Measuring Quantum Cats and Their Smiles

By Shawn Radcliffe

creatticacatIt’s been a strange summer for quantum physics, but when it comes to this unusual branch of science, strange is actually a sign of progress.

In a study published July 31 in Nature, researchers from the University of California, Berkeley, carried out an experiment involving a quantum circuit. Using special techniques, they were able to monitor the shift of this system from a quantum to a classical state in order to determine the most likely path that it would follow.

Quantum systems are those that exist in multiple states at one time—until the system is measured. This is based on Schrodinger’s cat, a thought experiment in which a cat inside a closed box with a vial of poison exists in two states at the same time—alive and dead—until the box is opened (aka measured).

The researchers found that by gently monitoring a quantum system, without causing it to collapse into a definite state, scientists might one day be able to nudge a system—such as a chemical reaction—in one direction or the other, even if it’s not the most likely outcome.

The second study involved a different kind of feline—the quantum Cheshire cat, named after the curious creature from Alice in Wonderland whose smile lingered long after the rest of the body had faded.

Researchers from the Vienna University of Technology, in a study published July 29 in Nature Communications, showed that it was possible to separate a neutron from one of its physical properties—the magnetic moment, which describes how the neutron interacts with an external magnetic field.

Using a technique called interferometry, the researchers split a beam of neutrons into two streams, each with a different spin for the magnetic moment. Using quantum filters and special detection equipment, the researchers found that the system acted as if the neutrons moved along one path, while the magnetic moment traveled along another—essentially separating the Cheshire cat from its smile.

While the neutrons didn’t really lose their magnetic moment, this curious experiment suggests that scientists might be able to separate a quantum system from one of its properties. This could come in handy if that property is interfering with the measurement of another one—in the same way that it’s difficult to look at a cat that’s smiling at you. This experiment reminds us of what sages have been pointing to, that there is no experiencer and no experience, but only experiencing. As Krishnamurti wrote in “The First and Last Freedom”:

“You can experiment with this for yourself very simply and very easily. Next time you are angry or jealous or greedy or violent or whatever it may be, watch yourself. In that state, “you” are not. There is only that state of being. The moment, the second afterwards, you term it, you name it, you call it jealousy, anger, greed; so you have created immediately the observer and the observed, the experiencer and the experienced. When there is the experiencer and the experienced, then the experiencer tries to modify the experience, change it, remember things about it and so on, and therefore maintains the division between himself and the experienced. If you don’t name that feeling—which means you are not seeking a result, you are not condemning, you are merely silently aware of the feeling—then you will see that in that state of feeling, of experiencing, there is no observer and no observed, because the observer and the observed are a joint phenomenon and so there is only experiencing.”

Continue reading

Related Content