When two particles or things are
entangled, even though they may be far away, their individual properties are
linked in a way that is not permitted by the laws of conventional physics.
It's an odd phenomenon that Einstein
called "spooky activity at a distance," but scientists find it
fascinating because of how odd it is. A scale much larger than the subatomic
particles typically associated with entanglement was used in a 2021 study to
directly see and record quantum entanglement.
Although the experiments used two
extremely small metal drums that were each one-fifth the width of a human hair,
the dimensions involved are still quite modest from our point of view, but they
are incredibly enormous in the world of quantum physics.
If you examine the position and
momentum data for the two drums separately, they each just seem hot, according
to physicist John Teufel of the National Institute of Standards and Technology
(NIST) in the US last year.
However, when we combine them, we find
that what seems to be a seemingly random motion in one drum is actually
strongly related to it in a way that can only be made possible by quantum
entanglement.
Although there is no reason to think
that macroscopic objects cannot experience quantum entanglement, it was
previously thought that these effects were only noticeable at larger scales or
that the macroscopic scale was governed by different principles.
According to recent studies, that may
not be the case. The same quantum laws actually apply and are visible in this
situation as well. Microwave photons were used to vibrate the tiny drum
membranes, which were kept in sync with respect to their positions and speeds.
The drums were cooled, entangled, and
then monitored in stages inside a cryogenically cold container to eliminate
outside interference, a common issue with quantum states. The states of the
drums are subsequently encoded in a radar-like reflected microwave field.
Macroscopic quantum entanglement
had been the subject of earlier investigations as well, but the 2021 study went
further: all necessary measurements were taken rather than assumed, and the
entanglement was created in a deterministic, non-random manner.
Researchers who are also working
with macroscopic drums (or oscillators) in a state of quantum entanglement have
demonstrated how it is possible to detect the location and momentum of the two
drumheads at the same time in a related but distinct series of experiments.
According to physicist Laure
Mercier de Lepinay of Finland's Aalto University, the drumheads in our work
exhibit a collective quantum motion. The drums vibrate at a phase that is the
opposite of one another; as a result, when one drum reaches the vibration
cycle's terminal position, the other one reaches it simultaneously.
In this case, treating the two
drums as a single quantum-mechanical entity cancels out the quantum uncertainty
of the drums' motion.
Heisenberg's Uncertainty
Principle, which holds that momentum and location cannot be precisely measured
at the same time, is avoided in this scenario, making it noteworthy. According
to the concept, recording either measurement will cause interference with the
other due to a phenomenon known as quantum back action.
This particular study makes use
of that entanglement to prevent quantum back action and supports the other
study in demonstrating macroscopic quantum entanglement, effectively drawing a
line between classical physics (where the Uncertainty Principle appears to
apply) and quantum physics (where it currently does not).
One of the potential future
applications of both sets of results is the ability to manage and entangle
objects on a macroscopic scale such that they can power next-generation
communication networks.
Apart from practical implications, these investigations address how far into the macroscopic domain experiments may extend the detection of clearly quantum processes, according to physicists Hoi-Kwan Lau and Aashish Clerk, who weren't engaged in the study. Both the first and follow-up research was published in Science.
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