Quantum Computing For Computer Scientists

Quantum computing is coming, so a lot of people are trying to articulate why we want it and how it works. Most of the explanations are either hardcore physics talking about spin and entanglement, or very breezy and handwaving which can be useful to get a little understanding but isn’t useful for applying the technology. Microsoft Research has a video that attempts to hit that spot in the middle — practical information for people who currently work with traditional computers. You can see the video below.

The video starts with basics you’d get from most videos talking about vector representation and operations. You have to get through about 17 minutes of that sort of thing until you get into qubits. If you glaze over on math, listen to the “index array” explanations [Andrew] gives after the math and you’ll be happier.

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Flawed Synthetic Diamonds May Be Key For Quantum Computing

If you’ve followed any of our coverage of quantum computing, you probably know that the biggest challenge is getting quantum states to last very long, especially when moving them around. Researchers at Princeton may have solved this problem as they demonstrate storing qubits in a lab-created diamond. The actual publication is behind a paywall if you want to learn even more.

Generally, qubits are handled as photons and moved in optical fibers. However, they don’t last long in that state and it is difficult to store photons with correct quantum information. The impurities in diamonds though may have the ability to transfer a photon to an electron and back.

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Wired and IBM Explain Quantum Computing to Students from Grade School to Grad School

Have you ever heard the old axiom that if you want to design a simple system, ask yourself if your grandmother could use it? Maybe that was on Wired’s mind because they asked a quantum computing expert — particularly IBM’s [Dr. Talia Gershon] — to explain what exactly quantum computing is at 5 levels. In the video they shot, which you can see below, [Dr. Gershon] talks to a younger child, a teenager, an undergraduate computer science student, a graduate student, and then a physicist.

We enjoyed some of the analogies of spinning pennies and the way she was able to bring the topic to an appropriate level for each of the participants. Truthfully, the final segment with the physicist ([Dr. Steven Girvin] was more of a conversation than an explanation, but it was interesting to hear his views on fault tolerance and how likely certain things were to occur in the near future.

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Simple Quantum Computing in 150 Lines of Python

What does it take to build a quantum computer? Lots of exotic supercooled hardware. However, creating a simulator isn’t nearly as hard and can give you a lot of insight into how this kind of computing works. A simulator doesn’t even have to be complicated. Here’s one that exists in about 150 lines of Python code.

You might wonder what the value is. After all, there are plenty of well-done simulators including Quirk that we have looked at in the past. What’s charming about this simulator is that with only 150 lines of code, you can reasonably read the whole thing in a sitting and gain an understanding of how the different operations really affect the state.

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Google Ups the Ante in Quantum Computing

At the American Physical Society conference in early March, Google announced their Bristlecone chip was in testing. This is their latest quantum computer chip which ups the game from 9 qubits in their previous test chip to 72 — quite the leap. This also trounces IBM and Intel who have 50- and 49-qubit devices. You can read more technical details on the Google Research Blog.

It turns out that just the number of qubits isn’t the entire problem, though. Having qubits that last longer is important and low-noise qubits help because the higher the noise figure, the more likely you will need redundant qubits to get a reliable answer. That’s fine, but it does leave fewer qubits for working your problem.

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Microsoft Quantum Simulator Goes to Linux and Mac

Everyone seems to be gearing up for the race to be the king of quantum computers. The latest salvo is Microsoft’s, they have announced that their quantum simulator will now run on macOS and Linux, with associated libraries and examples that are now fully open source. They have produced a video about the new release, which you can see below.

Microsoft also claims that their simulator is much faster than before, especially on large simulations. Of course, really large simulations suffer from memory problems, not speed problems. You can run their simulator locally or on their Azure cloud.

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Quantum Searching in Your Browser

If you’ve made it through the last two posts on quantum computing (QC), then you’ve seen the Quirk simulator, a little of IBM’s web-based offering, and how entanglement and superposition can do strange and possibly wonderful things. However, the superdense encoding I showed you didn’t really feel like a real computer algorithm. This time we will look at Grover’s algorithm which is often incorrectly billed as an “unstructured database search.” In reality, it is an algorithm for making a state — that is a set of qubits — match some desired state without simply setting the state.

By analogy, consider a web service where you guess a number. Most discussions of Grover’s algorithm will tell you that the service will only tell you if the number is correct or not. If the number was from 1 to 16, using traditional computing, you’d have to query the values one at a time to see which is correct. You might get lucky and hit the first time. Or it might take 16 times. With qubits you can get the same result in only four attempts. In fact, if you try more times, you might get the wrong answer. Of course, what you really get is an answer that is probably correct, because that how QC works.

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