And now we get to the big things. I’m not looking at the bits and bobs that are used to build the technologies anymore. It’s going to be a nice shift.
If you are looking for a popular science style article but longer, read about superposition and entanglement first and come back.
So what is quantum computing? The popular science answer is something like this:
Quantum Computing is a method of Computing that uses qubits instead of bits and leverages the powers of entanglement and superposition to perform godlike calculations before you even think of them.
Yah. That looks right. Some may mention multiverses and (un?) alive cats. But top hat wearing triangles in the sky telling us to stay weird are not typically expected.
Computationally complete gateset
I hope that if you read my other posts, specifically about entanglement, you might have some idea about how quantum computing can exist.
Conceptually it’s just an XOR with a wire carrying one input further.
If you know about classical logic gates, you’ll recognize that an XOR and therefore a Cnot is classically computationally complete. There are definitely other parts that could be useful for computing, but you can construct them from that one part. (More on this later)
The same isn’t quite true of quantum computing. These devices have three continuous ranges of motion rather than one extremely constrained one. We also need to be able to traverse these.
A computationally complete gateset then also has rotations around the X,Y and Z axes. These are typically written as something along the lines of RX, RY and RZ.
To summarize, arbitrary rotations and entanglement gives us a complete gateset for every quantum computation needed.
Helpful additions
Now, a Cnot may be computationally complete, but we don’t typically just use that. It’s a lot easier to use NOTs, ORs, ANDs etc.
In the same way we have gates constructed of these arbitrary rotations and Cnots, examples include X (not or bit flip) gates, Toffoli (Ccnot) and hadamard gates (which have no digital analog)
Sorry, no code examples…. That’s just too much.
You may remember in previous posts I shared code examples. In this case it’s way too much so I’ll cover use cases.
- Factoring large numbers
- CFD
- Simulating large molecules
- Simulating small molecules
- Simulating large scale systems
- Simulating universes
- Creating and potentially destroying millions if not billions of alternate universes every time a wave function is collapsed (and trust me there’s a lot of those) and these universes are so similar to this one that instead of being a tool to alleviate the suffering of you 3d meat creatures by exponentially speeding up calculations instead it exponentially increases the amount of you and therefore the suffering! Hope you are in the good timeline kids!
Uh. Ok then. That was odd.
How about I let Quantum Zoo list algorithms for you? I’m not sure how many algorithms are in there, but there were 497 citations and from my estimate that’s pretty close to the number of algorithms listed. I imagine there’s many many more, since there are more classical algorithms and quantum is an extention of classical in many ways.
What types of computers exist?
There are a lot of different types of quantum computers. It’s very unlike the classical computing industry which is absolutely dominated by silicon chips. There is so much research in this area and each one has their own pros and cons.
I’m not sure this is truly accurate but in my observations, academics likes photonic computers and big industry (IBM, Google, etc) prefer superconducting, specifically transmon qubits. It’s the startups and smaller clouds that are playing with other ways of making quantum computers. I can’t cover all of these, perhaps in a series.
I’d say the majority are compatible with qiskit and the superconducting computers all are. Qiskit is truly the best way to get started, but with the recent update to qiskit 1, it’s broken a lot and had made me not want to write code for you that you can just plug and play. You might want to learn qiskit to learn quantum computing but find something more stable for production.
Perhaps one day I’ll write one of these on the different qubit modalities. But I feel this is more in the wheelhouse of Brian N. Siegelwax who has done a lot of work in that area.
Im honestly not sure how to end this and theres more I could say but its feeling a little off topic from the goal of this post, so as Bill Cypher says…
Remember! Reality is an illusion, the universe is a hologram, buy gold, bye!
