Scientists have achieved a new level of control over molecules as they were able to manipulate a calcium monohydride molecular ion — made up of one atom of hydrogen and one atom of calcium. This feat, achieved by physicists at the National Institute of Standards and Technology (NIST), opens possibilities for quantum technology, chemical research and exploring new physics.
To control a particle, we need to pinpoint it in one specific state. A molecule has a large number of states it can be in because of its rotation and vibration, said Dalton Chaffee, lead author on the paper. This, in essence, is what makes molecules so much harder to control than atoms. Team used a technique called quantum logic spectroscopy To gain this control, the team used a technique called quantum logic spectroscopy, first developed to increase the precision and accuracy of clocks made of electrically charged aluminum atoms (ions).
To communicate with their molecular ion, the researchers used a calcium ion as a helper. They trapped the calcium helper ion and the charged calcium monohydride molecule together, and since they are equally charged, they naturally repel each other.
Think of them as if they were pushed apart by a loaded spring between them, according to a press release.The team highlighted that the calcium monohydride doesn’t interact well with the laser, but the solo calcium ion does. Using lasers, the researchers cool the calcium ion, slowing its motion. As the calcium slows its momentum, its molecule friend slows too. Cooling the molecule is critical, graduate student April Sheffield pointed out.
And in addition to laser cooling, a cold environment allows scientists to hold the molecular state unchanged for 10 times longer than they could at room temperatures. Molecule can remain in its rotational state for around 18 seconds Then the researchers shine a laser on the molecule to change its rotation. They can’t tell if the molecule is rotating, but the calcium ion can. When the molecule changes rotation, the helper calcium ion picks up on it and releases a tiny flash of photons, which researchers see as a bright dot.
They tell the molecule to change the rotation back, and the calcium ion flashes again, according to the study. That double flash of the calcium ion signals two quantum leaps, or two jumps between two different states of the molecule. Seeing that level of quantum control in action is satisfying as a scientist, said NIST postdoctoral fellow Baruch Margulis. That s quantum mechanics.
In our lab, we can see with the camera if our ion is in one quantum state or another, which I find super cool, he said. It’s captivating to see it with your own eyes. The research team also revealed that the molecule can remain in its rotational state for around 18 seconds before the surrounding thermal radiation forces the molecule to change its state and the ion stops flashing.
That’s one of the main results of their study. Those 18 seconds are important because it gives the researchers thousands of opportunities to measure the molecule’s state before it changes. It s sort of a peekaboo game, if you wish, Margulis explained. As soon as thermal radiation drives the molecule to a different state, the flashes of light from the observer ion cease, and we’re able to see that almost as it happens, within 10 milliseconds or so.
One peek at the ion isn’t enough; scientists checked repeatedly if the calcium ion was bright or dark, proving that they had control over the molecule’s state and the result wasn’t a fluke. The team achieved a 99.8% success rate, meaning that if they made 1,000 attempts to manipulate the molecule, they were successful about 998 times. This method could allow scientists to use a wide range of molecules for specific quantum tasks, explore physics beyond the Standard Model and potentially control chemical reactions.
Molecules can serve as versatile building blocks for quantum technologies, but they are much harder to control than atoms.
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