Scientists Created an Antimatter Qubit That Could Upend Physics

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Here’s what you’ll learn when you read this story:

The explanation behind the universe’s matter-antimatter asymmetry—an apparent violation of a fundamental law of nature known as charge-parity-time (CPT) symmetry—is one of particle physics’ greatest mysteries.
A new study details how scientists at CERN created antimatter qubits, which could improve physicists investigations into magnetic moment differences between matter and antimatter.
This breakthrough—along with CERN’s ongoing effort to protect the transport of particles to other laboratories—could drastically improve baryonic antimatter research.

The universe is filled with something instead of nothing—and that’s a problem. Well, a quick clarification: This unexplainable quirk of science is great news for you, me, and every other living being throughout the cosmos, since it means that we (being made of matter) get to exist. But from a particle physicist’s perspective, it represents a massive gap of knowledge in the Standard Model, which is our current best guess at explaining the strange world of the subatomic.

The Swiss-based particle physics laboratory CERN, home of the Large Hadron Collider, is at the forefront of exploring this particular unknown, which is an apparent violation of a fundamental law of nature known as charge-parity-time (CPT) symmetry. This nearly 75-year-old theory posits that matter and antimatter behave identically, meaning that they should have annihilated each other mere moments after the Big Bang. But for some reason, matter prevailed.

Now, a recent study—led by scientists at CERN and published in the journal Nature—details a new tool in their exploratory toolbox for trying to understand why the universe contains something instead of nothing. At its most basic, researchers created the world’s first antimatter “qubit”—the quantum-powered building blocks of quantum computers—in an effort to study matter-antimatter asymmetry with higher fidelity. This was achieved by the Baryon Antibaryon Symmetry Experiment (BASE) collaboration using the antimatter factory at CERN.

Like most things that deal with quantum properties, the main challenge was keeping the antiproton from experiencing decoherence, in which a qubit loses its quantum properties via disruptions from the surrounding environment. The researchers successfully kept the antiproton trapped and oscillating smoothly between quantum states for almost a minute and then measured transitions between magnetic moments using a process known as “coherent quantum transition spectroscopy.” Although an incredibly complicated process, CERN describes this method like pushing a child on a swingset:

With the right push, the swing arcs back and forth in a perfect rhythm. Now imagine that the swing is a single trapped antiproton oscillating between its spin “up” and “down” states in a smooth, controlled rhythm. The BASE collaboration has achieved this using a sophisticated system of electromagnetic traps to give an antiproton the right “push” at the right time. And since this swing has quantum properties, the antimatter spin-qubit can even point in different directions at the same time when unobserved.

This qubit isn’t destined to run in some hyper-advanced quantum computer. Instead, its role lies in exploring the very edge of the standard model of particle physics. Previously, BASE collaboration has shown that magnetic moments of protons and antiprotons are identical up to just a few parts-per-billion—any detectable deviation would violate CPT symmetry and possibly explain why protons outnumbered antiprotons following the Big Bang. However, these results used incoherent techniques impacted by magnetic field fluctuations and perturbations caused by the measurements themselves. This new technique suppresses those interferences and makes coherent observations that are many times more accurate than previous magnetic moment experiments.

“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,” BASE spokesperson Stefan Ulmer, a co-author of the study, said in a press statement. “Most importantly, it will help BASE to perform antiproton moment measurements in future experiments with 10- to 100-fold improved precision.”

And this new level of precision is only the beginning. A simultaneous effort known as BASE-STEP (Symmetry Tests in Experiments with Portable Antiprotons) utilizes a portable trap system so antiprotons can be transported to other facilities with more stable environments. In October of last year, BASE-STEP successfully transported 70 protons via truck on a round trip at CERN’s main site. This will allow labs throughout Europe—and maybe, one day, the world—to work on one of physics’ most puzzling mysteries.

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