Scientists used an artificial atom to show the possibility of keeping Schrödinger's cat alive for an indefinite period, as well as accelerating the onset of its demise. For this and that, you don't even need to look into the box in which this very cat usually sits (or does not sit). Using classical analogies like this may seem oversimplified or odd, but for science it is very important. They show how reality is found at a fundamental level and can lead to better tools that physicists use in quantum engineering.
Scientists at the University of Washington in St. Louis decided to find out for sure whether it was necessary to collect information from a quantum system at all - or, more simply, look at a particle - to influence its behavior. Maybe "braking" will be enough?
Spoiler alert: They've figured out there is no need to watch.
A bit of history: the cat, the box and Zeno's effects
If anyone does not know what kind of Schrödinger's cat, we recall the legend. According to the Copenhagen interpretation of quantum mechanics, a physical object (like an atom) has no specific properties until we measure it. In response, physicist Erwin Schrödinger proposed a thought experiment. He suggested that if this interpretation is correct, we could put the radioactive substance in a small container next to the Geiger counter, tie the counter to a hammer, and place the hammer over the acid capsule so that it crushes it as the atom decays.
If we put all this in a box with a cat, we will not be able to measure the properties of the atom, because, as far as we know, the atom simultaneously decayed and did not decay (that's why it has a half-life). As a consequence, the cat will be both alive and dead at the same time, until we look inside.
This is the legend. But she has a double bottom.
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In 1974, scientists asked the question: Does the lifetime of an unstable system depend on a measuring device?
This paradox has come to be known as the quantum Zeno effect: What happens if we continuously observe an unstable atom? Will it disintegrate?
According to the Zeno effect, under constant observation, it will never emit a single particle of radiation. In 1989, this was first demonstrated in an experiment by the US National Institute of Standards and Technology, and a strange hypothesis became a strange reality.
Ten years later, the opposite Zeno effect was proposed - the Antisenon effect. Frequent measurement of a radioactive atomic nucleus can accelerate its decay, depending on the process.
It remains only to understand what a "dimension" is.
To measure something like a radioactive atom, to observe over it and read its parameters and properties, you need to somehow interact with it so that the information comes out in some form. In the process, the many possibilities of the atom collapse into a single outcome, which we see. But is this collapse the cause of the Zeno effect? Or is it possible to accelerate or slow down the decay of an atom without leading to its collapse into an absolute state?
Zeno vs. Antisenon
All this brings us back to an experiment conducted by the University of Washington.
To determine whether the transmission of information would force the Zeno or Antiseno effect, scientists used a device that in many ways behaves like an atom with many energy states.
This "artificial atom" was able to test the hypothesis of how energy states - electromagnetic modes - might influence these effects.
"The rate of atomic decay depends on the density of possible energy states, or electromagnetic modes, for a given energy," says researcher Keiter Merch. “For an atom to decay, it must emit a photon in one of these modes. More mods means more ways of decay, so faster decay”.
Likewise, fewer mods means fewer options for decay, which explains why an atomic pot under constant supervision will never weld. Merch and his team were able to manipulate the number of modes in their artificial atom before using standard measurements, checking its state every microsecond and speeding up or slowing down its "decay".
"These measurements represent the first observation of two Zeno effects in a unified quantum system," says Merch.
To make sure that it was observation or interference that turned out to be key, scientists made a so-called quasi-measurement, which creates interference without leading to the collapse of the atomic state. Nobody knew what the result would be.
“But data collected all day long consistently showed that quasi-measurements produced Zeno effects in the same way as conventional measurements,” says Merch.
Consequently, it is the violation in the measurement process, and not the direct measurement itself, that leads to the appearance of the Zeno and Antiseno effects.
Knowing this, we can apply new methods of controlling quantum systems using Zeno dynamics.
What does all this mean for poor Schrödinger's cat?
“The Zeno effect says that if we test the cat, we will reset the decay clock and save the life of the cat,” says scientist Patrick Harrington. “But the trick is that Zeno's effects are about violation, not information, so you don't even need to look into the box to trigger them. The same effects will take place if you just shake the box."
ILYA KHEL