About Quantum Computing

[RoGeorge]

Would be interesting to know what are the today beliefs and expectations about this new area.   

[BravoV]

Probably just for me, always stick to "The proof of the pudding is in the eating" .. and until today, no simple explanation for average Joe like me exist, on why I need to use it. 

PS :
Just assume I have an average intelligent level, starting to grip on Einstein's theory of special relativity  , and so filthy rich that is itching to invest on the computing field.

[RoGeorge]

Indeed, it's quite a salad of physics (quantum physics), math (linear algebra with complex matrices) and computer science (algorithms, big O, etc.), all sprinkled with news hype and confusing words like "teleportation", "oracle", "spooky action" and that famous "zombie cat"  , with none of these terms meaning what the quoted words suggest.

[BravoV]

Indeed, it's quite a salad of physics (quantum physics), math (linear algebra with complex matrices) and computer science (algorithms, big O, etc.), all sprinkled with news hype and confusing words like "teleportation", "oracle", "spooky action" and that famous "zombie cat"  , with none of these terms meaning what the quoted words suggest.

Yep, a great example, on how the US President explained to "avg Joe" the reason for sending human to the moon.

Quote :
"In his speech, Kennedy characterized space as a new frontier, invoking the pioneer spirit that dominated American folklore. He infused the speech with a sense of urgency and destiny, and emphasized the freedom enjoyed by Americans to choose their destiny rather than have it chosen for them."

Great speech imo, plain simple yet so powerful. 

Wish one day, at least "one" of those quantum scientists, is smart enough to come with words that on the par like that above, cause I don't see there is a need to bombard confuse the lay people, with space science tech jargons like the rocket science, which I believe it will be too overwhelming. 

[RoGeorge]

That was a very powerful speech.  However, it is very unlikely a scientist will ever say such words about quantum computers.  First, because that was a motivational speech delivered by a politician, then, because there is no final goal and no deadline defined for quantum technologies.

Anyway, about the confusion when reading about quantum "whatever", I felt myself exactly the same frustration.  After all, nobody asks about the most abstract formalism to be detailed in a magazine, but at least a rough description of how things work would be nice.  Unfortunately, the same generic (and IMHO fundamentally wrong) fairy tales are repeated over and over.

Here's the two cents of my current understanding:

1. Superposition, AKA the Schrödinger's-cat being dead-and-alive at the same time.

This is probably the most damaging ideea repeated over and over.  It is not true, and it shouldn't be used at all.  The so called "Schrödinger's cat" tale adds no value in understanding the concept of superposition.  It's a distraction for everybody (funny cats, metaphysical thoughts about life and death, etc.)  Simply said, this idea is the maximum damage one can come up with when talking about superposition.  Let's forget about the poor zombie cat.

OK, so what it is "superposition"?

Superposition is NOT true and false at the same time.  It is EITHER true or false.  Then, why not just saying so?  Because, in fact it is not about a discrete value, like true/false, or 0Volts/+5Volts in a digital computer.  It is, in fact, a continuous value.  For example it can be 0.5V, or 4.7V, or maybe 2.5V, or any other value between 0 and 5 Volts.

Let's say you have a 0 to 5V adjustable voltage source.  You set the voltage to 3.8V but I don't know that.  The problem is I don't have a voltmeter to measure the exact voltage.  All I have is a logic probe (or a comparator) with a LED.   I will never know you set it to 3.8V.  Since it was set at a voltage higher than 2.5V, my LED will shine, and I'll say it's a logic 1, or a true.

That is why I will say "The voltage was in a superposition (for me) until I measured it with my LED.  Now that I've measured it, I know it's value was "LED was turned ON"". 
- Note the "voltage superposition" is just another way of saying "somewhere between 0 and 5 Volts".
- Note that I will never know the real value of 3.8V, because my LED is not capable of displaying different light intensity, my LED can only shine on or off.  The real value, 3.8V, it's called "the probability of the event", but we won't go into details about the probabilities, not for now.

[BravoV]

That was a very powerful speech.  However, it is very unlikely a scientist will ever say such words about quantum computers.  First, because that was a motivational speech delivered by a politician, then, because there is no final goal and no deadline defined for quantum technologies.

LOL ... sorry, yeah, I exaggerated, and don't expect those so called smart genius quantum computing scientists to be able to deliver that kind of quality "communication" like Kennedy did.

What I really want to hear is the impact to humanity, on this subject.

My grandma does understand and appreciate the thing called computer + internet, that can made her having a clear & crispy video call with her grand kids and seeing around the place they live, even across the globe. Without having to suffer bombarded by jargons like bits per second, video stream compression, SSD, network routing , 5G network mesh etc. 

