Quantum entanglement
Quantum entanglement
The quantum world is weird! But it is real. Despite of not having a solid underlying dynamical theory, the generic framework of quantum mechanics (QM) has been proved to be correct.
One of the most important aspects of QM is quantum entanglement. Quantum entanglement refers to the phenomenon that the properties of two systems are inherently correlated, regardless of the possible vast spatial distance between them. To this extent, it is insightful to visualize a simple example:
Imagine two identical balls bounced off from each other in free space. If we know their initial momenta, we can say with certainty what their final momenta should be even if they are at the two ends of the Universe, as long as there is absolutely no external intervention. This is "classical entanglement": the final correlation was already determined at the time they bounce off from each other.
Imagine two electrons entangled with each other after some initial interaction. To be specific, let's say that their spins are entangled, so that if the first electron is spin up, the other one is spin down, and vice versa. Then, they are also brought to the two ends of the Universe. Unlike the classical case, we are now unable to say anything about the outcome of each system, because each electron could have either spin up or spin down. This is "quantum entanglement": the correlation between two systems is "known to the Universe", but will not be revealed until one or both of the systems are measured. The origin of quantum entanglement comes from the superposition principle, which in turn originates from the homogeneous and linear properties of the Schrodinger equation.
Quantum entanglement exists not only in well-prepared lab-based experiments, but also in various phenomena in nature. Particles produced at the black hole's horizon are entangled. Subhorizon modes and superhorizon modes of inflationary perturbation are entangled. Quantum system can also be entangled with quantum time as it evolves.
I'm interested in exploring the fundamental natures of quantum entanglement, as well as their applications in black hole physics, cosmology, high-energy physics, and the nature of space and time.
Ngo Phuc Duc Loc, "Insights of quantum time into quantum evolution", arXiv:2306.11675
Ngo Phuc Duc Loc, "Time-system entanglement and special relativity", Mod. Phys. Lett. A 39, 2350183 (2024)
Ngo Phuc Duc Loc, "Unitary paradox of cosmological perturbations", Int. J. Mod. Phys. D 32, 2350050 (2023)