A QUANTUM trick could pave the way for the world’s smallest fridge – one built on the atomic scale. The small but mighty cooler could brush the ultimate chill of absolute zero to keep quantum computers running smoothly, according to a team of theoretical physicists.
Blueprints for the device, designed by , and at the University of Bristol, UK, suggest that the fridge would consist of two quantum bits, or qubits, which interact with a third qubit in such a way that it would cool.
Each qubit has two possible energy states: high, or “1”, and low, or “0”. The three qubits together share a group state, such as 110. The team’s theoretical system is chosen so that the 101 and 010 group states are exactly equal in energy, meaning the system can swap between the two easily. Next, the team imagined that the first qubit is attached to a heat bath, providing it with a constant source of energy that should increase the probability that the qubits will take on the 101 state. However, the qubits interact on a quantum level with the unexpected consequence that the probabilities flip, making the 010 state more likely. As the probability of the third qubit being in state 0 increases, its temperature falls. Increasing the probability is easy: turn up the heat on the first qubit. The work will appear in Physical Review Letters.
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The team says that the fridge could be used to chill the qubits in a quantum computer, cutting out the thermal noise that can upset their delicate quantum properties.
“The fridge could chill the qubits in a quantum computer, cutting out thermal noise”
However, to reach super-cool temperatures within a quantum computer the fridge would need a super-hot heat bath. ‘s team at the University of Waterloo in Ontario, Canada, has made a quantum refrigeration system that runs on similar principles to the Bristol team’s blueprint, but the cooling is driven by an external magnet acting on the qubits rather than heat. They have used their fridge to cool a carbon atom to -95°C, but they intend to approach absolute zero in future experiments.
