Breaking the tiny bounds of quantum mechanics, researchers at the Southern University of Science and Technology and the Quantum Science Center of the Guangdong–Hong Kong–Macao Greater Bay Area have created a massive Schrödinger cat particle under ultracold conditions, reaching nearly absolute zero.
In quantum mechanics, particles can exist in a superposition of uncertainty, only existing in a certain position once they are measured, most famously illustrated by Schrödinger’s cat, an example in which the condition of a cat inside a box cannot be known until opening it.
Now, in a recent paper published in Nature Physics, the team revealed how they developed a seven-atom cluster that, when passing through a barrier higher than its own kinetic energy, entered a superposition state on a new scale.
Quantum Superposition
When an object enters a quantum superposition, it theoretically occupies multiple points of space at once, with its precise location unsure until measurement occurs. Typically, this is relegated to extremely tiny sub-atomic systems. Yet in their new research, the Hong Kong and Chinese team produced quantum tunneling in a larger system, which could be a major boon to the development of quantum sensors at a larger scale.
In addition to spatial quantum superposition, the team identified quantum tunneling as the other core concept in their recent work. A particle’s ability to quantum tunnel, which references its ability to cross a solid or energy barrier that would typically be impenetrable based on classical physics, declines with mass.
The researchers wondered whether there was a way around this, allowing macroscopic objects to undergo quantum tunneling. Typically, quantum tunneling occurs at the subatomic scale, perhaps a single atom at most, yet the team sought to move several atoms joined together through a quantum tunnel in their new work.
Quantum Activity at Large Scale
For their large-scale quantum tunneler, the team built a mass system on an optical lattice by cooling the atoms to near absolute zero and trapping them with laser beams. Many quantum technologies, such as quantum computers, require extremely low temperatures, as cooling atoms to this degree enhances their quantum properties.
While the added mass complicates quantum tunneling due to inefficiency, creating a superposition in such a relatively large object could have fascinating repercussions for fundamental physics, especially in the poorly understood relationship of quantum mechanics and gravity.
The key to the team’s success was using a relatively weak bond between atoms rather than the tighter bonds typically used, allowing them to exploit the object to achieve a tunneling strength closer to that of a single atom.
With this new method, the team has developed a highly scalable process that is theoretically capable of achieving the same results with about 100 atoms. Further work to confirm their results could lead to the generation and detection of even larger spatial quantum superpositions.
Future Applications
The work may enable future researchers to investigate quantum effects at even larger scales and facilitate the development of quantum sensors and measurement devices. Additionally, atomic interferometry, which measures motion, gravity, time, and more based on the atom’s wave-like behaviors, could benefit from the technique by pushing it past the normal quantum limit.
This could be especially useful in investigating the weak relationship between gravity and mass, which is hard to detect at very small scales.
In the near future, the researchers have identified specific elements of their work that they will continue to pursue. Their success with the experiment also enabled the team to observe peculiar quantum phenomena, such as long-lived, strongly interacting states and many-body interactions, which they hope to investigate further.
Moving forward, they also aim to push beyond the current theoretical limit of 100 atoms in their work to several hundred atoms.
The paper, “Scalable Generation of Massive Schrödinger Cat States Via Quantum Tunnelling,” appeared in Nature Physics on May 11, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.