Quantum entanglement is one of the uber-bizarre phenomena seen when things get itty-bitty, or inside the quantum realm. When two or more particles link up in a certain way, no matter how far apart they are in space, their states remain linked. That means they share a common, unified quantum state. So observations of one of the particles can automatically provide information about the other entangled particles, regardless of the distance between them. And any action to one of these particles will invariably impact the others in the entangled system. [1]

Figure 1. A key role for quantum entanglement

Figure 1 shows when researchers study entanglement, they often use a special kind of crystal to generate two entangled particles from one. The entangled particles are then sent off to different locations. For this example, let's say the researchers want to measure the direction the particles are spinning, which can be either up or down along a given axis. Before the particles are measured, each will be in a state of superposition, or both "spin up" and "spin down" at the same time.

If the researcher measures the direction of one particle's spin and then repeats the measurement on its distant, entangled partner, that researcher will always find that the pair are correlated: if one particle's spin is up, the other's will be down (the spins may instead both be up or both be down, depending on how the experiment is designed, but there will always be a correlation). Returning to our dancer metaphor, this would be like observing one dancer and finding them in a pirouette, and then automatically knowing the other dancer must also be performing a pirouette. [2]

The key is a secret

Secure communication is all about keeping information private. It might be surprising, therefore, that in real-world applications large parts of the transactions between legitimate users are played out in public. The key is that sender and receiver do not have to keep their entire communication hidden.

Culmination of years of work

The scale of the challenge is reflected in the breadth of the team, which combines leading experts in theory and experiment. The experiment involved two single ions -- one for the sender and one for the receiver -- confined in separate traps that were connected with an optical-fibre link. In this basic quantum network, entanglement between the ions was generated with record-high fidelity over millions of runs. [3]

References:

1. https://www.livescience.com/what-is-quantum-entanglement.html
2. https://scienceexchange.caltech.edu/topics/quantum-science-explained/entanglement
3. https://www.sciencedaily.com/releases/2022/07/220727124104.htm

Cite this article:

Thanusri swetha J (2022), A key role for quantum entanglement, Anatechmaz, pp.71