When two or more systems are created or interact in such a way that the quantum states of some cannot be described independently of the quantum states of the others, scientists are studying quantumentanglement. Even though the systems are separated, they are still linked. There's a lot of potential for applications in quantum computing. The systems becomeentangled when they interact with their surroundings.
A light source that produced two entangled light beams was developed by the Laboratory for Coherent Manipulation of Atoms and Light at the University of So Paolo. Their work is in a journal.
The light source was made up of a non- linear optical response crystal between two mirrors and is called an optical parametric oscillator. When a bright green beam shines on the apparatus, the crystal-mirror dynamics produce two light beams with quantum correlations.
Light emitted by crystal-based OPOs cannot interact with other systems of interest in the context of quantum information since its wavelength is not the same as those of the systems in question. In the past, our group has shown that atoms can be used as medium instead of a crystal. In order to get a source that could interact with other systems with the potential to serve as quantum memory, we obtained a source that was based on rubidium atoms.
This wasn't enough to show the beams were not connected. The beams' phases needed to show quantum correlations as well as the intensity. He said that they achieved that in the new study.
New detection steps allowed us to measure the quantum correlations in the fields generated. They were shown to be entangled. The detection technique allowed us to see that the structure was richer. Instead of two adjacent bands being entangled, what we produced was a system of four entangled bands.
The waves were entangled. This is important in a lot of protocols. This type of light source could be used in other ways. The reduction of intensity fluctuations can enhance the sensitivity of optical sensors. Imagine a party where everyone is talking, but you can't hear anyone else. You can hear what someone is saying from a distance if the noise is reduced enough.
The alpha waves emitted by the human brain can be measured using atomic magnetometers.
Rubidium OPOs have an advantage over crystal OPOs according to the article. The use of an atomic medium in which the two beams are produced more efficiently than with crystal avoids the need for mirrors to imprison the light for such a long.
Other groups tried to make OPOs with atoms but failed to show quantum correlations in the light beams. There was no limit in the system to stop this from happening. The temperature of the atoms is important for observing quantum correlations. He said that higher temperatures prevented the researchers from observing correlations.
There is more information on Continuous Variable ENTanglement in an Optical Parametric Oscillator Based on a Nondegenerate Four Wave Mixing Process. There is a book titled "PhysRevLett.129.163601."
Journal information: Physical Review Letters
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