Pauli’s Exclusion Principle
All subatomic particles can be classified as either fermions or bosons.
Fermions are the building blocks of matter; bosons are particles that carry the forces acting between them.
Now, when a bunch of particles are cooled to very nearly absolute zero, so that their quantum nature comes to the fore, they would all like to have the lowest energy possible – but they can’t. This is known as Pauli’s exclusion principle.
All particles in a system are distinguished by four quantum numbers, sort of like their Aadhaar numbers.
The values of the four numbers together tell us something about how much energy a particle has.
The exclusion principle states that, in a given system, no two particles can have the same four quantum numbers – that is, they can’t occupy the same energy level.
Fermions are particles that are bound by this rule. So they recursively occupy the lowest one available, until all possible energy levels are filled.
Bosons are not bound by the exclusion principle principle: they can all occupy the same lowest energy level at a given low temperature. This is why, for example, superconductivity is possible.
Conversion of Particles:
To create a quantum engine, physicists needed a way to convert some particles from being bosons to fermions.
They found that by cooling fermions and prodding them to interact using a magnetic field, they could behave like bosons.
The quantum engine, referred to as a 'Pauli engine,' involves four steps.
First, the particles are compressed and kept in a bosonic state.
Then, a magnetic field is increased, causing interactions between particles and the field, forcing them into a fermionic state.
During the third step, compression is eased, and in the fourth step, the magnetic field strength is reduced to its original value.
Energy Conversion:
The energy of the particles increases during the third step, and this energy can be converted into work.
The efficiency of the quantum engine is determined by how much more energy is released during the third step compared to the energy added in the first step.
Efficiency and Future Prospects:
The current efficiency of the quantum engine is 25%, with expectations to increase it to 50% or more in the future.
Applications in Quantum Computing:
In cooling the particles in a quantum computer, similar to how an air conditioner uses an engine to cool a room.
Challenges and Future Research:
While the quantum engine is a proof of concept, the researchers still need to figure out how to move the energy from inside the trap to an external system.
They are exploring options for achieving this, which may involve coupling microscopic mechanical objects to the gas.
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