Episode: 3027
Title: HPR3027: What is quantum computing and why should we care?
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr3027/hpr3027.mp3
Transcribed: 2025-10-24 15:25:07

---

This is Hacker Public Radio, episode 3,027, for Tuesday, 10 March 2020.
Today's show is entitled, What is Quantum Computing and Why Should We Care?
Quote,
It is hosted by Mike
and is about 25 minutes long
and carries a clean flag. The summer is
What is all the quantum computing hype about and what is it that quantum computers will be able to
do? Quote Dash!
This episode of HPR is brought to you by An Honesthost.com.
Get 15% discount on all shared hosting with the offer code
HPR15, that's HPR15.
Better web hosting that's Honest and Fair at An Honesthost.com
.
.
.
.
Greetings might be Mike here for Hacker Public Radio.
I'm here to talk to you about something a little different this time, quantum computing.
My goal here is to give you a sense for what it is, why we care,
why are governments spending so much money on it?
Is it hype?
Is it real?
Does it threaten the internet?
So I want to get into this without really getting in the weeds.
The way to really understand quantum computing is the math.
That doesn't work out too well in an audio podcast.
So we're not going to go into that level of detail.
But at a very high level I do want to paint the picture for those that just don't know much about it
and hear a lot of hype, a lot of excitement, and are not sure what to believe.
And we'll see how it goes.
Maybe I'll do subsequent episodes and get into a little more detail.
The goal of quantum computing is to take advantage of quantum effects
to do computation that can't be done by our conventional computers.
This idea really came from Richard Feynman in the 1960s
at the theoretical physicist in the US who thought about modeling quantum systems
and realized that we were just weren't going to be able to do a good job
unless we used those quantum effects to do the computations.
So what are quantum computers?
They're computers that take advantage of quantum effects.
Know that sounds like a circular argument, but there's two principal effects
that are used to great advantage in quantum computing to do amazing things.
So at a very high level I said what is a quantum computer?
It's a computational system that's taking advantage of quantum effects
to do things a classical computer cannot.
So what are those quantum effects and what are those things that it can do
that a classical computer cannot?
Well, there's two principal effects here and this is the most difficult material in this podcast.
So if you don't get it right away and it sounds weird, there's a reason for that.
There's a good reason. The reason is because it is weird.
It is strange. Nobody really understands it.
In fact, there's good reason to believe that we cannot ever fully know what's going on.
Nature won't let us look behind the curtain and actually see what is going on.
So that makes quantum mechanics in general and quantum computing specifically
kind of difficult to deal with at a conceptual level.
The solution is if you're getting involved in the space to rely on the math.
The math is clear even if the real underlying meaning.
What does it mean? Is anything but clear?
So those two quantum effects that I alluded to are entanglement and superposition.
Entanglement is that property that Einstein called spooky action added distance.
You can probably tell from that definition he wasn't that crazy about the idea.
If you take two particles and put them close to each other under the right conditions,
they will enter a state whereby they are inherently dependent upon each other.
What does that mean?
Well, let's go back to this idea of one particle first.
How it exists and how we interact with the particles.
So particles have properties and disapplies to everything from electrons and photons to smaller things and bigger things.
Anyway, let's use photons for our example here.
A photon you can measure properties about it such as the polarization.
But by doing so, in fact by any interaction with particles,
you've interfered with them and affected a change.
This is one of the really tricky bits about quantum computing.
Any interaction impacts the system and creates a change in the system.
Any interference whatsoever.
This is the reason I said you can't really look behind the curtain.
One of the properties the photon has is polarization.
If you think about a photon as a wave, it's oscillating, which means it's kind of wiggling back and forth.
The direction of that wiggling, it might be going up and down from your perspective.
It might be going from side to side horizontally.
The direction of that wiggling is called the polarization.
Now you've probably bought a pair of polarized sunglasses at some point in your life.
And what that is is a filter.
Think of it as a filter with little slits going straight up and down or sideways so that only some of the light gets through.
