Quantum computers only work when they are kept extremely cold. The problem is that today's cooling systems also create noise, which can interfere with the fragile quantum information they are supposed to protect. Researchers at Chalmers University of Technology in Sweden have now introduced a new type of minimal quantum "refrigerator" that turns this challenge into an advantage. Instead of fighting noise, the device partially relies on it to operate. The result is highly precise control over heat and energy flow, which could help make large scale quantum technology possible.
Quantum technology is widely expected to reshape major areas of society. Potential applications include drug discovery, artificial intelligence, logistics optimization, and secure communications. Despite this promise, serious technical barriers still stand in the way of real world use. One of the most difficult challenges is maintaining and controlling the delicate quantum states that make these systems work.
Why Quantum Computers Must Be Near Absolute Zero
Quantum computers built with superconducting circuits must be cooled to temperatures very close to absolute zero (around -- 273 °C). At these temperatures, materials become superconducting, allowing electrons to move without resistance. Only under these extreme conditions can stable quantum states form inside qubits, the basic units of quantum information.
These quantum states are extremely sensitive. Small changes in temperature, electromagnetic interference, or background noise can quickly erase stored information. This sensitivity makes quantum systems difficult to operate and even harder to expand.
As researchers attempt to scale up quantum computers to solve practical problems, heat and noise become harder to control. Larger and more complex systems create more opportunities for unwanted energy to spread and disrupt fragile quantum states.
"Many quantum devices are ultimately limited by how energy is transported and dissipated. 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," says Simon Sundelin, doctoral student of quantum technology at Chalmers University of Technology and the study's lead author.
Using Noise as a Cooling Tool
In a study published in Nature Communications, the Chalmers team describes a fundamentally different kind of quantum refrigerator. Instead of trying to eliminate noise, the system uses it as the driving force behind cooling.
"Physicists have long speculated about a phenomenon called Brownian refrigeration; the idea that random thermal fluctuations could be harnessed to produce a cooling effect. Our work represents the closest realisation of this concept to date," says Simone Gasparinetti, associate professor at Chalmers and senior author of the study.
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