How Quantum Computing Can and Can’t Help Us Here in Macro World

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In last week’s podcast, “Enrique Blair on quantum computing,” Walter Bradley Center director Robert J. Marks talks with fellow computer engineer Enrique Blair about why quantum mechanics is so strange, yet an intrinsic part of the way our universe works. They discussed whether quantum computing will be in our future any time soon? In our cell phones? What difference will it make?

The discussion of quantum computing begins at approximately 37:31. The Show Notes and transcript follow.

One significant thing that quantum computing could do is enable more secure encryption.

Robert J. Marks: Let’s get to quantum computing. This is the thing that’s in the news everywhere. There was the announcement that Google has built a quantum computer that has achieved quantum supremacy. What is quantum computing, for a layperson?

Enrique Blair (pictured): Quantum computing uses quantum systems to process information in a way that our classical computers can’t. Classical computers use “bits,” which stands for binary digits. A binary digit can be either zero or one. That’s it, zero or one. Now quantum computing uses quantum bits. So you don’t just have just zero or one; you have these quantum superpositions of zero and one.

With quantum superposition and entanglement, you can process information in ways that you can’t classically. The great hope and the great promise there is that quantum computers can process certain things and do certain calculations efficiently that you can’t do on a classical computer. There are some well known examples of this. The best known is Shor’s algorithm.

That is all about defeating a very widely used form of encryption. This requires factoring very large numbers into two prime numbers.

Robert J. Marks: Okay. That’s one of the things that a quantum computer can do. We have Shor’s algorithm, which is going to make all decryption obsolete.

Enrique Blair: Yeah, that’s why governments are so interested in pouring hundreds of millions of dollars into this sort of research.

Robert J. Marks: In fact, both countries and companies are battling to get quantum computers. My understanding is that these different companies are using different quantum mechanisms. Not everybody is using the same approach because quantum exists everywhere, no matter what material you look at.

They’re all looking at different sort of quantum materials. Now the good news is, which I hope we can talk about in a little bit is that once we get this Shor’s algorithm running and we get all the commonly used decryption made obsolete, we can actually use quantum mechanics to do quantum encryption and actually have something which Shor’s algorithm can’t crack. That’s the good news in the future, is that right?

Enrique Blair: That’s right. While quantum computing could take away our RSA encryption scheme, quantum communication could give us something that’s provably secure.

The news about quantum laptops isn’t so good.

Robert J. Marks (pictured) Will our laptops and our computers ever operate totally on a quantum mechanics principle? Or is quantum computing kind of a separate way of doing things and doesn’t relate to the sort of computing that we do on our computers today.

Enrique Blair: Quantum computing certainly is very powerful. And in theory, quantum computers could do everything that classical computers can do and more. However, quantum computing is so expensive that it’s really not feasible and it won’t be for the foreseeable future to have quantum computers on our laps or in our cell phones.

To get many qubits working together, you really have to isolate them from the environment because of decoherence (the quantum system settles on one state). To isolate them from the environment, we need specialized equipment like dilution refrigerators which are massive and use a lot of power.

Quantum computers feature superconductivity (the “ability of some metals to exhibit a zero resistance at low temperatures”) so they also have to be kept really cold.

Enrique Blair: In the Google article about quantum supremacy, they had to cool their system down to 20 millikelvin.

Now, 20 millikelvin is nearly absolute zero. That’s where nothing vibrates. If you have heat, things vibrate. And as you reduce the temperature, the vibration slows down. At zero degrees Kelvin, there would be no vibration at all.

Enrique Blair: I don’t want that on my lap.

Robert J. Marks: Okay. Yeah, hopefully they can get something which operates at room temperature. Do you know if there’s any research going on now where things are working at room temperature?

Enrique Blair: Well, that’s a good question because there are a lot of different ways to implement qubits. Maybe you have a diamond crystal and you pull out a couple carbons and put in a nitrogen, this gives you a nitrogen vacancy center.

In theory, you can manipulate qubits that are based on these nitrogen vacancy centers. You can manipulate them and read them at room temperature. But if I’m not mistaken, I think even still you have to cool them down so that you get high fidelity readings.

I’m studying more about these NV centers and maybe more cost effective ways to make them, because a diamond’s simply expensive. There are candidates for room temperature quantum computing.

Next: Why Google’s “quantum supremacy” isn’t changing much in the computer world—not yet

Here are the earlier discussions:

“Spooky action at a distance” makes sense— in the quantum world. Einstein never liked quantum mechanics but each transistor in your cell phone is a quantum device. The fact that the spooky quantum world is real means that quantum computing could greatly reduce computers’ drastic environment impact.

The final ambiguous truth about Schrödinger’s cat. Schrödinger came up with the cat illustration to explain quantum mechanics to interested people who were not physicists. We don’t see quantum paradoxes outside the lab because everything we see consists of far too many quantum subsystems for any one particle to stand out.

How scientists have learned to work with the quantum world. It’s still pretty weird, though. Wave function mathematics can work with particles that may be in different places (quantum superposition). QM can also generate truly random numbers we can use.

Here’s why the quantum world is just so strange. It underlies our universe but it follows its own “rules,” which don’t make sense to the rest of us. Computer engineer Enrique Blair explains to Robert J. Marks the simple experiment that shows why so many scientists find the quantum world “mind-blowing.”