What Is Quantum Computing?
Ask Science chats with Tech Talker about quantum computers. What are they and how can they change our world? Click to read or listen.
Lee Falin, PhD
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What Is Quantum Computing?
This week I’m teaming up with Tech Talker to discuss quantum computing..
First off, just what makes a quantum computer a quantum computer? I’ll let Tech Talker explain:
Tech Talker: It’s quantum…duh! Okay but seriously, a normal computer uses bits (1’s and 0’s) which are generally stored on transistors. Normal computers use bits to execute code, store pictures, play music, check Facebook, and pretty much everything you can think of. Quantum computers store their information as Qubits or Quantum Bits. Quantum bits are pretty tricky, because they can be a 0, or a 1, or both!
This allows for some pretty exciting things in the world of programming and mathematics.
Ask Science: What allows quantum bits, or qubits, to behave this way is something called superposition, which is one of the key principles behind the idea of quantum computing. A common object that we use as an example when we discuss superposition is the electron. Electrons have a property called spin, which can be either up or down. However, according to the theory of quantum mechanics, not only can an electron spin up or down, it can also have a spin that is any linear combination of those two states. A linear combination means that it’s a little of the up state plus a little of the down state.
Where things get strange is that while one observer may see the electron with an up spin, another observer might see the electron with a down spin. The fact that these differences of measurement occur, even though both observers are looking at the electron at precisely the same moment, means that in quantum mechanics we consider the electron to have both of these spins at the same time. We call this property superposition.
This is important for quantum computing because, as Tech Talker said, normal computers use a bit which can either be 1 or 0. So if you have an 8-bit computer, it can have 1 out of 2 to the 8th power (or 256) at any given time. However a quantum computer taking advantage of superposition could be in all 256 of these states at the same time. That means that for certain types of algorithms (though not all), quantum computers could cause an enormous increase in computing power.
So what exactly is a qubit?
Just like a regular computer can represent a regular bit using various methods (for example the way it stores bits on your hard drive, a DVD, and a RAM chip are all different), a qubit can be represented by different things. As I already mentioned, electrons make good qubits, as do photons, and atomic nuclei. In fact, any object that has quantum properties can be used as a qubit. You can see a complete list here.
Entanglement tells us that two particles can be connected in a way that if you measure the state of one particle, you instantly know the state of the other.
TT: Quantum computers use this breakdown of the superposition to do some really interesting calculations that normal computers have a really hard time figuring out.
For example, it’s really hard for normal computers to find factors of prime numbers, and it just so happens that almost all cryptography uses some form of large prime numbers or one way functions to secure your data.
EE: Now, because each of these qubits can exist in all of their states at the same time, you might wonder how you could use these things to store any information. In order to do so, we need to take advantage of another property of quantum theory called entanglement.
Entanglement tells us that two particles can be connected in a way that if you measure the state of one particle, you instantly know the state of the other particle as well, regardless of the distance between those two particles. This has several implications in quantum computing, but one of the most important is that it lets us entangle the qubits of our quantum computer together so that once we know the state of one, we can also know the state of all of the others.
So with these two principles, a quantum computer can perform calculations so quickly, that computing problems that used to be considered impossible to solve in a resonable amount of time, could be calculated extremely fast. For example, a quantum computer using the right algorithm could break strong cryptography relatively easily. So just how close are we to replacing our smartphones with quantum computers?
TT: Now don’t worry just yet. So far, there are only quantum computers that use a few qubits to do very simple computations. In the future though, this may lead to some really interesting shifts in technology!
Conclusion
So there you have it, quantum computing in a nutshell.
If this all sounds a bit muddled, don’t worry. Even scientists that have been instrumental in the development of the field haven’t found it very intuitive. Niels Bohr said “…those who are not shocked when they first come across quantum theory cannot possibly have understood it.” And Richard Feynman said “I think I can safely say that nobody understands quantum mechanics.”
Speaking of quantum coolness, my new middle-grade science fiction novel, Half Worlder, is now available for sale on Amazon for just $2.99. Plus, throughout the month of December, half of the proceeds go toward the I Love Lucy project, a super cool fundraiser that is campaigning to raise money to support research on Bardet-Biedl Syndome, a genetic condition which can lead to blindness in thousands of children. You can find more information on the fundraiser here.
So pick up a copy of Half Worlder for the sci fi fan on your holiday list today!
Quantum image courtesy of Shutterstock.
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