While it is true that decoherence can suppress interference effects and that complete isolation of a quantum system is difficult to achieve in practice, it does not imply that subatomic particles in the real world always behave classically. Quantum behavior can still manifest itself in various ways, even in the presence of decoherence and interactions with the environment. Here are a few points to consider:
Partial Decoherence: Decoherence refers to the process by which a quantum system interacts with its environment, leading to the loss of coherence between different quantum states. While decoherence can degrade or eliminate interference effects between distinct states, it does not completely erase all quantum behavior. In many cases, decoherence affects only specific aspects of a quantum system's behavior, while other quantum features may remain intact.
Macroscopic Quantum Phenomena: Although decoherence tends to suppress interference at large scales, there are instances where quantum effects can still be observed macroscopically. Examples include superconductivity, superfluidity, and quantum coherence in certain materials. These phenomena involve a large number of particles and demonstrate collective quantum behavior that persists even in the presence of decoherence.
Quantum Technologies: Quantum technologies, such as quantum computing, quantum communication, and quantum sensing, rely on harnessing and manipulating quantum effects in real-world systems. While these technologies face challenges due to decoherence, significant progress has been made in developing error correction techniques and robust quantum systems that can maintain coherence and perform quantum operations.
Quantum Measurements: Even in the presence of decoherence, the process of measurement in quantum mechanics remains distinct. Quantum measurements can exhibit non-classical behavior, such as entanglement, superposition, and quantum correlations. While the measurement process itself may introduce classical features, the underlying quantum nature of the system is still fundamental.
Fundamental Quantum Principles: Quantum mechanics, as a theory, provides a consistent mathematical framework that accurately describes a wide range of phenomena in the microscopic world. The principles of superposition and entanglement, which are central to quantum mechanics, continue to be experimentally confirmed, indicating that quantum behavior persists despite the challenges posed by decoherence.
In summary, while decoherence and the lack of complete isolation can impact the observation of interference effects and make quantum behavior more challenging to observe, it does not mean that subatomic particles always behave classically in the real world. Quantum effects can still emerge, and various phenomena and technologies continue to demonstrate the distinctly quantum nature of particles and systems, albeit in the presence of environmental interactions.