Finnish researchers have achieved a major breakthrough in ultra-sensitive measurement technology by detecting amounts of energy smaller than 1 zeptjoule, or less than one billionth of a joule. This breakthrough could improve quantum computing technology, support the search for dark matter, and ultimately make it possible to count the number of individual photons.
Quantum mechanics operates on incredibly small scales, and scientists are constantly developing more precise tools to measure and control phenomena such as photons (particles that carry light). Improved precision could open the door to more powerful quantum devices and new ways to study some of the universe’s biggest mysteries.
A zeptojoule is an almost unimaginably small amount of energy. This is approximately the amount of work required to move a red blood cell one nanometer upward under Earth’s gravity.
The research team is led by Aalto University Academy Professor Mikko Mottonen, in collaboration with quantum computing company IQM and the Finnish Technology Research Center (VTT). Their findings were published in the magazine nature electronics.
Ultra-sensitive quantum energy detector
To reach this level of sensitivity, the researchers used a calorimeter, a device designed to measure extremely small changes in thermal energy. Measuring this small signal is much more difficult than simply sending a beam into a detector and reading the results.
The scientists exposed a sensor made of two different metals to microwave pulses. Some were composed of superconductors, materials that allow electricity to flow freely without resistance. Other parts use normal conductors that resist the flow of electricity.
“The combination of metals makes superconductivity a very fragile phenomenon, weakening as soon as the temperature of the cryogenic conductor increases even slightly, making it a very sensitive setup,” says Mottonen, who is also the founder of the quantum computing unicorn IQM.
After carefully filtering the signal, the researchers were able to detect an electromagnetic pulse as small as 0.83 zeptjoules. The researchers say this is the first time a calorimetric device has reached such sensitivity.
Quantum computing and its impact on dark matter
This advance may eventually allow scientists to count individual photons, a long-standing goal of quantum technology and astrophysics.
“We want to be able to measure inputs with arbitrary arrival times with this setup, which is important in cases such as detecting dark matter axions in the Universe when we don’t know when they will reach the system.”
The researchers also believe the technique could be useful in quantum computers, since calorimeters operate at the same ultracold milliKelvin temperatures required by qubits, the basic units of quantum information.
“The calorimeter operates at the same milliKelvin temperatures that the qubits require. This introduces fewer disturbances to the system, as there is no need to heat the device or amplify the qubit measurement signal to get the result. In the future, for example, our device could become a component for reading qubits in quantum computers.”
Research facilities and funding
The research was carried out using the facilities of Otanano, Finland’s national research infrastructure for nano, micro and quantum technologies.
Funding for this project came primarily from the Future Makers initiative, supported by the Jane and Artos Erkko Foundation and the Finnish Technology Industry Centenary Foundation.
