Breakthrough quantum heat engine brings larger quantum computers a step closer

A micro-scale quantum heat engine that converts thermal energy to usable work under near-zero temperatures has paved the way for the realization of a more efficient quantum computer.

The scientists at Aalto University have developed the first machine capable of carrying out an entire quantum mechanical cycle within a superconducting circuit. The entire machine measures less than the size of a grain of sand. The quantum bit, which is a quantum mechanical carrier of information, is used as the substance in the engine.

Academy Professor Mikko Möttönen led the project, which was published in Nature Communications. The machine uses the same basic idea as engines in cars and power stations. Such machines create work through the exchange of energy from warm to cold environments.

The machine developed by Aalto does so on a microscopic chip where quantum physics governs the behavior of minute energies.

Researchers use one refrigerator to heat and cool the qubit

The engine contains a flux-tunable transmon qubit linked to a resonator and a quantum circuit refrigerator. Transmons are already common in superconducting quantum computers.

Engineers use microwave signals to control them while they hold and process quantum information. Here, the transmon replaced the gas that would normally serve as the working material inside a standard engine.

The refrigerator carried out two opposite tasks. Normal heat engines often depend on separate hot and cold sources. The Aalto team changed one device’s settings so it could warm the qubit during one part of the process and cool it during another. Researchers also changed the qubit’s energy level at carefully chosen times.

That sequence completed all four parts of a quantum Otto cycle. Gasoline engines use the ordinary Otto cycle through the compression and expansion of fuel and air inside cylinders.

The new machine had no compressed gas. A single qubit exchanged extremely small amounts of energy inside a circuit kept at cryogenic temperatures.

Study first author Tuomas Uusnäkki explained the setup. “In our experiment, we built a nanofabricated heat engine using superconducting circuits and operated it in a cryostat near absolute zero. At its heart is a transmon qubit, one of the basic building blocks of modern quantum technologies,” Tuomas said.

Bitcoin developers track how quantum algorithms could affect network security

Quantum computing also matters to Bitcoin, though the security question is separate from the heat engine. Satoshi Nakamoto never treated classical brute force as a practical danger, and that remains true. The quantum issue has two parts. One concerns hashing, while the other concerns digital signatures.

Grover’s algorithm can speed up searches through possible answers. If used against SHA-256, it would lower the system’s effective protection from 256 bits to roughly 128 bits.

That level remains far beyond today’s available machines. Researchers say an attacker would need quantum hardware far larger than anything that currently exists.

Shor’s algorithm presents the bigger concern because it attacks signatures instead of hashes. A powerful enough quantum computer could calculate a private key from a public key already exposed on the elliptic curve used by Bitcoin (BTC).

About 7 million Bitcoin, close to 35% of the total supply, sit in addresses with visible public keys. Those holdings could become vulnerable if the required hardware is ever built.

Quantum AI at Google, a unit of Alphabet Inc. (NASDAQ: GOOGL), revealed a study in 2026 that lowered the projected number of physical qubits required to crack Bitcoin’s curve to around 500,000. Modern-day quantum computers usually have no more than 1,000 to 1,500 qubits.

Researchers see a realistic threat between 2029 and 2035, based on advancements in error correction.

Satoshi discussed hash security several times in 2010, including the possibility of a partial SHA-256 collision. His proposed response stayed the same. Developers need to secure the honest blockchain first, and then replace the compromised function.

The subsequent updates of Bitcoin did not affect the hash function used on the network. Segregated Witness was introduced in 2017, while Taproot was introduced in 2021.

Quantum resistance started becoming a big deal issue among developers around 2020 thanks to a rise in awareness about Grover’s and Shor’s algorithms.

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