Scientists at UNSW Sydney have achieved a major milestone in quantum technology by creating a real-life version of the famous “Schrödinger’s cat” thought experiment—inside a silicon chip.
This breakthrough could lead to a more robust way to perform quantum computations, tackling one of the biggest challenges in building a working quantum computer: error correction.
What is Schrödinger’s cat?
The idea of Schrödinger’s cat is a classic example used to explain quantum mechanics.
It imagines a cat in a box that is simultaneously dead and alive, depending on whether a radioactive atom decays.
This strange concept is called “superposition,” where particles exist in multiple states at the same time until observed.
In this study, published in Nature Physics, the researchers used an atom of antimony as the “cat.” Antimony is a heavy atom with eight possible spin directions, much more complex than the two states used in standard quantum bits, or qubits.
The atomic cat
In quantum computing, information is stored in qubits, which are typically described as “0” (spin down) or “1” (spin up). However, these qubits are very fragile—one small error can flip their state, potentially scrambling the stored information.
By using antimony’s eight spin states, the researchers created a more resilient system. Lead author Xi Yu explained: “Our ‘cat’ has seven lives. It would take seven consecutive errors to completely scramble the information.”
This makes the antimony atom much more robust compared to traditional qubits, providing greater error tolerance and paving the way for reliable quantum computers.
A silicon-based quantum cat
The team embedded their “Schrödinger’s cat” in a silicon quantum chip, similar to those found in everyday computers and phones but modified to access the quantum state of a single atom. The chip was fabricated at UNSW, and the antimony atom was precisely inserted by researchers at the University of Melbourne.
“By hosting the atomic ‘cat’ in silicon, we can control its quantum state with high precision,” said Dr. Danielle Holmes, who fabricated the chip. “Using silicon also means this technology can eventually be scaled up with the same methods used to build today’s computer chips.”
The ability to create a resilient quantum system in a silicon chip is a game-changer for quantum computing. Traditional qubits are prone to errors that can quickly disrupt calculations, but the antimony-based system allows more room for error. Even if errors occur, they can be detected and corrected before causing significant problems.
“This is like seeing a cat come home with a scratch. It’s not dead, but you know something happened and can take action before it gets worse,” explained Professor Andrea Morello, who led the study.
The research involved teams from UNSW Sydney, the University of Melbourne, and international collaborators from the U.S. and Canada. Together, they developed and tested this revolutionary system.
“This project shows the power of collaboration,” said Prof. Morello. “By combining expertise from around the world, we’ve taken a big step toward building reliable quantum computers.”
The next goal for the team is to demonstrate full quantum error correction, a critical step in making quantum computers practical for real-world use.
