Is gravity a quantum phenomenon? This has been one of the major open
problems in physics for decades. Along with a British colleague, Anupam
Masudar, a physicist at the University of Groningen, proposed an experiment
that could solve the problem. However, we need to study two very large
entangled quantum systems in free fall. In a new treatise, headed by a
third-year bachelor’s degree, Mazumdar shows how to reduce background noise
to make this experiment more manageable.
Three of the four fundamental forces in physics can be explained in terms of
quantum theory. This does not apply to the fourth force (gravity) explained
by Einstein’s general theory of relativity. Experiments previously designed
by Masudar and his colleagues may prove or disprove the quantum nature of
gravity.
Superposition
A well-known result of quantum theory is a phenomenon called quantum
superposition. In certain situations, a quantum state can have two different
values at the same time. Takes the electrons irradiated by the laser beam.
According to quantum theory, photon energy from light can be absorbed or not
absorbed. When it absorbs energy, the spin of the electron changes. This can
cause the magnetic moment to go up and down. As a result of quantum
superposition, the spin is both up and down.
These quantum effects occur in small objects such as electrons. By targeting
the electrons of a specially constructed miniature diamond, you can create
superpositions on much larger objects. The diamond is not only small enough
to maintain this superposition, but large enough to feel gravity. This
property is used by experiments. Two of these diamonds are placed next to
each other in free fall, thus offsetting external gravity. This means that
they interact only through the gravity between them.
Challenging
And then another quantum phenomenon occurs. Entanglement means that when two
or more particles are generated in close proximity, their quantum states are
linked. For diamonds, if one is spinning up, the other intertwined diamond
must spin down. Therefore, the experiments are designed to determine if
entanglement occurs in pairs during free fall when gravity between diamonds
is the only way to interact.
“But this experiment is very challenging,” explains Mazdal. When two objects
are very close together, there is another possible mechanism of interaction,
the Casimir effect. In a vacuum, this effect allows two objects to attract
each other. “The size of the effect is relatively large and you need to use
a relatively large diamond to overcome the noise it produces.” The first
thing you need to do to reduce this noise is to make your experiment easier
to handle. It was clear from. Therefore, Masudar wanted to know if it was
possible to shield the Casimir effect.
Blockade
He passed this question on to Thomas van de Kamp, a third-year physics
student. “He came to me because he was interested in quantum gravity and
wanted to do a bachelor’s thesis research project,” says Mazdal. Van de Camp
began to tackle the problem when most regular classes were interrupted
during the spring blockade. “In a very short time, he presented his solution
as described in our treatise.”
This solution is based on placing a copper conductive plate about 1 mm thick
between two diamonds. The plate shields the Kashmir potential between them.
Without the plate, this possibility brings the diamonds closer together. But
with plates, the diamonds are not attracted to each other, but to the plates
between them. Mazdal: “This removes a lot of noise from the experiment
because the Casimir effect removes the interaction between the diamonds.”
Notable
Calculations performed by Van de Kamp show that the mass of two diamonds can
be reduced by two orders of magnitude. “It may seem like a small step, but
it makes the experiment less demanding.” In addition, other parameters such
as the level of vacuum required during the experiment are also less
demanding due to the Casimir effect shield. Become. Mazumdar states that
further updates to the experiment may occur in the near future, including a
contribution from a bachelor’s degree student, Thomas van de Kamp. “So his
six-month project brought him the co-authorship of two treatises. This is a
very amazing achievement.”
Reference:
Thomas W. van de Kamp et al, Quantum gravity witness via entanglement of
masses: Casimir screening, Physical Review A (2020). DOI:
10.1103/PhysRevA.102.062807
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