Ever since Paul Dirac theoretically predicted antimatter, physicists have been hunting for the tiniest differences between particles and their antiparticles. A new approach suggests staging a musical duet: a laser, acting like a bow, will make a molecular string of ordinary hydrogen and an identical string of antihydrogen resonate, then compare the pitch.
The objects are the hydrogen molecular ion H₂⁺ (two protons, one electron) and its anti-twin H̄₂⁻ (two antiprotons, a positron). These ions will float in a magnetic trap, and ultra-sensitive spectroscopy (a method of measuring light absorption) will capture their vibrations. According to the Standard Model (our best theory of elementary particles), the frequencies should match perfectly.
The big surprise: the anti-molecule H̄₂⁻ has never been created. Experimentalists will literally have to assemble it atom by atom from antiprotons and positrons trapped in a cage. But the achievable measurement precision is such that it would detect a disharmony equivalent to a single false note in a symphony of ten quadrillion sounds.
These molecular strings vibrate at hundreds of trillions of oscillations per second — far above any note audible to the human ear, but laser detectors easily tell them apart.
If in 'Angels and Demons' antimatter was a bomb, for physicists it's the perfect tuning fork to check the harmony of nature's laws.