According to a study published in Nature Physics, a team led by quantum engineers from the University of New South Wales, including two University of Calgary researchers, successfully demonstrated a well-known quantum thought experiment in the real world.
Visual depiction of the atomic ‘Schrödinger cat’ state. Image Credit: University of New South Wales
It produced a “Schrödinger’s cat” within a silicon chip.
Their findings provide a novel and more robust method for quantum computations and substantial implications for error correction, which is one of the most significant barriers to developing a working quantum computer.
Scientists and philosophers have struggled to understand quantum mechanics for more than a century. The “Schrödinger’s cat” is a well-known quantum thought experiment in which a cat’s life or death is determined by the disintegration of a radioactive atom.
According to quantum mechanics, an atom must be regarded as being in a superposition—that is, existing in several states simultaneously—of decaying and not decaying unless it is directly detected. The cat is thus in a state of superposition between the dead and the living, which is a concerning conclusion.
No one has ever seen an actual cat in a state of being both dead and alive at the same time, but people use the Schrödinger’s cat metaphor to describe a superposition of quantum states that differ by a large amount.
Dr. Andrea Morello, Professor, University of New South Wales
The antimony atom employed in the study is far more complicated than conventional “qubits,” or quantum building components.
My dream of a spin cat state on a single isolated particle, proposed 35 years ago, has come true by exquisitely controlling a single atomic nucleus that has been isolated from the rest of the universe.
Dr. Barry Sanders, PhD, Professor, Faculty of Science, University of Calgary
The new findings have significant ramifications for researchers using an atom's nuclear spin as the fundamental building block to create a quantum computer.
It was the outcome of extensive global cooperation.
The quantum devices were created and run by several authors from UNSW Sydney and associates from the University of Melbourne. Theory collaborators from the University of Calgary in Canada, Sandia National Laboratories, and NASA Ames in the United States contributed invaluable suggestions on how to build the cat and evaluate its complex quantum state.
Journal Reference:
Yu, X. et. al. (2025) Schrödinger cat states of a nuclear spin qudit in silicon. Nature Physics. doi.org/10.1038/s41567-024-02745-0