Quantum Steering for everyone. The layman’s physics.

|Difficulty level: Easy|

Consider two people, Alice and Bob. They are really far apart, as far as you can imagine. Yes, that far! Now, considering they share a pair of particles, connected in some way which interacted mysteriously sometime in the past. But now they are in a kind of long-distance relationship. With that ‘layman’ background let’s hear this!

Alice makes some measurement on her part of the pair of particles. Bob also does similar independent measurements on his particle. Common sense says both of them should give independent results. Why? Because they are really far apart, such that not even light can send any signal to the other particle and influence instantly in any way. But, if the act of Alice making measurements on her particle can instantly change the possible outcomes on Bob’s side, it would be amazing.

In other words, and in the language of quantum physics, the ability of one party to steer the quantum state (and thus the possible outcomes of measurements) of the other party (particle) is known as Quantum Steering. Imagine this like moving the steering wheel on the driver’s seat actually changes the orientation(state) of the wheels in real. It’s similar, it’s just that in Quantum Steering there is no physical rod as in a real car and they can be galaxies apart. If you’ve heard of other crazy terms of the quantum world, I must tell you that Quantum Steering is not exactly the same as Bell non locality and Quantum Entanglement, although are very closely related.

I hope this gives you a very rough and layman’s feeling of this amazing feature of the quantum world. I will post a detailed version of this article on Quantum Steering, hopefully with minimum mathematics. There is a lot more to Quantum Steering. For a precise scientific feeling of this, stay tuned.