New device can measure energy levels with unprecedented accuracy and sensitivity, delivering major breakthroughs for quantum technology, Nanodevice accurately measure Trillion times lower than normal.
Finnish scientists have developed a nanodevice that can measure the full power of microwave radiation (Nanodevice accurately measure Trillion times lower than normal) up to the femtowatt level at very low temperatures – a number of trillions of times smaller than what is usually used in the measurement of power. The device is able to speed up the speed of measurement in quantum technology.
Measuring very low power
Quantum science takes place at very low temperatures using a device called a dilution refrigerator. These experiments must be done at low energies – down to the energy level of one photon or even less. Researchers need to measure these energy levels as low as possible, which also accounts for heat – a persistent problem for quantum devices.
To measure temperature in quantum research, scientists use a special type of thermometer called a bolometer. The team led by Mikko Möttönen, assistant professor of quantum technology at Aalto and VTT, recently developed a precision bolometer at Aalto, but the device showed more uncertainty than they expected. Although this allowed them to see the relative power level, they could not determine the absolute power level.
In the new study, Möttönen’s team worked with researchers from the quantum technology companies Bluefors and IQM, and the Finnish Research Institute of Technology VTT to improve the bolometer. This work was published today as an editorial in the review of scientific instruments.
“We added a heating element to the bolometer, so that we could apply a known heating current and measure the voltage. Since we know the precise amount of power we put into the radiator, we can calibrate the power of the input radiation to the power of the radiator. The result is a bolometer that works at low temperatures, which allows us to measure the full energy at cryogenic temperatures,” says Möttönen.
According to Russell Lake, director of quantum applications at Bluefors, the new bolometer is a significant step forward in measuring microwave energy.
“Commercial power is usually measured in milliwatt units. This bolometer performs well and reliably at femtowatt or less. That’s trillions of times less power than used in power systems.
Covers both depth and broad scales
Möttönen explains that the new bolometer can improve the performance of quantum computers. “For accurate results, the measurement lines used to control the qubits must be low temperature, free of thermal photons and high radiation. Now, with this bolometer, we can measure radiation heat without interference from the qubit circuit,” he said.
A bolometer also covers a wide range of frequencies.
“The sensor is broadband, which means it can measure how much energy is applied in different forms. This is given by quantum technology, since the sensor usually only has a very narrow band,” he said. Jean-Philippe Girard, scientist at Bluefors who also worked with Aalto on the device explains.
The team says that the bolometer provides a major advance in the field of quantum technology.
“Microwaves are used in wireless communications, radar technology and many other areas. They have their own way of making accurate measurements, but they have no way of doing the same thing when they measure the weak signal for quantum technology. “The bolometer is an advanced diagnostic tool that has been missing from quantum technology applications until now,” said Lake.
Source: Aalto University
