Justin Trudeau explains the basics of quantum computing to reporters

/r/iamverysmart

There's just no impressing you, eh?

Do you honestly believe that the majority of people (hell, even 10% of people) could explain it to even the level he did? It's still a layman's level -- his response is clearly over-simplified and I doubt he could show the math behind any of it -- but it's far and above what the average person could tell you about the subject.

Watching dozens of videos of Americans answering geography questions would lead me to disagree with you on what the average person knows about quantum physics.

The Canadian media is highly supportive of Trudeau at the moment and, with the exception of more reputable periodicals like the Globe and Mail and the National Post, are taking every opportunity to gush.

That said, Trudeau has shown a significant capacity to leverage those around him to display competencies he wouldn't have on his own.

> I see no evidence that his knowledge is any better than a layman's

Really? I got the impression that he didn't really get the significance of Q-bits and just thought of it as 'stores more stuff than a digital-bit; MORE GB!!!'.

At the same time, I'd be surprised if a man-on-the-street interview would give anywhere near as good of an answer.

> It's pretty sad that people are surprised or impressed when a politician has a layman's understanding of something in science.

Sad yes, but probably a mentality brought on by the number of U.S. politicians who activity don't believe and don't understand many things in science (great answer from Carl Sagen on Charlie Rose on this: https://youtu.be/U8HEwO-2L4w?t=56).

It might just be a reflection on North American politics, but I think it is impressive when a politician is willing to educate themselves about the basics of any technical subject.

When you have half of the American candidates denying climate-change or evolution, you get excited when you see a political leader who evidently has taken the time to have a basic understanding of new and upcoming fields of study.

He went around the perimeter institute building in Waterloo Ontario in Canada and spent some time learning the basics and trying to understand the work that they do there. He did understand the basic ideas that he was saying, it wasn't just a script and he was active and engaged learning throughout the day. Obviously he won't understand very much detail about it, but he doesn't need to. He is a prime minister, not working in this complex field of study. His goal has been trying to understand these more modern technologies so that he can better make decisions for the future. It is important for policy makers to understand the things they are making decisions about.

Agree 'Normal computers work, either there’s power going through a wire or not. It’s 1 or a 0.'

I believe power does not go through the wire, it is current or charges, and usually voltage is used to signal states. We can have wires depending how you define a computer, but in most cases it just feels wrong.

Well, he did spend two years studying engineering at a decent school, so it's reasonable to expect him to have a higher aptitude for these things.

Also, you're way overestimating how much a layman knows about computing, quantum or otherwise.

It was a coherent summary of a complex subject, delivered clearly, with just enough information to support the point of his message without getting bogged down in details. This takes skill; popular science writers make their livings and sometimes even become famous based on their ability to create this kind of summary.

Whether or not Trudeau's knowledge of the topic goes any deeper than what he's said here, he's demonstrated that he either cares enough about the subject to have consulted with people who understand it and learned how to repeat their explanations without falling off the rails, unlike good ol' Senator Ted "Series of Tubes" Stevens for example, or that he cares about the subject enough to have learned enough about it that he can articulate an opinion in a clear and accessible way. Either way, what's impressive is not that he is repeating information which is true, but that he cares enough about quantum computing to get it right.

> Do you multiple a qubit of infinite values against a quibit of infinite values and have all possible results?

The accurate answer would be "no", or at least "thinking that way will lead you to believe that they're more powerful than they are".

In particular, quantum computers won't allow you to solve NP-hard problems in less than exponential time, not unless there's something we're missing in the math.

That said? Since I don't have the chance to describe it better right now, you can start off by thinking "sorta, yes".

Google 'quantum complexity classes'.

One qubit could hold 0 and1 simultaneously and perform some operations/calculations on it simultaneously.

Two (entangled) qubits could hold 00, 01, 10, 11 simultaneously and perform calculations on these four values simultaneouslty.

...

100 (entangled) qubits could hold 2^100 distinct values simultaneously and perform calculations on them simultaneously.

That's the basic idea. The problem is keeping entangled state that's becomes harder and harder as number of entangled qubits grows.

Also there are limitations in extracting of calculations results from system of qubits, so not all algorithms can be speed up on quantum computers (but e.g. integer factorization can).

