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The new type of thermometer developed by researchers at Chalmers University of Technology in Gothenburg, Sweden, can measure temperatures with high accuracy during quantum calculations. This breakthrough is a valuable benchmark in quantum computing and opens the door to experiments in the exciting field of quantum thermodynamics.
Coaxial cables and waveguides are critical components of quantum computers. These structures guide waveforms and are the crucial connection between the quantum processor and the classical electronics that control it. The waveguides carry microwave pulses along their path to the quantum processor. They are then cooled to shallow temperatures. The waveguide filters and attenuates the vibrations, allowing the susceptible quantum computer’s stable quantum states to function.
Researchers must ensure that the waveguides transmit no noise from thermal motion electrons. This will allow them to control the machine to the maximum extent possible. To ensure ultimate control, they must measure the temperature at the microwave waveguide’s cold end, where the controlling pulses are delivered. The risk of errors in the qubits is minimized by working at the lowest temperature. Researchers have been able to measure the temperature directly just now. This was due to a delay of significant amount. The Chalmers researchers have created a novel thermometer to measure shallow temperatures directly at the receiving end. This is very accurate and provides a high level of time resolution.
The thermometer’s superconducting circuit is directly connected to the waveguide being measured. It’s simple and, at the millikelvin level, probably the most sensitive and fastest thermometer in the world,” Simone Gasparinetti, Assistant Professor at Chalmers University of Technology’s Quantum Technology Laboratory.
Important for measuring the performance of quantum computers
Wallenberg Centre for Quantum Technology (WACQT) aims to create a quantum computer based on superconducting systems. It will have at least 100 qubits and perform correct calculations by 2030. The processor must operate at a temperature of 10 to 20 degrees Celsius. Researchers now have an essential tool to measure how well their systems work and identify weaknesses. This is a crucial step in advancing technology and achieving their goals.
“A temperature corresponding to a certain number of thermal photons is called a temperature. This number decreases exponentially as temperature increases. Per Delsing, Professor at Chalmers University of Technology’s Department of Microtechnology and Nanoscience and leader of WACQT, says that if we can lower the temperature at which the waveguide meets the qubit down to 10 millikelvins, then the risk of errors in our qubits will be greatly reduced.”
Suppliers who want to guarantee the quality and reliability of their components, such as cables used to transmit signals down to quantum states, need accurate temperature measurements.
Quantum thermodynamics offers new opportunities.
Quantum mechanical phenomena like superposition, entanglement, and decoherence are revolutionizing future computing and thermodynamics. The thermodynamic laws may change at the nanoscale. This could be used to create more powerful engines and faster-charging batteries.
“For the past 15-20 years, people have been studying how quantum phenomena might alter thermodynamic laws. But the search for a true quantum advantage in thermodynamics remains open,” Simone Gasparinetti says. He recently established his research group and intended to contribute to a new range of experiments.
The new thermometer can measure, for instance, the scattering of thermal microwaves from a circuit that acts as a refrigerator or quantum heat engine.
“Standard thermometers are fundamental in the development of classical thermodynamics. Our thermometer may be considered pivotal in developing quantum thermodynamics in the future,” Marco Scigliuzzo (doctoral student, Chalmers University of Technology, Department of Microtechnology and Nanoscience) says.
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