Wait What? Teleportation Exists?
Let me tell you something:
I seriously hate commuting.
Walking, biking, driving, etc - I don’t like it because it’s SO time consuming (not that I can drive yet, but still 🤠 ).
I’ve always wished that I could teleport myself so that I wouldn’t have to trudge all the way downstairs to grab a snack, or endure the long drives to school.
When I first thought of teleportation, I imagined this really wacky ‘sci-fi space-time continuum’ thing. But I then realized that teleportation does exist today.
Kind of.
Quantum Teleportation
There are three main kinds of teleportation:
- Instant teleportation because of some force or magic
- When the object being teleported is disassembled, and the pieces are teleported
- The object is scanned, and instructions for recreating the original object is transferred (hint: this is the essence of quantum teleportation!!)
Okay, okay, okay. Quantum teleportation won’t help us get food faster (beam me up, Scotty!!), but it will help us transfer quantum information.
Doesn’t sound exciting? Let me break it down for you!
A Brief Overview of Quantum Computing
If your quantum computing fundamentals are a little rusty, and you need a little (qu)bit of review, I highly recommend you watch this video:
A TL;DR on the key points from this video:
- Classical states are binary (aka 1 or 0), while quantum states can be in 1, 0, or a superposition state of somewhere between 1 and 0
- Although we can do calculations and make estimates, we’ll never know the exact state of the superposition, because upon measurement, the state will collapse into 1 or 0
- Two entangled qubits are connected, and information about one state will tell you something about the other, even if there’s an entire universe between the two states
One more thing that wasn’t talked about in the video:
If we were to write out the equation of a state, |Ψ>, this is what its equation would look like:
|Ψ> can be described by an α probability of it being in |0> plus a β probability of it being in |1>. All superpositions can be described with this equation.
So when we say that we’re transferring quantum information, we’re actually just transferring the values of α and β. But if you remember from the video, we don’t know the true values of α and β. So how does quantum teleportation really work?
Quantum Teleportation Protocol
I have a state |Ψ> that I want to send you. Unfortunately, I can’t perform some kind of a ‘CMD-C, CMD-V’ operation because although classical states can be duplicated, states in superposition can’t be cloned (more on this later!!)
Along with qubit |Ψ>, I also have another qubit |A>. And you have a qubit |B>.
|A> and |B> are very special and are known as EPR pairs. This means that both qubits are entangled in such a way that upon measurement, they would collapse into the exact same states.
Think of EPR pairs as a literal example of ‘mi casa, su casa.’ If something happens to the first qubit, it’ll have the exact same result on the second qubit.
#theProcess
I would first start by completing a Bell Measurement on |A> and |Ψ>. The process of doing this involves a CNOT and a Hadamard gate.
The end result of this would be 1 of 4 states — 00, 01, 10, or 11. These are classical states, and can thus be encoded within 2 classical bits. I then take the bits and send them to you through a classical communication channel.
On your end, |B> also is in 1 of 4 states, except these states are different superpositions. Of the four, only one of them matches with the original state of |Ψ>. The remaining three are closely related to |Ψ>.
Based on the values of the classical bits, you would perform a different operations to identify which of the four states |Ψ> was originally in.
After applying (or not applying) these operations on the second EPR pair, |B> would transform into the exact same state that |Ψ> was originally in, therefore ‘teleporting it.’
But Wait … what happened to |Ψ> and|A>?
Well ….. both qubits were destroyed.
Destroyed?
Yup. Because of something called the no-cloning theorem, you can’t create an independent and identical copy of an unknown quantum state. But this doesn’t include entangled qubits like the EPR pairs.
But Why Teleport Quantum Information?
Even though quantum teleportation won’t help us teleport Star-Trek style, advancements in this subset of quantum computing could pave the way for advancements in security, communication and internet industries.
In 2017, Chinese and Austrian scientists established a quantum-secure connection for a video conference (Zoom who? I only do quantum video calls ;). They transferred information using photons through China’s Micius satellite, which is highly sensitive and could detect the quantum states of individual photons from the ground. Reseachers in Austria and China could access a shared quantum key, which allowed them to participate in a quantum-encrypted video call.
Another huge application of quantum teleportation is a super fast and super secure quantum internet. Because particles are entangled, information is transferred instantly- equivalent to the speed of light. Implementing a quantum internet system requires some very expensive infrastructure to both develop and implement the technology.
The biggest advantage of quantum communication and internet is the enhanced security. Upon unrequited third-party involvement, the system would entirely break down, which shows the potential for essentially an unhackable solution to many of the problems we face today.
Resources:
- How to Teleport Schrödinger’s Cat by MinutePhysics
- The No-Cloning Theorem by MinutePhysics
- Quantum Teleportation from the Qiskit Textbook
- The Applications and Challenges of Quantum Teleportation doi:10.1088/1742–6596/1634/1/012089
- Quantum Teleportation: Paving the Way for a Quantum Internet by ProjectQ Sydney
- Quantum teleportation and Bell States
