Quantum entanglement, an enigmatic connection between particles, serves as a crucial asset for quantum computing and communication, and in some instances, can be shared almost limitlessly.

Numerous quantum operations, including the secure transfer of encrypted quantum data and computations on quantum systems, depend on multiple entangled particles. Ujjwal Sen and his team at the Harish Chandra Research Institute in India have inquired whether entanglements can be shared rather than created anew.

“We imagined a scenario where someone possesses an abundance, like money or treats, willing to distribute it among children, employees, or others,” he explains.

To explore this idea, his team formulated a mathematical model featuring two hypothetical researchers, Alice and Bob, who share entangled particles. When additional researchers, Charu and Debu, require entanglement but cannot generate their own, the first pair must assist.

Their calculations indicated that if Charu’s particles interacted with Alice’s, and Debu’s with Bob’s, the initial pair could transfer part of their entanglement to the latter pair. Kornikar Sen, another researcher at the Harish Chandra Research Institute, clarified that although Charu and Debu couldn’t interact with each other, they could utilize a shared “entanglement bank.”

In fact, the researchers concluded that this procedure for sharing entanglement could potentially accommodate an infinite number of successive pairs of researchers unable to create their own entangled states. Ujjwal Sen expressed that this revelation was surprising, as they had not anticipated the ability to share entanglement across so many pairs when they commenced their calculations.

Moreover, the team pinpointed how the experimenters would need to modify their operations on the particles to facilitate this sharing mechanism, although these specific methods have yet to undergo experimental validation.

Chirag Srivastava from the Harish-Chandra Research Institute added that each new experimenter obtaining entanglement from Alice and Bob would acquire a diminishing share, as some entanglement dissipates during interactions.

Consequently, while the sharing methodology could theoretically continue forever, in practice, it would sooner or later cease when some researchers receive insignificantly small portions of entanglement.

How this situation unfolds—and how it measures against other methods by which researchers can obtain entanglement from a single source—remains to be explored through ongoing experiments.