The Max Planck Institute for Quantum Optics reported on August 24 that it has achieved quantum entanglement of 14 photons, the largest number ever recorded.
Quantum entanglement—described by Albert Einstein as “spooky action at a distance”—is a phenomenon where two or more particles become intertwined in such a way that they no longer exist independently. A specific change in the properties of one particle leads to an immediate change in its partner, even when they are far apart.
Although science has yet to fully explain this phenomenon, experiments have confirmed that quantum entanglement truly exists and has even become the foundation for new technologies such as quantum computers, where entangled particles are used to store and process information. In computational terms, they are referred to as quantum bits or qubits.
To effectively utilize a quantum computer, a larger number of fundamental building blocks—technically quantum entanglements—are required to perform calculations. A team of physicists at the Max Planck Institute for Quantum Optics (MPQ) in Germany has demonstrated this task for the first time using photons emitted from an atom.
Using a new technique, the research team created up to 14 entangled photons in an optical resonator, which can be precisely and efficiently adjusted to specific quantum physical states. This method could facilitate the construction of powerful and robust quantum computers, while also serving future secure data transmission.
A rubidium atom trapped in an optical resonator consisting of two highly reflective mirrors. The repeated excitation of the atom generates a chain of entangled photons. (Photo: MPQ).
In the experiment, physicists placed a rubidium atom at the center of an optical cavity. With laser light of a specific frequency, the state of the atom can be precisely determined. They then used an additional control pulse to excite it, causing it to emit an entangled photon.
This process was repeated until the entire chain of photons was created, all entangled with one another. Between each emission, the atom was manipulated in a specific manner (rotated), helping to generate the entanglement of 14 photons.
“To our knowledge, 14 entangled light particles is the largest number of entangled photons produced in a laboratory to date,” emphasized co-author Philip Thomas at MPQ.
The research team also noted that this is the most efficient process ever developed, achieving nearly 50% efficiency.
“This means that almost every second of pressing the button to fire the laser at the rubidium atom will generate a photon that can be used for a specific application,” Thomas added. “Overall, our experiment has addressed a long-standing obstacle in scalable measurement-based quantum computing.”
Beyond quantum computing, the research may also advance quantum communication, where information is transmitted through optical fibers. The method developed by Thomas’s team will allow quantum information to be sent through entangled photons, ensuring secure communication, according to the press release.
The research findings were published in the journal Nature on August 24. In the next phase, Thomas and colleagues will continue working to generate photons from two atoms.
