Key takeaways
- Scientists have observed and recorded quantum entanglement at the macroscopic scale, using tiny metal drums, significantly larger than the typical subatomic particles involved in such phenomena.
- The experiments involved two metal drums, each one-fifth the diameter of a human hair, whose positions and momenta were highly correlated in a manner only explainable by quantum entanglement.
- The drums were vibrated using microwave photons and kept in synchrony within a cryogenically cold container to prevent outside interference.
- A related study showed that by treating the drums as a single quantum-mechanical entity, the quantum uncertainty of their motion could be canceled, challenging the Heisenberg Uncertainty Principle.
- These findings could pave the way for advancements in quantum networks and communications, pushing the boundaries of observing quantum phenomena in the macroscopic realm.
Quantum entanglement is the tying together of two particles or things, even if they are far away; their characteristics are connected in a way that conventional physics principles do not allow.
It’s a strange phenomena, defined by Einstein as “spooky action at a distance,” yet scientists are fascinated by it because of its strangeness. In recent study, quantum entanglement has been directly observed and recorded at the macroscopic scale, which is significantly larger than the subatomic particles typically linked with entanglement.
From our viewpoint, the dimensions are still very small – these tests employed two tiny metal drums one-fifth the diameter of a human hair – but in the domain of quantum mechanics, they are incredibly enormous.
“If you analyze the position and momentum data for the two drums independently, they each simply look hot,” explains physicist John Teufel of the National Institute of Standards and Technology (NIST) in the United States.
“But looking at them together, we can see that what looks like random motion of one drum is highly correlated with the other, in a way that is only possible through quantum entanglement.”
While there is no reason to believe that quantum entanglement cannot occur with macroscopic objects, it was previously assumed that the effects were less evident at bigger scales – or that the macroscopic scale was governed by a different set of principles.
This recent study reveals that is not the case. In reality, the same quantum principles apply and may be observed here. Researchers used microwave photons to vibrate the small drum membranes, keeping them in synchrony in terms of position and velocity.
To avoid outside interference, which is typical with quantum states, the drums were cooled, entangled, and measured in separate steps inside a cryogenically cold container. The drums’ states are then encoded in a reflected microwave field, which operates similarly to radar.
Previous studies have also reported on macroscopic quantum entanglement, but the latest study goes farther. All of the essential measurements were recorded rather than inferred, and the entanglement was created in a deterministic, non-random way.
In a related but different series of experiments, researchers working with macroscopic drums (or oscillators) in a state of quantum entanglement demonstrated how to simultaneously detect the position and momentum of two drumheads.
“In our work, the drumheads exhibit collective quantum motion,” explains physicist Laure Mercier de Lepinay of Aalto University in Finland. “The drums vibrate in an opposite phase to each other, such that when one of them is in an end position of the vibration cycle, the other is in the opposite position at the same time.”
“In this situation, the quantum uncertainty of the drums’ motion is canceled if the two drums are treated as one quantum-mechanical entity.”
What makes this big news is that it circumvents Heisenberg’s Uncertainty Principle, which states that location and momentum cannot be precisely determined at the same time. The principle states that recording either measurement will interfere with the other via a phenomenon known as quantum back action.
In addition to supporting the previous study’s demonstration of macroscopic quantum entanglement, this particular piece of research uses that entanglement to avoid quantum back action, essentially investigating the line between classical physics (where the Uncertainty Principle applies) and quantum physics (where it no longer appears to apply).
One of the potential future uses of both sets of results is in quantum networks, which enable the manipulation and entanglement of objects on a macroscopic scale to power next-generation communication networks.
“Apart from practical applications, these experiments address how far into the macroscopic realm experiments can push the observation of distinctly quantum phenomena,” write physicists Hoi-Kwan Lau and Aashish Clerk, who were not involved in the studies, in a commentary on the new findings.