So this quantum computing, is it just another new type of computer ? Like IOS vs Android thingy ? If that is the case, then it still computer right ? So what so big deal about it ? Say compared a PC era, and then suddenly sort of morphed into "big deal" with handheld smart phone that transformed and improved significantly on humanity for communicating each other, this is really simple yet powerful example that any average Joe can understand.

Btw, subject to my grandma, I'm pretty confident that I can craft a suitable explanation to her regarding the ITER, International Thermonuclear Experimental Reactor  , and trust me, no jargons like magnetic plasma confinement, tokamak and etc are needed at all. 

[RandallMcRee]

So much nonsense in this thread!

Quantum computing is real. One algorithm that it enables, if a successful quantum computer can be built, allows cracking of previously unbreakable cryptographic codes, i.e. most of the ones we use today. There are others, but this is the one that folks (physicists, computer scientists) agree is real and has a real impact.

https://en.wikipedia.org/wiki/Quantum_computing#Cryptography

Btw, superposition is real, too, and is not what is described in this thread.

[BravoV]

So much nonsense in this thread!

Quantum computing is real. One algorithm that it enables, if a successful quantum computer can be built, allows cracking of previously unbreakable cryptographic codes, i.e. most of the ones we use today. There are others, but this is the one that folks (physicists, computer scientists) agree is real and has a real impact.

https://en.wikipedia.org/wiki/Quantum_computing#Cryptography

Btw, superposition is real, too, and is not what is described in this thread.

So its nothing more than, say like the dark matter right ?

PS : About the link you pointed above, I stopped reading when I bumped on this words "is believed".

[emece67]

.

[BravoV]

PS : About the link you pointed above, I stopped reading when I bumped on this words "is believed".

It says: "[...] is believed to be computationally infeasible with an ordinary computer [...]", so the believings are not related to quantum computers but ordinary ones.

Ok, I loose,  now can you help to explain it to your grandma  ?

[Bud]

Yep, a great example, on how the US President explained to "avg Joe" the reason for sending human to the moon.

Quote :
"In his speech, Kennedy characterized space as a new frontier, invoking the pioneer spirit that dominated American folklore. He infused the speech with a sense of urgency and destiny, and emphasized the freedom enjoyed by Americans to choose their destiny rather than have it chosen for them."

What is so great in it? From today's view it is a blah-blah BS.

[Bud]

Everyone is saying the primary use of quantum computer is to hack encryption. What IBM is saying at this time  it is simulation of processes occurring in the Nature.

[edy]

Ok, I loose,  now can you help to explain it to your grandma  ?

I refer you to a "Gentle Introduction" to Quantum Computing.....

http://mmrc.amss.cas.cn/tlb/201702/W020170224608150244118.pdf


      

And then after you read the "Gentle" introduction, you can ask grandma to continue reading the regular introduction to Quantum Computing:

http://mmrc.amss.cas.cn/tlb/201702/W020170224608149125645.pdf


    

And finally to top it off, this wonderful "BASIC CONCEPTS" to just give us the simplest basic understanding...

http://www-reynal.ensea.fr/docs/iq/PrinciplesOfQuantumComputation1.pdf

Once we've all read these 3 basic gentle intros I invite us back to continue discussing the topic.     

[RoGeorge]

About breaking encryption, not so fast.  There are many types of encryption, some of them are unbreakable no matter how powerful or how fast is the computer, quantum or not.

An example of such an unbreakable scheme is a simple XOR.  If we both met and take each a copy of the same random string of bits (longer than the message), AKA our secret encryption key, then we can later send messages by simply XOR-ing bit by bit the message and the key.  If an ataker intercept the message and try all the possible keys one by one (a brute force attack), then the intercepted message will turn into ANY possible messages, including the one I sent.  The difficulty here for the attacker is that from all the possible combination of letters, some are gibberish and some are making sense, but the attacker will never know from all those that makes sense, which ones are fake and which one is the real message I just sent.

In other words, it will be like arresting all the people from the entire planet.  Now, you have them all, except you can not tell which one is the guilty one.   

Some other encryption schemes, like RSA, are vulnerable, but even so, that doesn't mean it will be the end of encryption.  We will just move to some other encryption schemes that are mathematically proved to be unbreakable.

[SiliconWizard]

But can it be used for the next generation of autonomous vehicles?
 

[AlfBaz]

intercept the message

There will be no need for encryption, messages sent using quantum entanglement cannot be intercepted 

[RoGeorge]

That was about the impossibility of breaking some particular types of encryption, even if unlimited computing power is available.  It was about the common misconception that quantum computers brake ANY encryption.

An example of unbreakable XOR based encryption is called "One Time Pad":
https://en.wikipedia.org/wiki/One-time_pad

If the message can be sniffed or not, that's a different story.

[StillTrying]

if a successful quantum computer can be built,

Surely a quantum computer can and can't be built at the same time.

https://en.wikipedia.org/wiki/Quantum_entanglement  is my favorite.

