Ok, so I’ve heard a lot on this subject and I don’t know if some of it’s fake, or if it’s just a terminology problem but hoping someone can clarify. So I don’t have a great understanding of quantum computing, but I know some of the most common forms of encryption (RSA and Elliptic curve) are not quantum resistant. For ages I kept hearing “if quantum computing becomes realized, software systems around the world will break because anyone can decrypt anything not quantum resistant”.
My understanding was that IBM Quantum System One was the largest quantum computer with a measly 20 qubits which isn’t enough to implement shor’s algorithm on realistically large enough primes to break RSA. Now I hear that Majorana 1 has a million qubits but for some reason this isn’t causing global panic?
Then I read someone saying that it takes a large number of qubits to make what’s called a “perfect qubit”. What exactly does that mean? I’ve also heard that “topological qubits” are different to regular qubits. I do have a good understanding of quantum superposition if that’s necessary to make sense of all this hullabaloo.
Would greatly appreciate if someone could actually explain what all these science magazine clickbait articles are failing to.
Comments
>Now I hear that Majorana 1 has a million qubits
Well, you’ve heard wrong. It is still debated whether or not Majorana 1 has actually contained a single proper Majorana zero-mode which could then be used as a topological qubit.
The advantage of topological qubit is that if you can create them they should be more stable than other qubits, meaning it should be easier to scale up their number as decoherence is less likely with them. Note the several if’s and should’s in that statement.
>Majorana 1 has a million qubits
It has 8 qbits, all supposedly reliable/topological . It’s architecture is meant to theoretically scale up to 1 million qbits on a single chip. But so far, they only got 8.
Majorana 1 only has 8 qubits. The claim of 1 million qubits appear to be marketing hyperbole describing a potential setup of multiple Majorana 1 devices working together in a similar way that multiple regular CPUs in a multicore environment does. A practical way of actually doing this has not been developed yet, however.
> Then I read someone saying that it takes a large number of qubits to make what’s called a “perfect qubit”. What exactly does that mean?
It means you need a large number of physical qubits for every logical qubit. It’s usually hundreds. This is because qubits are very fragile. Their state can be destroyed very easily. When you put many of them together you can create error corrected qubits where the quantum state can be recovered if partially destroyed.
When they talk about needing a million qubits to break RSA, they are talking about logical qubits.