Quantum states are not fixed or deterministic due to several fundamental principles and phenomena in quantum mechanics. Here are a few key reasons:
Superposition: One of the fundamental principles of quantum mechanics is superposition. It states that quantum systems can exist in a combination or superposition of multiple states simultaneously. For example, a quantum particle, such as an electron or a photon, can exist in a superposition of being in multiple locations or having multiple properties at the same time. This superposition of states allows quantum systems to exhibit a range of possibilities rather than being fixed in a single state.
Measurement and Wavefunction Collapse: When a measurement is made on a quantum system, it interacts with the system and causes the collapse of the superpositioned state into a definite outcome. This phenomenon is known as wavefunction collapse. The collapse is probabilistic in nature, meaning that the measurement outcome is determined by the probabilities associated with the superpositioned states. The specific outcome of a measurement cannot be predicted with certainty, and it is only upon measurement that a definite value is observed, while the other possibilities "collapse" and become unobservable.
Uncertainty Principle: The Heisenberg uncertainty principle is another fundamental aspect of quantum mechanics. It states that there is a fundamental limit to the precision with which certain pairs of physical properties, such as position and momentum, or energy and time, can be simultaneously known. This inherent uncertainty arises due to the wave-like nature of quantum systems and the complementary relationship between certain observables. Consequently, the precise values of these properties are not fixed but exist within a range of possible values.
Quantum Entanglement: Quantum entanglement is a phenomenon where two or more particles become correlated in such a way that their quantum states are intrinsically linked. When particles are entangled, the measurement or manipulation of one particle can instantaneously affect the state of the other particle, regardless of the distance between them. This non-local correlation introduces an element of unpredictability and non-determinism into the behavior of entangled systems.
These principles and phenomena in quantum mechanics contribute to the non-fixed nature of quantum states, allowing for superposition, probabilistic outcomes, uncertainty, and entanglement. They form the basis for the unique properties and potential applications of quantum computing, quantum communication, and other areas of quantum physics.