Quantum Teleportation
- Maggie Swanson
- Aug 12, 2023
- 3 min read
When you think of teleportation, you probably think of the teleportation of physical things, like humans. Unfortunately, we are a long ways off from a world where you could teleport from your house to work or a vacation spot in mere seconds. However, quantum teleportation is happening right now!
What is it?
Quantum teleportation uses the quantum principle of entanglement, which is where two individual things (photons, electrons, etc) can be entangled so they share the same quantum state. Think of it as two individuals facing each other with a wall in-between them so they can't see one another. One person waves at the other person. Without seeing the person waving, the other person knows they are being waved at. This is the idea of entanglement, where two things share this connection across any distance or barrier.
Now, imagine you have two friends Alice and Bob. Alice receives a secret code in an envelope to send to Bob. However, she can't send that envelope through the mail because it might be intercepted. How could she still get Bob that information?
What if Alice and Bob were entangled? Meaning if something happened to Alice, such as she changed her hair color, started playing the guitar, etc, Bob would know. Think of the people waving example. So, if Alice could somehow change herself based on the code, Bob could decipher it. Once reading the code, Alice picks up the phone to call Bob to say she has dyed her hair red. With this information, Bob can decipher the code without ever having to see the envelope.
This is the basic principle of quantum teleportation; the fact that information can be shared by tracking its interaction with two entangled things rather than sending the physical information itself between them. Think about it, it is much more difficult to decipher the code if the only information sent over the phone line was that Alice now has red hair. It gives no information about Alice's original state and what about the code made her change. That change is only something Bob can understand because of the special properties of their entanglement.
Getting into the Science
That is the basic idea of quantum teleportation, but it isn't happening with Alice and Bob or secret codes. Instead, you have two entangled particles A and B a distance apart from each other (locations 1 and 2) and want to transfer information C. These particles and information are stored in separate qubits (A, B, C). The goal is to be able to transfer information C from location 1 and 2 without sending it physically across a network that can be intercepted. This can be done by using particle A and B's properties of entanglement.
Locations 1 and 2 host the two entangled qubits A and B. At location 1 you have information C which can be entangled with A by measuring the Bell State of the two of the,. The measurement is a complicated mathematical process that can convert two qubits in superposition (think of a quarter spinning between heads and tails), into something that is binary (heads or tails). This converts the qubit (superposition between 0 and 1) into a classical bit (0 or 1). This process has successfully translated the effect that information C had on A into bits that can be sent over a classical computing network. Relating back to the Alice and Bob example, if Alice is qubit A she has just read the secret code (C) and that interaction caused some sort of change. Her calling Bob to report the change is the same thing as the bits now being sent over the classical computing network.
Ok, now these bits are being sent over a classical computing network. This is the only step in quantum teleportation that takes a large amount of time (compared to the rapidness of the Bell State measurement). When scaling quantum teleportation, this time frame is a big factor in large-scale application. Once the bits are received by qubit B at location 2, B can decipher the bits to figure out what the interaction was between A and C (using the properties of entanglement). This change means qubit B can reconstruct what information C was without having to send it explicitly over the classical network.
Why Should I Care?
Although it won't cut down on commute times, quantum teleportation is a massive step towards more secure information networks. With it, information can be transferred through tracking changes to un-hackable states (entangled qubits in superposition), rather than sending it explicitly over a network that can be intercepted.
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