A groundbreaking cooling technology could boost quantum computing and cut precious preparation time for important science experiments by weeks.
Scientists often need to generate temperatures that are close absolute zero for quantum computers and astronomy, among others. Such temperatures are known as the ‘Big Chill’ and keep the most sensitive electrical instruments free from interference such as temperature changes. However, the refrigerators used to achieve these temperatures are extremely expensive and inefficient.
However, scientists at the National Institute of Standards and Technology (NIST) – a US government agency – have built a new prototype refrigerator that they claim can achieve the Big Chill much faster and more efficiently.
The researchers published the details of their new machine on April 23 in the journal Nature Communications. They claimed that its use could save 27 million watts of energy per year and reduce global energy consumption by $30 million.
A new kind of refrigerator
Conventional household refrigerators work through a process of evaporation and condensation Living Science. A refrigerant liquid is pushed through a special low-pressure line called an “evaporator coil”.
As it evaporates, it absorbs heat to cool the inside of the refrigerator and then passes through a compressor that turns it back into a liquid, raising its temperature as it is radiated through the back of the refrigerator.
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To achieve the required temperatures, scientists have been using pulse tube refrigerators (PTRs) for more than 40 years. PTRs use helium gas in a similar process, but with much better absorption of heat and no moving parts.
Although it is effective, it consumes enormous amounts of energy, is expensive to use and takes a long time. However, the NIST researchers also found that PTRs are needlessly inefficient and could be significantly improved to shorten cooling times and reduce overall costs.
In the study, the scientists said that PTRs “suffer from major inefficiencies”, such as being optimized “for performance only at their base temperature” – usually around 4 Kelvin. It means that PTRs operate at a very inefficient level during cooling, she added.
The team found that by adjusting the design of the PTR between the compressor and the refrigerator, helium was used more efficiently. During cooling, some of it is normally pushed into a relief valve instead of being pushed around the circuit as intended.
Quantum computers at a fraction of the cost
Their proposed redesign includes a valve that contracts as temperatures drop to prevent helium from being wasted in this way. As a result, the NIST team’s modified PTR reached the Big Chill 1.7 to 3.5 times faster, the scientists said in their paper.
“In smaller quantum circuit prototyping experiments, where cooling times are currently comparable to characterization times, dynamic acoustic optimization can significantly increase measurement throughput,” the researchers wrote.
The researchers said in their study that the new method could save at least a week on experiments at the Cryogenic Underground Observatory for Rare Events (CUORE) – a facility in Italy used to search for rare events such as a currently theoretical form of radioactive decay. . To obtain accurate results from these facilities, minimal background noise must be achieved.
Quantum computers require a similar level of isolation. They use quantum bits, or qubits. Conventional computers store information in bits and encode data with a value of 1 or 0 and perform calculations sequentially, but qubits occupy a superposition of 1 and 0, thanks to the laws of quantum mechanicsand can be used to process calculations in parallel. However, qubits are incredibly sensitive and need to be separated from as much background noise as possible, including the small fluctuations in thermal energy.
The researchers said that theoretically even more efficient cooling methods could be achieved in the near future, which could lead to faster innovation in the quantum computing space.
The team also said that their technology could alternatively be used to achieve extremely cold temperatures in the same time but at a much lower cost, which could benefit the cryogenics industry and reduce costs for non-time-intensive experiments and industrial applications to lower. The scientists are currently working with an industrial partner to commercially release their improved PTR.
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