Tardigrades become the first animals to achieve quantum entanglement?

Tardigrades become the first animals to achieve quantum entanglement?

01

It has always been difficult to discuss biological and quantum systems together because they seem to require opposite conditions: Life is complex and "hot and wet," while quantum objects are small, cold, and need to be precisely controlled.

However, in a new study, a team of physicists conducted a quantum entanglement experiment using tardigrades, also known as water bears.

The tardigrade, which has the title of the strongest creature on earth, is a tiny multicellular organism.

When these amazing tiny creatures accidentally landed on the moon in 2019, it sparked concerns that the lunar surface might be contaminated.

In laboratories on Earth, they have also "participated" in a number of scientific studies. For example, they have been hit by ultra-high-speed bullets, bathed in boiling hot water, exposed to strong ultraviolet radiation, and lived in a vacuum environment...

All of these extreme conditions are designed to test a state called "tun," which is a tardigrade's extreme survival mechanism.

In this state, they curl up into a shrunken, dehydrated ball and their metabolic levels can drop to as low as 0.1% of normal, suspending their biological functions indefinitely.

Now, the researchers have posted details of their experiment on the preprint site arXiv, in a new paper they say shows that tardigrades can achieve temporary quantum entanglement.

If the research passes peer review, the experiment would confirm that tardigrades are the first living animals to become entangled.

02

Quantum entanglement is a strange phenomenon in quantum mechanics that usually occurs at the subatomic particle scale.

Two entangled particles are mysteriously "connected" together in some way. When the properties of one particle change, the other particle will instantly change in the same way. This connection can still exist even if one of them is located on Earth and the other is in a distant galaxy outside.

Einstein once expressed doubts about this phenomenon and called it "spooky action at a distance."

But the effect can extend beyond the realm of subatomic particles. In a 2018 study published in the Journal of Physical Communications, a team of researchers showed that certain kinds of light and bacteria can become entangled with photons.

So, can tardigrades, as multicellular organisms, also develop this strange connection?

In the new study, the team of researchers collected three tardigrades from a roof gutter in Denmark. In their dynamic state, their size ranged from 0.2 to 0.34 mm, but when the researchers froze them and put them into the "tun" state, their size shrank to about one-third of their original size.

The researchers then froze the tardigrades a step further, cooling them to very close to absolute zero (10mK) and placing them under very low pressure.

In the experiment, the researchers placed the tardigrade in the "tun" state between two capacitor plates of a superconductor circuit, which can form a quantum bit. As shown in the figure below, quantum bit B is coupled to its nearby quantum bit A through a capacitor.

When the tardigrade comes into contact with qubit B, it changes the resonant frequency of qubit B.

Then, the combination of the tardigrade and qubit B will be coupled to qubit A, making the two systems entangled with each other.

Circuit diagram of two qubits and a tardigrade (T). | Image reference: KSLee et. al. / arXiv

In several tests, the researchers found that the frequencies of both the qubit and the tardigrade changed in tandem, like a three-part entangled system.

After the three tardigrades had been in the "tun" state for 420 hours (17.5 days), the researchers gently heated them in an attempt to revive them.

As a result, one tardigrade returned to its active state, while the other two died. Researchers believe that this sole survivor is the first quantum entangled animal in history.

03

This result undoubtedly sounds exciting. However, once this new study, which has not yet been peer-reviewed, was published, it received a lot of criticism and doubts from the scientific community.

One of the main controversies is that the coupling observed in the experiment can be observed both with and without entanglement.

Physicists who support this claim argue that placing a tardigrade on a qubit might indeed change the frequency of that qubit, but that is different from entangled the two.

All the experiment did was place a tardigrade on the capacitor part of one of the two coupled quantum bits. At this time, the tardigrade is basically just frozen water. It acts like a dielectric in the experiment, changing the resonant frequency of the quantum bit it is in, which cannot be called entanglement.

Placing a tardigrade next to a quantum bit made of a circuit, or a speck of dust next to it, can produce a similar effect.

In short, critics’ claims that the tardigrades were entangled with a pair of qubits are simply wrong; the experiment did not entangle the tardigrades with qubits in any sense.

Whether the tardigrade is the first living animal to achieve entanglement may still require further exploration by scientists.

From another perspective, regardless of whether these tardigrades experienced "ghostly action at a distance", the fact that they still revived after being cooled to 10mK shows us that they are more durable than we previously thought. Even if they are not "quantum", they are already amazing enough.

Source: Principle (ID: principia1687)

Author: Xiaoyu

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