Other light is blocked.
There are crystals that you can get that will let a photon through or block it.
And you can interpret that as being a zero or a one.
And this is the whole idea in quantum computers.
We want to measure these quantum bits or qubits down to classical values of zero or one that we're used to using in computing.
That's useful.
Some superposition. There's that word again of zero and one.
Well, there are things we can do to it, but we need an answer.
We need a fixed deterministic output of zero or one.
So when our example of entanglement, we've got two photons.
You can measure things about one of the photons.
For example, the polarization that I mentioned, you can measure it to be a zero or one.
And it has no effect on that second photon.
But when they're entangled, measuring one of the photons tells you exactly what you're going to measure in the other one.
This is because, as I said, they are inherently dependent on each other when they're in this state.
When they're in a state of entanglement, it's a system of two photons.
It's not two individual photons.
So you can't measure one without affecting the other.
It's not like there's any communication going on between these two.
You can take them at an arbitrary distance and do this as well.
Opposite ends of the universe.
You can measure one and it will not send a message to the other one saying,
hey, they just measure me to be a zero.
Heads up.
They also don't collude ahead of time before you separate them and agree to a certain value.
It's spooky action at a distance, as Einstein said.
I don't know how it works.
I don't know the underlying meaning of this at all.
But it's very clear in the math.
So let's talk about that other quantum property, superposition.
This one's just as spooky.
I assure you.
And yet, it's nothing to really be afraid of.
So superposition, unlike entanglement, has great analogies to understand it sort of.
So one analogy is coin, a coin flipping or spinning on a table.
A coin, if it's laying there, we can say that it's either heads or tails based on which side is facing up.
But if it's spinning on a table, or if it's in the air and you're flipping it,
is it heads or is it tails?
Well, of course, it's neither one really.
With some probability alpha, it will end up being heads.
And with some probability, say beta, it will be tails.
Don't know that until after the fact, the outcome will be with probability one, heads or tails.
And not both.
But in the meantime, if a coin is spinning around on the table, it's in a position where it might be either one.
Now, maybe this is not even a fair coin.
Maybe the probability of heads is not one half.
And the probability of tails is not one half.
Maybe it's the probability is very high that it's one and very low that it's the other.
But it's some combination of those.
That's kind of the way quantum bits or qubits are when you're operating on them.
These particles can be put in a state of superposition.
Now, what does that mean?
Okay, here's the part where it gets a little strange.
One interpretation of the way this really works and what's really going on is from 1953 from a guy named Everett called the many worlds interpretation.
This holds that when I spin the coin or when I put a quantum bit into a state of superposition,
there's actually two universes created.
One in which I observe the qubit to be a zero and one in which I observe the qubit to be a one.
Yes, you heard me right.
One universe in which the observer sees a heads, one universe in which the observer sees tails.
Both existing simultaneously.
Now, when that state collapses, it's either not to be heads or tails, right?
So, what is really going on here?
Well, according to this interpretation, I can measure the qubit afterwards.
And what I've done is I've collapsed not the state of the qubit that was in superposition.
I've collapsed the state of me, the observer.
I've entangled myself with one of those universes.
That state of superposition still exists for a different independent observer that cannot see inside of the system
in which this has collapsed down to one universe.
I know, that's really strange stuff.
And you know, I have another great quote from Einstein about that.
He said, I like to think that the moon is still there, even when I'm not looking.
What did he mean by that?
He meant this strange idea about particles that Heisenberg championed, called the uncertainty principle.
Heisenberg said, you can't know the position and the momentum of a particle.
You can know one, but not the other.
So, does a particle exist at a fixed position in space at a given point in time?
Well, we like to think of particles that way, like they're a little billier ball, in a certain place at a point in time,
headed in a certain direction with a certain speed, just like the large objects that we see in our everyday life.
A car on the road that's driving down the road, at a certain point in time T, it's at a specific place going in a certain direction at a certain speed.
Particles don't act like that, though, unfortunately.
