Quantum Logic: What is it?

So over the weekend I was redditing and I found an article which described Oxford University researchers achieving a quantum logic gate with 99.9% precision. Being the ever curious redditor I am, I clicked the link to learn more about what a quantum logic gate is. Turns out, it’s pretty huge.

Quantum logic? What is this black magic?

I wish there was a less technical way to explain quantum logic, but it does take a fair knowledge of physics to fully understand the details but I’ll try to make it as easy as possible. In quantum mechanics, an entity exists in superposition until observed. What this means is that it exists in both states (in our case, 1 and 0) until it is observed. When it has been observed, it collapses into one of two states. Some of you may be familiar with Schrodinger’s Cat. This is an example of quantum mechanics. The moment you open the box, you either have an angry cat, or a dead cat. You could say by opening the box you killed the cat.

How does this relate to computers?

The simplest way to describe a logic gate is a switch that is open or closed depending on whether the data entering is a 1 or a 0. There are billions of these gates in your CPU making all the decisions for you based solely on 1’s and 0’s. This is great everyone knows this. But where quantum logic differs is that we no longer work with bits, but qubits. A qubit is identical to a bit, except it exists as both a 1 and 0 at the same time. A regular string of 4 bits can produce a total of 16 different outcomes, of which it can only be one. A string of 4 qubits can also produce 16 different outcomes, but it exists as all of them at once. This value goes up exponentially as you add qubits. Another mind bending property of qubits is quantum entanglement. As long as you can determine which other qubits are connected, you can find out everything about entangled qubits by only observing one. Don’t ask me how this works I never got to quantum mechanics in physics class. Apparently by exploiting the properties of quantum entanglement you can determine which of these 16 combinations is the correct one to a very high confidence. Below illustrates quantum vs standard.

By exploiting quantum entanglement, we can narrow down the choice to a very small amount, thereby only needing to test a few of the combinations, rather than all of them.

This only scratches the surface of what quantum computing can do. I can see very attractive opportunities for extremely large datasets being manipulated with quantum computing to cut down on time to search through. Thats SO many SQL queries at once! I wonder if theres a QuantumSQL database available…