Quantum Leap in Cooling: Swedish Researchers Harness Noise to Stabilize Quantum Computers
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A groundbreaking new approach to quantum computing, developed by researchers at Chalmers University of Technology in Sweden, leverages noise – traditionally an enemy of quantum stability – to achieve unprecedented control over heat and energy flow. This innovation could pave the way for the development of large-scale, reliable quantum technology with transformative potential across numerous industries.
Quantum computers promise to revolutionize fields like drug discovery, artificial intelligence, logistics, and secure communications. However, a significant hurdle remains: maintaining the delicate quantum states necessary for computation. These states are incredibly sensitive to environmental disturbances, making stable operation and scalability a major challenge.
The Challenge of Absolute Zero
Current quantum computers built with superconducting circuits require extremely low temperatures – around -273°C (near absolute zero). At these frigid temperatures, materials exhibit superconductivity, allowing electrons to flow without resistance. This is crucial for forming stable quantum states within qubits, the fundamental units of quantum information.
However, even at these extreme temperatures, maintaining stability is difficult. “Many quantum devices are ultimately limited by how energy is transported and dissipated,” explains a doctoral student and the study’s lead author. “Understanding these pathways and being able to measure them allows us to design quantum devices in which heat flows are predictable, controllable and even useful.” As systems grow more complex, controlling heat and noise becomes exponentially harder.
Turning Noise into an Asset
The Chalmers team has taken a radically different approach, introducing a novel quantum “refrigerator” that doesn’t fight noise, but instead utilizes it. Published in Nature Communications, the research details a system based on the principle of Brownian refrigeration – the idea that random thermal fluctuations can be harnessed for cooling.
“Our work represents the closest realisation of this concept to date,” says an associate professor and senior author of the study. At the heart of the device is an “artificial molecule” constructed from superconducting electrical circuits, mimicking the behavior of natural molecules. This artificial molecule is connected to multiple microwave channels. By injecting carefully controlled microwave noise – random signal fluctuations – the researchers can precisely guide heat and energy flow.
The system functions by creating “hot” and “cold” reservoirs connected only when noise is introduced through a third port. “We were able to measure extremely small heat currents, down to powers in the order of attowatts, or 10-18 watt,” explains the lead author. “If such a small heat flow were used to warm a drop of water, it would take the age of the universe to see its temperature rise one degree Celsius.”
Implications for Scalable Quantum Technology
This level of control is particularly vital for larger quantum systems, where heat is generated during qubit operation and measurement. The ability to manage heat directly within quantum circuits, rather than relying on conventional cooling systems, could significantly improve stability and performance.
The quantum refrigerator can operate in multiple modes, functioning as a refrigerator, a heat engine, or even amplifying thermal transport, depending on the conditions. “We see this as an important step towards controlling heat directly inside quantum circuits, at a scale that conventional cooling systems can’t reach,” says a researcher and co-author of the study. “Being able to remove or redirect heat at this tiny scale opens the door to more reliable and robust quantum technologies.”
This research represents a significant step forward in overcoming the thermal challenges that have long plagued the development of practical quantum computers, bringing the promise of this revolutionary technology closer to reality.
The study, Quantum refrigeration powered by noise in a superconducting circuit, was authored by Simon Sundelin, Mohammed Ali Aamir, Vyom Manish Kulkarni, Claudia Castillo-Moreno, and Simone Gasparinetti from the Department of Microtechnology and Nanoscience at Chalmers University of Technology. The quantum refrigerator was fabricated at the Nanofabrication Laboratory, Myfab, at Chalmers University of Technology. Funding was provided by the Swedish Research Council, the Knut and Alice Wallenberg Foundation, the European Research Council, and the European Union.
