Three-Way Entanglement Results Hint at Better Quantum Codes

The physicists who won the prize proved one of the most counterintuitive realities of the quantum world. Even if the particles are separated, they must be considered a single system. The system you have in front of you can be affected by something thousands of miles away.

Computer scientists can make uncrackable codes byanglement and nonlocality. Two people are given a pair of particles that are entangled in a device. The particles can be used as a code to keep communications safe from quantum computers. Why don't you stop at two particles. There is no upper limit on how many particles can be in a single state. Physicists have dreamed of three-way, four-way, or even 100 way quantum connections for a long time. A lab in China has achieved what appears to be nonlocalentanglement between three particles at the same time, potentially boosting the strength of quantum cryptography and the possibilities for quantum networks generally.

Two-party nonlocality is crazy enough, according to a quantum information theorist. When you have three parties, quantum mechanics can do a lot more.

Physicists have entangled more than one particle. Depending on who you speak to, the record is between 14 particles and 15 trillion. These were only a short distance apart. The high bar for demonstrating nonlocality is what scientists need to make multiparty entanglement useful for cryptography.

To prove nonlocality, you need to know if the properties of one particle match up with the properties of the other. A particle that is still close to its twin may emit radiation that affects the other. If they are a mile apart and measured in a matter of seconds, then they are not linked by anything else. The experimenters used a set of equations called Bell inequalities to rule out other explanations.

There are more possibilities to rule out than with three particles. The scientists have to jump through a lot of hoops to prove the nonlocal relationship of the particles. The technology to create just the right conditions in the lab is needed.

The team in Hefei made a huge leap forward in the results published in August. They shot lasers through a special type of crystal and placed them in different parts of the facility hundreds of meters apart. They simultaneously measured the random properties of each photon. Three-way quantum nonlocality was found to be the best explanation of the relationship between the three particles. It was a complete demonstration of nonlocality.