Australasian Science: Australia's authority on science since 1938

Einstein’s “Spooky Action” Goes Massive

The elusive phenomenon of quantum entanglement has been extended to the macroscopic scale after two vibrating drumheads, each the width of a human hair, displayed the “spooky action at a distance” that famously troubled Einstein.

The discovery, published in Nature (https://goo.gl/HP7g8w), opens the door to the future demonstration of teleportation between massive objects and the study of the poorly understood interplay between quantum mechanics and gravity.

Entanglement, where two distant objects become intertwined in a manner that defies both classical physics and a “common sense” understanding of reality, is perhaps one of the strangest phenomena of quantum theory. In 1935, Einstein expressed his concern over this concept, referring to it as a “spooky action at a distance”.

Nonetheless, entanglement is now considered a cornerstone of quantum mechanics, and is the key resource behind a host of potentially transformative quantum communication and computation technologies. It is, however, extremely fragile, and has previously only been observed with microscopic systems such as light or atoms, and more recently with electrical circuits.

In 2014, Dr Matt Woolley of UNSW Canberra showed theoretically that entanglement of the motion of massive objects could be prepared and detected in a superconducting electrical circuit incorporating two vibrating drumheads as the massive objects. He has now collaborated with Prof Mika Sillanpää of Aalto University in Finland to realise this vision.

The experiment was realised by precisely fabricating a superconducting electrical circuit, cooling it to just above absolute zero (–273°C), and then carefully controlling and measuring it using weak microwave fields.

The measurements demonstrate that control over massive mechanical objects is now at the level where exotic quantum states can be generated and stabilised. This opens the door to new kinds of quantum sensing, communication and computation technologies, but could also enable studies of fundamental physics, such as the poorly understood interplay of gravity and quantum mechanics.

“The next step is to demonstrate teleportation of the mechanical vibrations,” Woolley says.