They don't exist at a fixed position in space at a given point in time, until and unless we observe them too, that's the weird part.
Heisenberg was onto that, and Einstein complained about that.
The moon is a very large object, not a particle, obviously, but you get the idea.
We really want to consider these things as acting like normal objects in our everyday lives, and they really don't.
So, a particle can be in a superposition of multiple states.
We can have a particle be in a combination of zero and one, and when we need to, when we're done doing our computations with it,
we will measure it, and by doing so, we will observe it to be a zero or a one.
We've caused that to happen through our act of observing it.
So, consider two qubits now.
They don't have to be entangled, like we talked about earlier, but two qubits in a state of superposition.
If there's one qubit, it can be in a superposition of one and zero.
That is, it exists as a linear combination of two possible states.
So, what about two qubits in a state of superposition?
Well, think about two coins spinning around on a flat surface.
What are the possible outcomes?
Could be both heads. Could be heads in a tail, a tail in a head, or two tails.
There's four possible states for the outcome for those two coins.
If it was three coins, there's eight possible states for the outcome.
So, you could say that when the two coins are spinning around,
they exist in some linear combination of those four possible states,
one of which will ultimately result when they deco here.
I make no apologies for throwing in yet another piece of jargon there.
Deco hearing is what actual qubits do.
The coins don't, the coins quit spinning at some point and fall down and become a heads or a tail.
Two qubits in a state of superposition represent some combination of those four possible states,
zero, zero, one, one, zero, and one, one.
So, they are some combination of all four of those.
Now, entanglement is a special case.
Entanglement is the case where the two qubits only represent a combination of zero, zero, and one, one.
This is what's different about quantum computing when you have entanglement from ordinary computing.
In ordinary computing, we've got two coins that are spinning.
They could be any one of four outcomes.
You can't spin the coins in such a way that they always come out to be either both heads or both tails.
I don't know how to do that, but it's easy to do with quantum bits or qubits.
We put them into a state of entanglement to do that.
So, there you have the two principal quantum effects that we're employing to do wonderful things that regular computers can't.
Entanglement and superposition.
And I hope you are impressed that it does not matter if you don't understand what's really going on here.
Does anyone?
But there's another point to say about superposition.
Now, with entanglement, we're able to do weird things that you can't do with regular computers.
Like, have two coins spinning that will always come out to be both heads or both tails.
That turns out to be really useful property in some unexpected ways.
But superposition, what that gives us is this incredible potential for power.
And the way I like to explain that is to consider first bits.
If I have eight bits, classical computer bits, each of which holds a one or a zero.
I can represent any one of two to the eighth different values or 256 values.
As unsigned integers, that means I can have zero to 255 in total.
They will represent one of those 256 values.
Now, when these bits are in a state of superposition, it's different.
Remember, when there was two quantum bits in a state of superposition,
they represent some combination of four states at the same time.
And you can do operations with them in that state.
And then when you're done computing, you measure the outcome.
So now let's scale that up from two quantum bits to eight.
So with eight qubits in a state of superposition,
we're now representing some linear combination of 256 states at once,
with only eight qubits.
Let's say we're trying to solve a problem with 256 possibilities.
Well, we can do operations against all those possibilities at once potentially.
Now, where are the implications for that?
Well, the smartphone that I've got in my hand has a chip in it with billions of transistors on it.
If we ever got anywhere near that scale with quantum computing,
the potential compute power would be staggering.
And to kind of quantify this, think about a system with 500 qubits or a thousand qubits.
So with 500 qubits, you can represent two to the power of 500 different states at once.
But just rough numbers, really rough numbers.
That's a one with 150 zeros after it.
How big is that number?
It is bigger than impossibly big to imagine how big that number is.
Put it this way.
All the particles in the visible universe, not even close to that big.
All the units of time since the big bang, not even close to that big,
if you're measuring femtoseconds.
So what that tells us is if we were to build a classical computer
that somehow was able to utilize every particle in the visible universe to store a bit,
150 or 1 in, and it could do that.
