentCode><institution>Swansea University</institution><apcterm>External research funder(s) paid the OA fee (includes OA grants disbursed by the Library)</apcterm><funders>CNPq, FAPERJ, RENAFAE (Brazil); NSERC, NRC/TRIUMF, EHPDS/EHDRS, CFI, DRAC (Canada); FNU (Nice Centre), Carlsberg Foundation (Denmark); STFC, EPSRC, the Royal Society and the Leverhulme Trust (the UK); DOE, NSF (the USA); ISF (Israel); and VR (Sweden)</funders><projectreference/><lastEdited>2026-06-03T08:02:04.1151845</lastEdited><Created>2026-06-03T07:53:35.3358182</Created><path><level id="1">Faculty of Science and Engineering</level><level id="2">School of Biosciences, Geography and Physics - Physics</level></path><authors><author><firstname>R.</firstname><surname>Akbari</surname><order>1</order></author><author><firstname>L. 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Key spectral lines of this atom have been determined to remarkable precision. Our research focuses on the study of antihydrogen, the antimatter counterpart of hydrogen. We test fundamental symmetries of nature (such as simultaneous charge conjugation, parity inversion, and time reversal or CPT symmetry) through precision comparisons of these atomic systems. Recent 1S–2S spectroscopic measurements on trapped antihydrogen have achieved relative precisions of parts per trillion. However, the ground-state hyperfine splitting, which is sensitive to the internal structure of the antiproton, has only been measured to 400 parts per million (ppm). Here we report a 4 ppm measurement of the antihydrogen ground-state hyperfine splitting energy a1S, advancing the state-of-the-art precision by two orders of magnitude. From microwave spectroscopy experiments with roughly 24,000 anti-atoms, we determine in a 1-T magnetic field, consistent with expectations for hydrogen. At this level, our measurement is sensitive to the internal structure of the antiproton, which contributes at about 40 ppm and is approaching the limit of existing theoretical analyses. The gains we report are the product of marked advances in magnetic trap field control, stabilization and characterization; anti-atom spin-state manipulation; and improved antihydrogen accumulation rate. Journal Article Nature 653 8116 1022 1026 Springer Science and Business Media LLC 0028-0836 1476-4687 28 5 2026 2026-05-28 10.1038/s41586-026-10556-x https://doi.org/10.1038/s41586-026-10556-x COLLEGE NANME Engineering and Applied Sciences School COLLEGE CODE EAAS Swansea University External research funder(s) paid the OA fee (includes OA grants disbursed by the Library) CNPq, FAPERJ, RENAFAE (Brazil); NSERC, NRC/TRIUMF, EHPDS/EHDRS, CFI, DRAC (Canada); FNU (Nice Centre), Carlsberg Foundation (Denmark); STFC, EPSRC, the Royal Society and the Leverhulme Trust (the UK); DOE, NSF (the USA); ISF (Israel); and VR (Sweden) 2026-06-03T08:02:04.1151845 2026-06-03T07:53:35.3358182 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Physics R. Akbari 1 L. O. de Araujo Azevedo 2 Christopher Baker 0000-0002-9448-8419 3 W. Bertsche 4 Nishant Bhatt 5 G. Bonomi 0000-0003-1618-9648 6 A. Capra 0000-0001-9499-0380 7 I. Carli 0000-0002-0411-1141 8 C. L. Cesar 0000-0003-2638-0032 9 Michael Charlton 10 April Cridland 0000-0003-4361-0266 11 A. Del Vincio 12 D. Duque Quiceno 0009-0000-4625-3757 13 Stefan Eriksson 0000-0002-5390-1879 14 A. Evans 15 J. Fajans 0000-0002-4403-6027 16 T. Friesen 0000-0002-7017-9662 17 M. C. Fujiwara 18 Lukas Golino 19 Maria Gomes Goncalves 20 J. S. Hangst 0000-0001-5288-2330 21 M. E. Hayden 22 P. Heidari 23 D. Hodgkinson 0000-0003-3410-5540 24 Aled Isaac 0000-0002-7813-1903 25 S. A. Jones 0000-0001-8205-2186 26 S. Jonsell 0000-0003-4969-1714 27 Niels Madsen 0000-0002-7372-0784 28 V. R. Marshall 29 J. T. K. McKenna 30 T. Momose 0000-0001-8976-1938 31 J. Nauta 0000-0002-3477-7104 32 A. N. Oliveira 0000-0003-1567-7981 33 A. Powell 0000-0003-2475-6067 34 C. Ø. Rasmussen 0000-0002-6029-1730 35 Tom Robertson-Brown 36 F. Robicheaux 0000-0002-8054-6040 37 R. L. Sacramento 38 E. Sarid 39 Joos Schoonwater 40 D. M. Silveira 41 J. Singh 0000-0002-2981-9234 42 G. Smith 0009-0005-9784-5273 43 C. So 44 S. Stracka 0000-0003-0013-4714 45 J. Suh 0009-0006-9261-115x 46 A. G. Swadling 47 T. D. Tharp 48 Kurt Thompson 49 R. I. Thompson 50 E. Thorpe-Woods 0009-0001-2349-810x 51 A. J. Uribe Jimenez 0000-0001-6331-0266 52 M. Urioni 0000-0002-4455-7383 53 D. P. van de Werf 0000-0001-5436-5214 54 S. G. Wilson 0009-0000-5020-4480 55 P. Woosaree 0009-0003-5969-8909 56 J. S. Wurtele 0000-0001-8401-0297 57 (The ALPHA Collaboration) 58 C. L. Cesar 59 A. Del Vincio 60 D. P. van de Werf 61 EDWARD THORPE-WOODS 62 Dirk van der Werf 63
title Four ppm measurement of the antihydrogen ground-state hyperfine splitting