[RoGeorge]

Quantum computers can be built, and they do exist.  They are still in their infancy, but there is no doubt about their existence.

One of such a quantum computer is IBM Q, which is freely available online to anybody who have the time to play with it.  One can run quantum algorithms either in simulation, or for real, on the hardware of a quantum computer:
https://www.ibm.com/quantum-computing/technology/experience

[ggchab]

Superposition is NOT true and false at the same time.  It is EITHER true or false.  Then, why not just saying so?  Because, in fact it is not about a discrete value, like true/false, or 0Volts/+5Volts in a digital computer.  It is, in fact, a continuous value.  For example it can be 0.5V, or 4.7V, or maybe 2.5V, or any other value between 0 and 5 Volts.

I understood the state is neither true nor false until we "look" at it. Then, we "force" the nature to reveal something and this will either be false or true.
That's fascinating but the theory is far beyond my understanding. I even read that nobody really understands what's behind the mathematics of quantum physics! Even more fascinating ! We don't really know what's happening. We have mathematical models that fit the observations, make predictions but they are models only...

[SiliconWizard]

On some level, quantum physics is a bit like burying one's head in the sand. If you can't see your observer, then it can't really see you either. Right?

That was the quantum moment of Pr. Proton.

[Marco]

This is based on absolutely nothing, but I have the suspicion that a lot of funding for electronic quantum computing is simply a distraction to keep optical quantum computing as far away from public research as possible.

[xrunner]

I understood the state is neither true nor false until we "look" at it. Then, we "force" the nature to reveal something and this will either be false or true.
That's fascinating but the theory is far beyond my understanding. I even read that nobody really understands what's behind the mathematics of quantum physics! Even more fascinating ! We don't really know what's happening. We have mathematical models that fit the observations, make predictions but they are models only...

I read somewhere that the Great Thinkers out there are hypothesizing that we're all in a simulation. The quantum stuff is the base "level" of observation that the simulation allows, because it has to be ready to portray whatever we end up looking at or choosing ... or something like that hell I don't understand it either. 

[RoGeorge]

Superposition is NOT true and false at the same time.  It is EITHER true or false.  Then, why not just saying so?  Because, in fact it is not about a discrete value, like true/false, or 0Volts/+5Volts in a digital computer.  It is, in fact, a continuous value.  For example it can be 0.5V, or 4.7V, or maybe 2.5V, or any other value between 0 and 5 Volts.

I understood the state is neither true nor false until we "look" at it. Then, we "force" the nature to reveal something and this will either be false or true.

That's fascinating but the theory is far beyond my understanding. I even read that nobody really understands what's behind the mathematics of quantum physics! Even more fascinating ! We don't really know what's happening. We have mathematical models that fit the observations, make predictions but they are models only...

That is exactly how I think it is.

In fact, all the quantum computing would be much easier to understand if we think about it like it would be an analogical computer, in the same way we use to have "computers" before the digital era.  Back then, to do for example an addition of 2 + 3, you were just putting together a 2 Volt and a 3 Volt voltages at the input of an amplifier (through a resistor each), and you get the response of a 5V at output, and that was the result.  No bits, just a contiguous analog voltage.

In fact this is how quantum computers are really working right now.  The only difference is that, for the quantum computers, we can't measure the analogic value of a qubit, and all we can say when we "measure" or "look" at a qubit is that the qubit is "less than half" (a logic 0) or "more than half" (a logic 1).

Qubits are so small and "fragile" that we completely "smash" them into a "less than half"/"more than half" state when we "measure" them.

The implication of this idea is that it is possible for a clasical analogical computer to do any calculations a quantum computer could do.  No need for cryogenic ions or other exotic quantum objects.

Another implication of the idea that "quantum computing" is nothing but "analog computing" with an extra step (by extra step I mean the measurement of the qubit) would be that quantum computing will probably never scale.  We already have had analogic computers in the past, but we are not using them any more because they do not scale well in complexity.  The scaling up is the main reason why digital computers are now everywhere.

The last option in this poll was "Quantum computers are not superior at all, quite contrary, they come with extra technological difficulties" exactly for this reason.  Quantum computers doesn't show any advantage versus a clasic analogic computer, but the quantum ones are very hard to handle and much more sensitive to noises and errors.

Those in computer science will probably argue about the big O number of steps, but I noticed the big O was calculated in an unfair way, thus making quantum algorithms to appear to be exponentially faster than other "clasical computing algorithms".  I should probably write a paper about the unfair calculation of the big O, but for now I would rather like to experiment and take the idea further.

[Jookia]

Mathematically almost all encryption is crackable by a computer, quantum or not. There's algorithms that do it in less 'steps' on quantum computers, but that doesn't really matter if a quantum computer can't perform those steps efficiently enough.