Physicists design a way to detect quantum behavior in objects as large as ours: ScienceAlert
Quantum science is usually concerned with very small scales, where the mathematics of probability becomes a more useful tool than “classical” descriptions of matter. Now, new research has come up with a way to measure the amount of much larger masses.
Scientists have wanted to test the quantum nature of larger objects for a long time: the general consensus is that quantum physics applies at every scale, but as objects grow in mass and complexity, their quantity becomes harder to observe.
Now, a team from University College London (UCL), the University of Southampton in the UK, and the Bose Institute in India, has come up with an approach to quantum measurement that can theoretically be applied to something regardless of its mass or energy. .
“Our proposed experiment could test whether an object is classical or quantum by seeing whether the act of observation can lead to a change in its motion,” says physicist Debarshi Das of the University of California, California.
Quantum physics describes a universe where things are not defined by a single measurement, but as a set of possibilities. An electron can spin up and down, or has a greater chance of being in some regions than others, for example.
In theory, this is not limited to the little things. In fact, your body could be described as having a very high probability of sitting in that chair and a very (very!) low probability of being on the moon.
There’s only one basic fact to remember – if you touched it, you bought it. Observing the quantum state of an object, whether it is an electron or a person sitting in a chair, requires interactions with a measurement system, forcing it to make a single measurement.
There are ways to pick things up while keeping their sleeve down, but they require keeping the body in a terrestrial state — very cold, very still, and completely cut off from its environment.
This is difficult for individual molecules, and becomes more difficult as the scale size increases. The new proposal uses a completely new approach, one that uses a set of assertions known as the Leggett-Garg inequality and non-signality in time conditions.
In fact, these two concepts describe a familiar universe, where a person is sitting in a chair there even if the room is dark and you can’t see him. Suddenly turning on the light won’t reveal that they’re actually under the bed.
If an experiment finds evidence that somehow contradicts these assertions, we might be able to glimpse quantum mystery more broadly.
The team suggests that objects could be observed swinging on a pendulum, like a ball on the end of a piece of string.
The light on the two halves of the experimental setup would then be flashed at different times — counted as an observation — and the results of the second flash would indicate whether quantum behavior was occurring, because the first flash would affect whatever was moving.
We’re still talking about a complex setup that would require some sophisticated equipment, and ground-like conditions, but through the use of motion and two measurements (blips), some of the limitations on mass are removed.
“The crowd at a football match cannot influence the outcome of the match just by staring hard,” says Das. “But in quantum mechanics, the process of observation or measurement itself changes the system.”
The next step is to try this proposed setup in an actual experiment. Mirrors at the Laser Gravitational-Wave Observatory (LIGO) in the United States have already been suggested as suitable candidates for examination.
These mirrors act as a single object weighing 10 kilograms (22 pounds), a step above the typical size of objects analyzed for quantum effects, which amounts to about a quintillionth of a gram.
“Our scheme has broad conceptual implications,” says physicist Sugato Bose of the University of California, Los Angeles. “It could expand the field of quantum mechanics and explore whether this fundamental theory of nature is valid only at certain levels or if it is true for larger masses as well.”
The research was published in Physical review letters.