In quantum mechanics, macroscopic objects are not typically described by quantum tunneling because they exhibit emergent properties that are effectively described by classical physics. This phenomenon is known as the classical-quantum boundary or the quantum-classical transition. There are several reasons why macroscopic objects are considered to be effectively incapable of quantum tunneling:
Decoherence: Macroscopic objects interact with their environment, leading to a process called decoherence. Decoherence causes quantum superpositions, which are fundamental to quantum tunneling, to collapse quickly. The interactions with the environment, such as particle collisions or electromagnetic interactions, introduce random phase changes that effectively destroy the delicate quantum interference necessary for tunneling to occur.
Many-body Interactions: Macroscopic objects are composed of a large number of particles interacting with each other. The complexity of these interactions and the sheer number of particles involved make it extremely challenging to describe the system using purely quantum mechanical principles. Instead, classical statistical mechanics and thermodynamics provide effective descriptions of macroscopic behavior.
Energy Considerations: Quantum tunneling is governed by the uncertainty principle and the wave nature of particles. The probability of tunneling decreases rapidly with increasing mass and size of objects due to the associated increase in energy barriers. For macroscopic objects, the energy barriers involved in quantum tunneling become extremely high, making the tunneling probability vanishingly small.
While quantum tunneling is not typically observed in macroscopic objects, it is worth noting that there are situations where macroscopic quantum phenomena can be observed under specific conditions. For example, in superconductors, superfluids, or Bose-Einstein condensates, macroscopic quantum effects can occur due to the collective behavior of a large number of particles. These systems exhibit quantum coherence on a macroscopic scale and can display phenomena such as quantum tunneling or macroscopic quantum superpositions.
In summary, macroscopic objects are considered to be effectively incapable of quantum tunneling due to the presence of decoherence, many-body interactions, and high energy barriers. While emergent properties in macroscopic systems may arise from the underlying quantum behavior of their constituent particles, the classical description becomes appropriate at the macroscopic scale.