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Fundamentals

01 /Quantum computers with magical advantage? 02 /Bra-ket notation 03 /Born rule 04 /Bloch sphere 05 /Measurement operators 06 /Experimental and theoretical measurements 07 /How to measure in any basis 08 /State decomposition 09 /Why every maximally entangled state is secretly a Bell state 10 /Coherence 11 /Relaxation 12 /Quantum materials: the environment of a qubit 13 /Introduction to quantum error correction (QEC) 14 /Multiqubit systems 15 /Multiqubit gates 16 /Entanglement 17 /Measuring multiqubit systems 18 /Superdense coding 19 /Teleportation 20 /Entanglement swapping

Introduction to quantum error correction (QEC)

There are many ways to transport information. For example, you can send letters via a pigeon, use a USB stick to transport data between computers, or use a flashlight to say “hello” using Morse code. However, as you might expect, not all these communication channels as equally fault-proof. Many channels introduce some errors in your message. Luckily, there are several ways to account for such errors.

Postdoctoral researcher Ben Criger (QuTech) introduces one way to account for errors. To keep things simple, we will consider sending single “bits” of information, as bits eventually are entirely scalable to more complex messages. While this video will not (yet) cover any quantum material, it will prove that error correction is a vital component in many quantum algorithms and applications.

 

Quantum communication channels are a bit more complicated: apart from bit-flip errors, you can also encounter sign-flip errors. Watch this video to learn from Ph.D. student Jonas Helsen (QuTech) about this type of error and what it means for the research field that tries to deal with them: Quantum Error Correction (QEC).

 

 

Further thinking

  • Suppose you want to send a single-bit message on a channel from which you know that the bit-flip error probability p = 0.25. How many repetitions are required to have a 99% that your message is received correctly? 

  • You might have already heard about X, Y, and Z gates on single quantum bits, and that effect on their quantum state. In the field of Quantum Error Correction, we associate bit flips with X gates, as it turns a qubit from |0> into the |1> state. With what gate do you think we associate sign-flip errors? And why?

Solution

Further reading

The concept introduced in this video can be seen as the basics for similar schemes in quantum computing: quantum error correction (QEC). While it works roughly the same, the quantum version has an extra twist to these schemes. If you want to learn more on quantum error correction:

  • The wikipedia page on QEC gives a brief in-depth introduction to the subject.