For every moment of time since the big bang, we still couldn't store all the possible states
that a simple quantum computer with 500 qubits would be able to do.
That is the unimaginable potential power of these things.
Now, how does nature accomplish that?
I haven't got a clue, and we really can't gain insight into the system
because what's happening is not available for us to observe in any way.
Any interaction with particles affects some change in those particles.
Any interference whatsoever, and let's face it,
there is no other way to observe anything without interfering with it.
It means that we will never be able to really pull back the curtain and see what's going on.
But we know there is enormous potential, and this is why you see so much excitement
and so much investment from governments and big companies into quantum computing.
They see the potential for the future.
Now, just to wrap this up, to paint the big picture,
there are people all around the world working on quantum processors,
on quantum algorithms and quantum compilers.
There are resources out there like programming frameworks in Python
that can compile down to different hardware platforms.
There are computing architectures available for anyone online for free.
That's right, online for free for anyone to use and run their little programs on.
For example, just one example, IBM Q Experience.
You can go online and run a little simulation, run a real program on a real quantum computer and get an outcome.
There are people working on quantum networking.
Eventually, we're going to have computers with quantum processors using quantum memory.
They're going to be a little different. They're going to be fault tolerant,
which they aren't currently. That's a huge area of research.
And they're going to work hand in hand with classical computers.
There's no doubt about that. The control systems are controlled by classical computers.
And don't forget the output we need to get needs to be deterministic.
These things are probabilistic in nature.
And we want definite reproducible answers that are clear cut ones and zeros.
So these systems will not exist independently.
But they will be networked and will have communication protocols and cryptography that is all based on taking advantage of these quantum effects.
The very first program you'll write when you start learning quantum computing is teleportation.
And this is a great one because you're able to transfer the value of a qubit without measuring it to destroy the state of superposition.
You can transfer it. Why is that a big deal? Because you can't copy a qubit.
That's the same underlying reason why error correction is so tricky in the quantum world.
It's very exciting times in the world of quantum computing because it's very early days.
We don't even know the technologies involved yet.
The hardware architectures will surely involve photonics.
For networking in particular, this looks like the clear winner.
For quantum processors, it seems like a pretty safe bet that superconducting qubit technology, which is kind of the leader at this point in time.
This is what companies like IBM and Rigetti and Google are using, will surely be at least one of the competing technologies for the quantum processors.
But who really knows, there are competitors for that. And it's not clear what mix of what technologies will even be the winners.
This is kind of like in the middle of the 20th century when people were looking to build computers with vacuum tubes because transistors were not at the stage they needed to be yet.
Who could have really predicted the semiconductor technology that would end up with me holding a smartphone that had a little chip in it with billions of transistors packed in there?
It's very hard to predict these things and there are competing technologies that are fascinating but very different from each other in most ways, very similar to each other in some ways.
And you really start to understand that when you look at the various levels from the hardware level, do the control systems all the way up through the stack with the programming environment being on the top and being compiled down and optimized along the way, all the way down to ultimately a set of pulses or signals.
These are physical systems after all involving photons or electrons or ions. There's very interesting stuff going on there too much to talk about now but whatever it is you're interested in and want to hear more about, comment about it and let me know.
And we might head in that direction in a future podcast.
Until next time, might be Mike, Hacker Public Radio.
You've been listening to Hacker Public Radio at HackerPublicRadio.org.
We are a community podcast network that releases shows every weekday Monday through Friday.
Today's show, like all our shows, was contributed by an HBR listener like yourself.
If you ever thought of recording a podcast and click on our contributing to find out how easy it really is.
Hacker Public Radio was founded by the digital dog pound and the Infonomicon Computer Club and is part of the binary revolution at binrev.com.
If you have comments on today's show, please email the host directly, leave a comment on the website or record a follow-up episode yourself.
Unless otherwise status, today's show is released on the creative comments, attribution, share a light, 3.0 license.
