Amazing stuff!
"In a breakthrough for antimatter research, the BASE collaboration at CERN has kept an antiproton—the antimatter counterpart of a proton—oscillating smoothly between two different quantum states for almost a minute while trapped. The achievement ... marks the first demonstration of an antimatter quantum bit, or qubit, and paves the way for substantially improved comparisons between the behavior of matter and antimatter. ...
The BASE experiment studies antiprotons produced at CERN’s antimatter factory by storing them in electromagnetic Penning traps and feeding them one by one into a second multi-trap system to, among other things, measure and change their spin states. Using this set-up, the BASE collaboration has previously been able to show that the magnitudes of the magnetic moments of the proton and antiproton are identical within a just few parts-per-billion. Any slight difference in their magnitudes would break charge-parity-time symmetry and point to new physics beyond the Standard Model of particle physics.
However, this previous result was based on an incoherent spectroscopy technique in which the quantum transitions were disturbed by magnetic field fluctuations and measurement interference. In a substantial upgrade of the experiment, these decoherence mechanisms were suppressed and eliminated, culminating in the first coherent spectroscopy of an antiproton spin. The BASE team has now accomplished this for a period—called spin coherence time—of 50 seconds.
“This represents the first antimatter qubit and opens up the prospect of applying the entire set of coherent spectroscopy methods to single matter and antimatter systems in precision experiments,” explains BASE spokesperson Stefan Ulmer. “Most importantly, it will help BASE to perform antiproton moment measurements in future experiments with 10- to 100-fold improved precision.” ..."
From the abstract:
"Coherent quantum transition spectroscopy is a powerful tool in metrology, quantum information processing, magnetometry and precision tests of the standard model. It was applied with great success in proton and deuteron magnetic moment measurements, which culminated in maser spectroscopy with sub-parts-per-trillion resolution and many other experiments at the forefront of physics. All of these experiments were performed on macroscopic ensembles of particles, whereas the coherent spectroscopy of a ‘free’ single nuclear spin has, to our knowledge, never been reported before.
Here we demonstrate coherent quantum transition spectroscopy of the spin of a single antiproton stored in a cryogenic Penning-trap system. We apply a multi-trap technique, detect the antiproton spin state using the continuous Stern–Gerlach effect and transport the particle to the homogeneous magnetic field of a precision trap (PT). Here we induce the coherent dynamics and analyse the result by quantum-projection measurements in the analysis trap (AT).
We observe, for the first time, Rabi oscillations of an antiproton spin and achieve in time-series measurements spin-inversion probabilities greater than 80% at spin coherence times of about 50 s. Scans of single-particle spin resonances show inversions greater than 70%, at transition linewidths 16 times narrower than in previous measurements, limited by cyclotron frequency measurement decoherence. This achievement marks a notable step towards at least tenfold improved tests of matter/antimatter symmetry using proton and antiproton magnetic moments."
Coherent spectroscopy with a single antiproton spin (open access)
Fig. 1: Experimental set-up.
No comments:
Post a Comment