New ‘quantum engine’ does work by flipping the identity of atoms

New ‘quantum engine’ does work by flipping the identity of atoms

Subject : Science and Tech

Section: Awareness in IT

Context:

• Physicists in Germany have come up with a way to convert the energy difference between two quantum states of a group of atoms into work. The device adapts the principles of the familiar classical engine to the subatomic realm, giving physicists a way to study the nascent field of quantum thermodynamics in more detail as well as, possibly, build better quantum computers.

About:

• All subatomic particles can be classified as either fermions or bosons.
• Fermions are the building blocks of matter and bosons are particles that carry the forces acting between them.
• All particles in a system are distinguished by four quantum 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 .

Working:

• Classical engines convert heat into work. For example, the internal combustion engine in a car uses the heat released by the combustion of petrol or diesel to push a piston.
• Overall the engine has four steps: the fuel is compressed, ignition causes the fuel air mix to expand and push the piston out, the mix cools and stops expanding, and the piston is brought back to the first step.
• The quantum engine, or what the researchers are calling a ‘Pauli engine’,has a similar set of four steps. First, the atoms collected in the trap are compressed and kept in a bosonic state. Second, the strength of a magnetic field applied on the atoms is increased by a small amount. Interactions between the atoms and the field cause the former to slip into a fermionic state: they are forced to move out of the lowest energy level and progressively occupy higher levels. Third, the compression applied in the first step is eased. Fourth: the magnetic field strength is reduced to its original value.
• The energy of the atoms increases during the third step and this can be converted to work. The efficiency of the quantum engine is based on how much more energy is released in the third step relative to the energy added to the system in the first step.
• Currently, according to the researchers’ paper, published in Nature on September 27, their quantum engine is 25% efficient. The researchers expect to be able to increase this to 50% or more in future.
• The quantum engine is still a proof of concept. Researchers have demonstrated that their design can be used to force a bunch of atoms to cyclically release energy as they are switched between bosonic and fermionic states. The researchers need to figure out how this energy can be moved from inside the trap to a system on the outside.