Quantum Tunnelling (QT)

Why in news?

• The rate at which the rare but crucial quantum phenomenon known as tunneling occurs has been measured experimentally for the first time, and found to match theoretical calculations.

What is Quantum Tunnelling (or Barrier Penetration)?

• Quantum tunneling is one of the many phenomena where subatomic particles behave in ways classical physics would say is impossible.
• In this case, an object trapped in a way that classically requires a certain energy to escape leaves the trap, despite having less than that amount of energy.
• It’s a consequence, and proof of, the dual wave/particle nature of objects like electrons – a pure particle could not escape, but a wave occasionally can. Phenomena like alpha decay of atomic nuclei depend on quantum tunneling to occur.
• Tunneling plays an essential role in physical phenomena such as nuclear fusion and alpha radioactive decay of atomic nuclei.
• The effect was predicted in the early 20th century. Its acceptance as a general physical phenomenon came mid-century.

Applications of Quantum Tunnelling:

• Scanning Tunnelling Microscope
  • STM is a type of microscope that helps to observe objects at atomic levels.
  • It functions by utilising the connection between quantum tunnelling with distance.
  • STM analyses the surface by using a sharp conducting tip that can differentiate characteristics smaller than 0.1 nm with a 0.01 nm depth resolution. So, individual atoms can be consistently imaged and manipulated.
• Nuclear Fusion:
  • Quantum tunnelling is a crucial part of nuclear fusion.
  • The average temperature of a star’s core is usually not sufficient for atomic nuclei to overcome the Coulomb barrier and kick start thermonuclear fusion.
  • The tunnelling increases the chances of infiltrating this barrier. Though the probability is still low, the huge number of nuclei in the stellar core is enough to drive a steady fusion reaction.
• Electronics
  • Tunnelling is a frequent source of current leakage in very-large-scale integration (VLSI) electronics.
  • The VLSI electronics experience substantial power loss and heating effects that cripple such devices.
  • It is usually considered the lower threshold on how microelectronic device elements can be created.
  • Tunnelling is also a basic technique employed to set the floating gates in flash memory.
  • Cold emission, tunnel junction, quantum-dot cellular automata, tunnel diode, and tunnel field-effect transistors are some of the main electronic processes or devices that use quantum tunnelling.
• Astrochemistry in interstellar clouds:
  • By including quantum tunneling, the astrochemical syntheses of various molecules in interstellar clouds can be explained, such as the synthesis of molecular hydrogen, water (ice) and the prebiotic important formaldehyde
• Quantum Biology
  • Quantum tunnelling is one of the core quantum phenomena in quantum biology.
  • It is essential for both proton tunnelling and electron tunnelling.
  • Electron tunnelling is a critical factor in numerous biochemical redox reactions (cellular respiration, photosynthesis) and enzymatic catalysis. Proton tunnelling also has a key role in spontaneous DNA mutation.

PRACTICE QUESTION

Quantum Tunnelling (QT), sometimes mentioned in news, refers to:

(a) The process when two quantum objects are so strongly correlated that they are described by the same wavefunction.

(b) The process by which a quantum state breaks down, often due to unwanted and uncontrolled interactions

(c) A cryptographic protocol based on the uncertainty principle, where two parties exchange quantum states instead of electronic signals. QKD keeps information absolutely safe, even against an attack from a quantum computer.

(d) A phenomenon in which an object such as an electron or atom passes through a potential energy barrier that, according to classical mechanics, the object does not have sufficient energy to enter or surmount

Answer