In a recent study published in the journal Physical Review X, an international team of physicists from Austria, Scotland, Canada, Finland and Germany have demonstrated how quantum entanglement can be strengthened to overcome particle loss or very high levels of noise, which are inevitable in real-life applications outside the laboratory. This strengthening is accomplished by departing from commonly used two-level quantum bits, or qubits. Qubits are bi-dimensional systems, the quantum analogue to the classical bit, with values zero or one. In this study, the researchers instead employed entanglement of systems with more than two levels. By entangling particles of light through their spatial and temporal properties, scientists have now observed the survival of quantum entanglement under harsh environmental conditions for the first time.

https://phys.org/news/2019-12-entanglement-long-distance-free-space-quantum.html

https://physics.aps.org/synopsis-for/10.1103/PhysRevX.9.041042