I'm no expert and might be horrible wrong on the math, but I imagine it like this:

2 bit => 2 ^ 2 => 1 of 4 possible state

2 qbit => 4 of 4 possible states. That's 4 times the information (although extraction of the information is limited)

With bigger numbers:

10bit => 1 of 1024 possible states

10qbit => 1024 of 1024 possible states (1024 times as much)

I was under the impression that the benefit of quantum computing was the ability to come to the "correct" answer for certain kinds of computationally complex problems instantaneously without having to actually "compute" them. So for example you'd spend a great deal of time up front engineering a way to present a problem to a quantum computer and when you execute said program it gives you the result that very moment without actually having to perform any traditional "operations".

So for example, let's say you wanted to figure out if some enormous number is prime. If you get your program right you could feed it to a quantum computer and all possible states of prime/non-prime would be measured at once resulting in the answer (state) being available the moment you "observe" it.

From this perspective quantum computing can be nearly infinitely faster than traditional computers while at the same time being mostly useless for every-day tasks such as surfing the web.

Note: This explanation is FAR from precise and is only trying to give an intuition

The key point is that qubits aren't limited to finite "multiple values", they can express an uncountable number of values. The best "short" answer is that a qubit can exist in a superposition (QM Term) of states. LOOSELY put it can have a probability of being a 0 and a probability of being 1 (with both probabilities adding to 1). This ability to encode information as the probability is the key to quantum computing.

When you measure (QM Term) the qubit, it takes on either the value 0 or 1 according to the probabilities you set it up with. This is computationally useful because with clever constructions you can make these probabilities meaningful.

For example Grover's Algorithm allows you to search an unsorted database for a particular item in O(sqrt(N)) time rather than the classical best O(N). The algorithm is successful with very high probability, note that because it uses the probabilistic nature of qubits, it itself can only be probabilistically correct, it just so happens you can make the probability of error very low (in theory lower than the chance your classical computer has a bit flip or similar)

The unfortunate restriction on QC is that you need enough qubits to encode your problem, if you can't hold the database in your "qubit memory" then you can't perform algorithm. In practice, building systems of qubits is extremely difficult and the current record is about 1000 as of 2015 I believe.

I couldn't recommend enough Michael Nielsen's on quantum computation. He has also written many articles:

http://michaelnielsen.org/blog/quantum-computing-for-the-det...

I'll try to answer this by presenting two types of computations a quantum computer is good at.

1) Quantum Simulation. So in a quantum system, your state can be in a superposition of states ("because waves"). There is a lot of information that resides in the way this system is in superposition and it determines how the system will interfere and evolve (amplification or destruction of certain states). Mathematically, it means you need to keep track of the complex amplitude of each of the 2^n states of a n-qubits system. On a classical computer, this means 2^n complex numbers are necessary to represent the quantum state.

However, on a quantum computer, you only need n-qubits to represent the quantum state, because qubits can be in superposition the same way any quantum state in nature can be. You can now do careful operations on your n-qubits state and simulate any quantum mechanical phenomena. It is therefore way easier to simulate quantum mechanics on a quantum computer than on a classical computer. This could be useful in many areas, like chemistry to simulate protein-folding.

2) Factorization (Shor's algorithm). It is possible to engineer a quantum state that is the superposition of all possible inputs. Then, it is also possible to carefully create interference so that non-solution of the factorization problems get lower amplitude, while solutions get bigger amplitude. At some points you can measure the state and collapse it in one of the state. Since the amplitude of the solutions is big compared to the amplitude of non-solutions, you get the solution with significant probability. You can then verify it using any classical computer because multiplying two numbers is easy. This algorithm breaks most of today public key cryptography used on the internet.

There are some great explanation here, but I wanted to add an article that gave me some insight about the subject: http://arstechnica.com/science/2010/01/a-tale-of-two-qubits-...

Canada should be congratulated for selecting a PM who atleast takes the trouble to educate himself before spouting an opinion.

Here in the US, we elect politicians who actively deny science and are proud of their lack of knowledge.

Isn't getting funding for science actually politics and not science? Using the funding is science, but getting the funding is politics, no?