Quantum locking, or flux pinning, is the phenomenon where a superconductor is “pinned” in space when placed above a magnet. Flux pinning could be helpful in many operations in space, such as docking and on-orbit assembly, require two or more bodies to be nearby. These tasks require high-level precision, as well as intense control abilities. This is where quantum locking kicks in.

A superconductor flux pinned on top of a magnet

What is Quantum Locking?

As previously mentioned, quantum locking is the process in which a superconductor is placed above a magnet. The superconductor then proceeds to “pin” itself in space. Flux pinning only occurs on type-II superconductors, due to their magnetic penetration abilities. 

How does Quantum Locking work?

Quantum locking describes the interaction between a superconductor and a magnetic field. The magnetic field provokes current vortices in the superconductor which resist the change in magnetic flux, happening on top of the superconductor’s surface. This causes a stiffness effect that influences the motion of the superconductor across the magnetic field’s surface. 

The Applications of Quantum Locking

In the future, we could implement quantum locking in numerous sectors, such as lifts, frictionless joints, and transportation. One example of transportation could be a modified version of the MagLev system, called Maglev Cobra. This system is currently being developed by the Federal University of Rio de Janeiro and aims for a smaller form factor than existing urban rail systems.

Conclusion

Quantum locking has a place in future technologies we should keep investigating. Frictionless transportation and precise aircraft construction are some technological advancements we wouldn’t want to miss out on.

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What is Superconductivity?

Superconductivity is a set of physical properties that can be noticed in certain materials. Some of these properties can be the vanishing of electrical resistance (a measure of its opposition to the flow of electric current) which causes the expulsion of magnetic fields. 

Normal, metallic conductors decrease their resistance as their temperature is lowered to near absolute zero.

However, superconductors have a specific and critical temperature below which their resistance drops to zero. This means that if there were to be an electric current flowing through a loop made out of superconducting wire, it would keep circulating without dissipating any energy. 

When a superconductor transitions to its superconducting state, as it is cooled below its critical temperature, the Meissner effect takes place. This consists of the expulsion of a magnetic field from the superconductor.

Types of Superconductivity

The superconducting state can be terminated by an increase in temperature or in the applied magnetic field, which then penetrates the material and suppresses the Meissner effect. Superconductors can be classified into two kinds, based on their response to a magnetic field.

• Type 1 – also known as soft superconductors these types of superconductors lose their superconductivity very easily. When a given threshold is surpassed, the magnetic field suppresses the magnetic field, breaking the superconductive state.

• Type 2 – also known as hard superconductors, these superconductors lose their superconductivity gradually when exposed to the external magnetic field. Type 2 superconductors preserve their superconducting properties in the presence of intense magnetic fields, due to their ability to tolerate local penetration of the magnetic field. This behavior is explained by the existence of a mixed state where superconducting and non-superconducting areas coexist within the material.

Superconductors can also be classified by temperature.

• High-temperature – a superconductor is considered high temperature if it achieves its superconducting state when it reaches a temperature of more than -243°C (-405.67°F, 30 Kelvin).

• Low-temperature – a superconductor is considered low temperature if it achieves its superconducting state when it reaches a temperature of less than -243°C (-405.67°F, 30 Kelvin).

BCS Theory

Traditional physics can’t seem to explain the superconducting behavior, and neither does the elementary quantum theory. In 1957 three American researchers (John Bardeen, Leon Cooper, and John Schrieffer) managed to establish the microscopic theory of superconductivity, which allowed a better comprehension of the subject. 

Cooper had found out that electrons in a superconductor are grouped in pairs, called Cooper pairs.  The motions of all of the Cooper pairs within a single superconductor are correlated and they constitute a system that functions as a single entity. 

Application of an electrical voltage to the superconductor causes all Cooper pairs to move, constituting a current. When the voltage is removed, the current continues to flow indefinitely because the pairs encounter no opposition.

 For the current to stop, all of the Cooper pairs would have to be halted at the same time, a very unlikely occurrence. As a superconductor is warmed, its Cooper pairs separate into individual electrons, and the material becomes normal, or nonsuperconducting.

Conclusion

In future articles, we will show some cool applications of superconductivity, such as quantum locking. 

Sources: wikipedia.com, home.cern, britannica.com, sciencedirect.com

PATRONS: Ayrton M.

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