It’s a long way from “beam me up, Scotty" and not quite Schrodinger’s tardigrade, but for the first time, a living animal has been claimed to be quantum entangled – and lived. Once thought of as confined to the world of subatomic particles, quantum entanglement has slowly been applied to more and more complex objects, now possibly including a multi-cellular life form for the first time. However, some physicists dispute what occurred was real entanglement.
Quantum entanglement is a process so mind-bendingly strange Einstein famously refused to accept it could be true. Entangled particles’ states are bound to each other so that, even at a distance, a change to one’s spin, momentum, or polarization causes an instant change to another.
Science fiction writers have loved to play with creating universes where the rules of quantum behavior can be applied on a human scale, allowing phenomena such as matter transporters. Provided his claims survive peer review, Dr Rainer Dumke of the Nanyang Technological University, Singapore, has brought those dreams just a little closer, even if his entangled animal is too small to see with the naked eye. In a paper uploaded to the preprint server ArXiv.org, Dumke and co-authors describe entangling a frozen tardigrade to two electric circuits.
Dumke is a leader in the field of quantum mechanics, but he also doesn’t believe in taking it too seriously, as evidenced by his team’s homepage being called qauntumshmantum. In 2019 he shared an IgNobel Prize, the ultimate reward for a scientist with a sense of humor, for showing magnetic deposits behave differently in living and dead cockroaches.
Tardigrades, also known as water bears and moss pigs, are microscopic creatures uniquely suited to such research. Not only are they smaller than some bacteria, but they can suspend their living functions, allowing them to be boiled, frozen, exposed to total vacuums or unimaginable amounts of pressure and recover.
The paper notes that Niels Bohr claimed it was impossible to study the chemistry and organizational hierarchy of a living cell simultaneously, and drew an analogy with the limitations imposed by Heisenberg’s Uncertainty Principle on studying atoms. However, Dumke and co-authors argue, Bohr did not allow for tardigrade’s state of suspended animation in which “it is possible to do a quantum and hence a chemical study of a system, without destroying its ability to function biologically.”
The team proved this using a species of tardigrades, Ramazzottius varieornatus – 0.2-0.45 mm (0.008-0.018 inches) – collected from a roof gutter in Denmark and frozen. This caused the tardigrades to enter a desiccated state called a tun where they turn off their living functions and shrink to a third of their length. Three tuns were further cooled to 0.01 °C above absolute zero.
They then placed each tardigrade between shunt capacitor plates of a superconductor circuit that formed a quantum bit (qubit). Known as Qubit B, this circuit was coupled to a nearby circuit, Quibit A, so the two were entangled. Experiments then seemingly showed the tardigrade was also entangled so that any changes to the quantum states of the qubits produced changes in the tardigrade.
Seventeen days after first being exposed to such conditions, the tardigrades were warmed up and placed in room temperature water, although only one survived.
“Our work provides a first step in the exciting direction of creating hybrid systems consisting of living matter and quantum bits,” the authors conclude.
The publicity the work has attracted has meant that informal peer review has preceded the formal part, instead of the other way round as usually happens, and some reviewers are not proving kind. " It's important to point out that the authors did not entangle a tardigrade with a qubit in any meaningful sense. This is not 'quantum biology'" Professor Douglas Natelson of Rice University posted on his blog.
"The tardigrade is mostly (frozen) water, and here it acts like a dielectric, shifting the resonance frequency of the one qubit that it sat on... This is not entanglement in any meaningful sense. If it were, you could say by the same reasoning that the qubits are entangled with the macroscopic silicon chip substrate."
Others agree. So far the authors have not responded, so it is possible their only achievement is reviving a tardigrade after being cooled to an unprecedented temperature.
Still, efforts to build matter transporters have to start somewhere. And since humans (or cats) are not capable of putting ourselves in states of suspended animation, it’s unlikely we will be entangling ourselves any time soon.
Meanwhile, one more reason to be a water bear.
[H/T: New Scientist]