A bizarre discovery has revealed that cold helium atoms in lab conditions on Earth abide by the same law of entropy that governs the behaviour of black holes. Read more: What are black holes? WIRED explains
The law, first developed by Professor Stephen Hawking and Jacob Bekenstein in the 1970s, describes how the entropy, or the amount of disorder, increases in a black hole when matter falls into it. In particular, it explains that entropy only increases when the surface area of the black hole changes, not the volume. It is like measuring how many files there are in a filing cabinet based on the surface area of the drawer, rather than how deep the drawer is.
Another way of looking at entropy is this: an egg in its 'classic' state has low entropy, while a whisked egg has high entropy. You can't reverse this process meaning entropy, like time, only moved forward.
Hawking and Bekenstein proposed that when matter gets too close to the event horizon of a black hole and ultimately gets pulled in, the information contained in that matter is added to the black hole and this is a form of entropy. As the black hole's surface area increases, so too does its event horizon, which increases the amount of matter than can be pulled in and entropy hurtles on.
Now, it seems, this behaviour appears at both the huge scales of outer space and at the tiny scale of atoms, specifically those that make up superfluid helium.
"It's called an entanglement area law,” explained Adrian Del Maestro, physicist at the University of Vermont. "It points to a deeper understanding of reality” and could be a significant step toward a long-sought quantum theory of gravity and new advances in quantum computing.
The law works because of a quantum mechanical property called entanglement. When atoms are 'entangled' the measurement of one of the atoms will not only cause it to 'pick' one state, but it will also instantaneously cause the atoms it is entangled with to do the same, even if that atom has not been measured itself.
Using two supercomputers, Del Maestro and his team studied interactions of 64 helium atoms in a superfluid, which is a fluid with zero viscosity.
The researchers found the amount of entangled quantum information shared between two regions of a container was determined by the surface area of the sphere, not its volume. They also found the degree of entanglement in the superfluid depended on its density.
"Entanglement is non-classical information shared between parts of a quantum state," notes Del Maestro. It's "the characteristic trait of quantum mechanics that is most foreign to our classical reality."
Read more: Quantum computing and quantum supremacy, explained
The idea had been considered but never been seen. Now it has been witnessed, it could become useful in trying to build quantum computers, which rely on entanglement to function. Due to the way the tiniest of particles behave, operations can be done much more quickly and use less energy than classical computers.
In classical computing, a bit is a single piece of information that can exist in two states – 1 or 0. Quantum computing uses quantum bits, or 'qubits', with two states that store much more information than just 1 or 0, because they can exist in any superposition of these values. Put more simply, think of a qubit like a sphere. A classical bit would sit at either of the poles of this sphere, but a qubit can sit at any point on the sphere.
"Traditionally qubits are treated as separated physical objects with two possible distinguishable states, 0 and 1," Alexey Fedorov, physicist at the Moscow Institute of Physics and Technology told WIRED. "The difference between classical bits and qubits is that we can also prepare qubits in a quantum superposition of 0 and 1 and create nontrivial correlated states of a number of qubits, so-called 'entangled states.'"
"Superfluid helium could become an important resource – the fuel – for a new generation of quantum computers," said Del Maestro. To make use of its information processing potential, however, "we have to understand more deeply how it works" he added.
This article was originally published by WIRED UK
