Quantum Entanglement Has Been Directly Observed on a Macroscopic Scale

This is what physics is all about.
Brad Bergan
A digital cluster of intersecting planes.Lan Zhang / iStock

Quantum entanglement is the "spooky action at a distance" where two particles or objects seem to affect one another regardless of range, ostensibly breaking the laws of classical physics. But the weirdness is far outweighed by the intrigue scientists experience, which has led to a group of researchers directly observing and recording quantum entanglement at the macroscopic scale for the first time ever, according to a recent study published in the journal Science.

For macroscopic objects, quantum entanglement can still reign

While the new direct observation happened on a macro scale, the recent experiment is still very small from our human perspective, and involved two tiny aluminum drums only one-fifth the width of a human hair -- impractically small for humans, but unspeakably colossal on the quantum scale. "If you analyze the position and momentum data for the two drums independently, they each simply look hot," said John Teufel, a physicist of the National Institute of Standards and Technology (NIST), in the U.S., in a Science Alert report. "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."

Evidence is scarce on whether quantum entanglement can happen with macroscopic objects, and until the recent experiment, it was thought that we couldn't observe them at larger scales, where physical objects are firmly governed by forces of the larger, life-dwelling level of the universe. Not so, according to the recent research, which shows the same quantum rules also apply on the macro scale. The scientists used microwave photons to vibrate tiny drum membranes, and kept their positions and velocities in a synchronized state.

Bypassing Heisenberg's Uncertainty Principle

To maintain the boundary between the drums and external forces (which often interferes with quantum states), the drums were cooled, entangled, and finally measured in separate stages from within a contained and cryogenically chilled space. The drum states were then encoded in a reflected microwave field, which performs a lot like radar. Earlier studies also hinted at macroscopic quantum entanglement, but the novel research takes things to another level: Every sought measurement in the experiment was recorded directly, instead of merely indirectly inferred, and the entanglement was produced in a deterministic way, more favorable to the notion in classical physics of a machanistic universe.

A related but separate series of experiments saw researchers work with macroscopic drums (also called oscillators) in a state of quantum entanglement, which showed how scientists may measure the position and momentum of the two drumheads simultaneously. "In our work, the drumheads exhibit a collective quantum motion," said Laure Mercier de Lépinay of the Finland-based Aalto University, in the Science Alert report. "In this situation, the quantum uncertainty of the drums' motion is canceled if the two drums are treated as one quantum-mechanical entity."

Central to this breakthrough is the bypassing of Heisenberg's Uncertainty Principle, which holds that no one can measure to perfection position and momentum at the same time. Recording either will interfere with the other, according to the principle, in a reaction called quantum back action. Needless to say, this recent experiment is a huge deal, and could lead to future applications where both sets of data are knowable in quantum networks, allowing the manipulation and entanglement of macro-scale objects, potentially powering the next generation of advanced communication networks.

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