spellingShingle Four ppm measurement of the antihydrogen ground-state hyperfine splitting
Christopher Baker
Nishant Bhatt
Michael Charlton
April Cridland
Stefan Eriksson
Lukas Golino
Maria Gomes Goncalves
Aled Isaac
Niels Madsen
Tom Robertson-Brown
Joos Schoonwater
Kurt Thompson
EDWARD THORPE-WOODS
Dirk van der Werf
title_short Four ppm measurement of the antihydrogen ground-state hyperfine splitting
title_full Four ppm measurement of the antihydrogen ground-state hyperfine splitting
title_fullStr Four ppm measurement of the antihydrogen ground-state hyperfine splitting
title_full_unstemmed Four ppm measurement of the antihydrogen ground-state hyperfine splitting
title_sort Four ppm measurement of the antihydrogen ground-state hyperfine splitting
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author_id_fullname_str_mv 0c72afb63bd0c6089fc5b60bd096103e_***_Christopher Baker
6f0aa23156c022c29720a1b3a6a2f2df_***_Nishant Bhatt
d9099cdd0f182eb9a1c8fc36ed94f53f_***_Michael Charlton
e3c734cfda1e0b3835968762f39525cc_***_April Cridland
785cbd474febb1bfa9c0e14abaf9c4a8_***_Stefan Eriksson
d9d18e9c25d4356d501a05686aac5f4e_***_Lukas Golino
e36176626ecde930c5fe4a95d84e7e12_***_Maria Gomes Goncalves
06d7ed42719ef7bb697cf780c63e26f0_***_Aled Isaac
e348e4d768ee19c1d0c68ce3a66d6303_***_Niels Madsen
b156aea3e3d17cbaa7c88b2cbda685c0_***_Tom Robertson-Brown
015c50bdb7662cdce2dbd7ae8b72abf9_***_Joos Schoonwater
8d092bff80ec4e68bd02830ffe2ff179_***_Kurt Thompson
5cd0756f57de65df317724e6d8365e16_***_EDWARD THORPE-WOODS
4a4149ebce588e432f310f4ab44dd82a_***_Dirk van der Werf
author Christopher Baker
Nishant Bhatt
Michael Charlton
April Cridland
Stefan Eriksson
Lukas Golino
Maria Gomes Goncalves
Aled Isaac
Niels Madsen
Tom Robertson-Brown
Joos Schoonwater
Kurt Thompson
EDWARD THORPE-WOODS
Dirk van der Werf
author2 R. Akbari
L. O. de Araujo Azevedo
Christopher Baker
W. Bertsche
Nishant Bhatt
G. Bonomi
A. Capra
I. Carli
C. L. Cesar
Michael Charlton
April Cridland
A. Del Vincio
D. Duque Quiceno
Stefan Eriksson
A. Evans
J. Fajans
T. Friesen
M. C. Fujiwara
Lukas Golino
Maria Gomes Goncalves
J. S. Hangst
M. E. Hayden
P. Heidari
D. Hodgkinson
Aled Isaac
S. A. Jones
S. Jonsell
Niels Madsen
V. R. Marshall
J. T. K. McKenna
T. Momose
J. Nauta
A. N. Oliveira
A. Powell
C. Ø. Rasmussen
Tom Robertson-Brown
F. Robicheaux
R. L. Sacramento
E. Sarid
Joos Schoonwater
D. M. Silveira
J. Singh
G. Smith
C. So
S. Stracka
J. Suh
A. G. Swadling
T. D. Tharp
Kurt Thompson
R. I. Thompson
E. Thorpe-Woods
A. J. Uribe Jimenez
M. Urioni
D. P. van de Werf
S. G. Wilson
P. Woosaree
J. S. Wurtele
(The ALPHA Collaboration)
C. L. Cesar
A. Del Vincio
D. P. van de Werf
EDWARD THORPE-WOODS
Dirk van der Werf
format Journal article
container_title Nature
container_volume 653
container_issue 8116
container_start_page 1022
publishDate 2026
institution Swansea University
issn 0028-0836
1476-4687
doi_str_mv 10.1038/s41586-026-10556-x
publisher Springer Science and Business Media LLC
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Physics{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Physics
url https://doi.org/10.1038/s41586-026-10556-x
document_store_str 0
active_str 0
description The hydrogen atom is a touchstone for the foundations, evolution and frontiers of quantum theory. Key spectral lines of this atom have been determined to remarkable precision. Our research focuses on the study of antihydrogen, the antimatter counterpart of hydrogen. We test fundamental symmetries of nature (such as simultaneous charge conjugation, parity inversion, and time reversal or CPT symmetry) through precision comparisons of these atomic systems. Recent 1S–2S spectroscopic measurements on trapped antihydrogen have achieved relative precisions of parts per trillion. However, the ground-state hyperfine splitting, which is sensitive to the internal structure of the antiproton, has only been measured to 400 parts per million (ppm). Here we report a 4 ppm measurement of the antihydrogen ground-state hyperfine splitting energy a1S, advancing the state-of-the-art precision by two orders of magnitude. From microwave spectroscopy experiments with roughly 24,000 anti-atoms, we determine in a 1-T magnetic field, consistent with expectations for hydrogen. At this level, our measurement is sensitive to the internal structure of the antiproton, which contributes at about 40 ppm and is approaching the limit of existing theoretical analyses. The gains we report are the product of marked advances in magnetic trap field control, stabilization and characterization; anti-atom spin-state manipulation; and improved antihydrogen accumulation rate.
published_date 2026-05-28T08:02:06Z
_version_ 1866958243200237568
score 11.106877

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