Quantum computers, often hailed as the next frontier in computing, promise transformative capabilities far beyond the reach of classical machines.
From revolutionising drug discovery and optimisation problems to securing communication systems and accelerating clean energy research, the potential of quantum computing is staggering.
However, a persistent technical challenge has kept these machines from reaching their full potential: decoherence – the process where fragile quantum information degrades due to environmental interference.
Now, a groundbreaking development by scientists at the National Physical Laboratory (NPL), in partnership with Chalmers University of Technology and Royal Holloway University of London, may offer a vital key to solving this issue.
For the first time, researchers have successfully imaged individual defects in superconducting quantum circuits, a crucial step toward building more stable and reliable quantum systems.
Tiny flaws in superconducting quantum circuits
Superconducting circuits are one of the leading architectures for quantum processors, favoured by tech giants and academic researchers alike.
These quantum circuits rely on maintaining extremely low temperatures – near absolute zero – to function without electrical resistance. But hidden within these circuits are minute imperfections known as two-level system (TLS) defects.
Although scientists have suspected these defects of causing decoherence for over 50 years, it had never been possible to visually detect and study them inside an operational quantum device – until now.
A new instrument that sees the unseeable
To overcome this long-standing obstacle, NPL scientists have developed an innovative instrument capable of locating and analysing individual TLS defects within functioning quantum circuits.
The tool combines advanced scanning microscopy with cryogenic engineering, operating inside a completely light-tight chamber at temperatures just above absolute zero.
This ensures minimal external interference, allowing for the real-time observation of the defects’ effects on quantum coherence.
The imaging system produces visual patterns resembling ripples caused by raindrops, where each ring indicates the presence and influence of a defect.
By capturing this data, researchers can now quantify how each TLS defect interacts with the circuit and contributes to quantum noise and instability.
Paving the path to fault-tolerant quantum computing
This pioneering research marks a significant leap forward in quantum technology. For the first time, scientists can go beyond theoretical understanding and physically map the noise landscape of superconducting quantum circuits.
The implications are enormous. With this imaging capability, future work can focus on the chemical identification and elimination of these defects, potentially leading to quantum chips that are far more robust and scalable.
By addressing the root cause of decoherence, engineers can inch closer to creating fault-tolerant quantum computers, a milestone necessary for real-world applications in everything from machine learning to materials science.
Dr Riju Banerjee, a senior scientist at NPL and one of the lead authors of the paper, added: “For years, people have believed that TLS defects perturb quantum circuits.
“It is remarkable to finally be able to visualise the fluctuations and decoherence each TLS defect causes as it interacts with the circuit.
“We now have a new tool with which we can learn so much more about these nasty defects that plague quantum circuits. It can now help us find ways to get rid of these defects in the future.”
A new era for quantum circuits
This discovery isn’t just a technical triumph – it’s a paradigm shift.
As quantum computing edges closer to practical reality, innovations like this imaging breakthrough are critical to overcoming the engineering bottlenecks that have slowed progress for decades.
With the ability to see and eventually control TLS defects, scientists are now equipped to fine-tune quantum circuits at an unprecedented level.
This marks a decisive step toward a future where quantum computers no longer live solely in the lab, but in industries, research centres, and even healthcare systems worldwide.
In short, the quantum revolution just became a lot clearer, one defect at a time.