What is a quantum computer?

[notsheigetz]

I'm interested to know because there is a Lockheed Martin plant right across the street from me and because Google just bought one of their quantum computers (I've resisted applying for a job with them because I've always figured they were mostly about blowing people to kingdom come which I would rather not be involved in).

I'm a software engineer (aka computer programmer) who flunked high school physics but I've gotten interested in Quantum physics/mechanics of late. My knowledge is constrained to what I read in popular science books.

In my personal computing experience everything can be distilled down to basic equations wherein one can rely on the fact that there are only two states of matter - either true or false, aka binary. From my understanding of quantum mechanics, this doesn't fly any more. At the quantum level we have to deal with things like the "Heisenberg Uncertainty Principle". Basically, things are neither true nor false any more. It all depends, mostly on whether you are looking at it or not.

(And in my reading on Quantum mechanics I learned that Einstein actually received the Nobel prize for his work in this area and not the theory of relativity as most people would assume. He later disavowed some of it as nonsense that would eventually be discarded when the truth became known but as I understand it the opposite happened in his lifetime.)

So, if there any geniuses in physics on the board (and I think there might be), can you explain to a layman like me in simple language how there can be such a thing as a quantum computer?

[dualstow]

I think you might have Heisenberg's Uncertainty Principle mixed up with the Observer Effect, but I'm not sure.
I definitely cannot answer the question "what is a quantum computer" even though I see headlines about them every week.

Even this "simple English" page is not so simple.
https://simple.wikipedia.org/wiki/Quantum_computer

[Ad Orientem]

[RuralEngineer]

It's been a while, but from what I can remember it goes something like this (forgive me if I lead you astray, I am not an expert on Quantum Physics):

A normal computer performs computations using transistors as switches to either be on or off, a 0 or a 1.  This is binary.  Most people know this.  A Quantum Computer is doing the same thing but instead of using transistors, it's using the spin state of particles (up or down as I recall).  I believe at one point they were also talking about using the energy state of valence electrons as well, which would actually be more than just a 0 or 1, but that may have been abandoned.  In any case, if you're looking at the spin state of an electron on an atom for example, and it can either be up or down, that's just like a transistor and you're still using what is essentially binary.  However, because you're doing it at the subatomic level all the things that plague us right now like heat and the spacing of transistors go away.  You can also have multiple electrons per atom depending on the material (no idea what kind of materials they're looking at, but it's likely superconductors so N2 or He2 cooled), so potentially you could have lots of "transistors" per atom.

[Libertarian666]

It's been a while, but from what I can remember it goes something like this (forgive me if I lead you astray, I am not an expert on Quantum Physics):

A normal computer performs computations using transistors as switches to either be on or off, a 0 or a 1.  This is binary.  Most people know this.  A Quantum Computer is doing the same thing but instead of using transistors, it's using the spin state of particles (up or down as I recall).  I believe at one point they were also talking about using the energy state of valence electrons as well, which would actually be more than just a 0 or 1, but that may have been abandoned.  In any case, if you're looking at the spin state of an electron on an atom for example, and it can either be up or down, that's just like a transistor and you're still using what is essentially binary.  However, because you're doing it at the subatomic level all the things that plague us right now like heat and the spacing of transistors go away.  You can also have multiple electrons per atom depending on the material (no idea what kind of materials they're looking at, but it's likely superconductors so N2 or He2 cooled), so potentially you could have lots of "transistors" per atom.

No, that's just a very small conventional computer switch. Quantum computing uses the superposition of quantum states to calculate many different results simultaneously.

[dualstow]

Basically, things are neither true nor false any more. It all depends,

I got an insight into this during my first long-term relationship with a woman who, in thirteen years, despite being exceedingly bright never answered a direct question with a yes or a no. Maybe a quantum computer is like her brain.

[doodle]

Basically, things are neither true nor false any more. It all depends,

I got an insight into this during my first long-term relationship with a woman who, in thirteen years, despite being exceedingly bright never answered a direct question with a yes or a no. Maybe a quantum computer is like her brain.

She did that because she was exceedingly bright. "Yes" or "No" implies surety and as Bertrand Russell says "The fundamental cause of trouble in the world is that the stupid are cocksure while the intelligent are full of doubt."

[dualstow]

Well guys, I don't think Bertrand Russell would have applied his assertions to such questions as "Is your tummy feeling better" or "Is there still chili in the fridge."

She did that because she was exceedingly bright. "Yes" or "No" implies surety and as Bertrand Russell says "The fundamental cause of trouble in the world is that the stupid are cocksure while the intelligent are full of doubt."

Basically, things are neither true nor false any more. It all depends,

I got an insight into this during my first long-term relationship with a woman who, in thirteen years, despite being exceedingly bright never answered a direct question with a yes or a no. Maybe a quantum computer is like her brain.

She did that because she was exceedingly bright. "Yes" or "No" implies surety and as Bertrand Russell says "The fundamental cause of trouble in the world is that the stupid are cocksure while the intelligent are full of doubt."

seems like Bertrand was awfully sure of that
try looking up E prime some time if you haven't already, i think you might find it interesting
it is "can be" a mind altering experiment to try to speak in nothing but E prime for a period of time...

[doodle]

Well guys, I don't think Bertrand Russell would have applied his assertions to such questions as "Is your tummy feeling better" or "Is there still chili in the fridge."

She did that because she was exceedingly bright. "Yes" or "No" implies surety and as Bertrand Russell says "The fundamental cause of trouble in the world is that the stupid are cocksure while the intelligent are full of doubt."

not sure what Burt would say but in E prime the answer would be something like " my tummy seems to me to be feeling better (worse) at this point in time" "or there was something that appeared to be chilly the last time i looked"

From my understanding E-prime doesn't allow any form of the verb "be". Once you get used to this and figure out some appropriate expressions to work around it, it should be pretty easy. 

Is your tummy feeling better? - (Does your tummy feel better?)
My tummy seems to me to be feeling better (worse) at this point in time" - (My tummy feels better / worse at this moment)
Is there still chili in the fridge? - (Does any chili remain in the fridge?)
There was something that appeared to be chili the last time i looked - (The last time I looked in the fridge I saw chili.)

its been a while but that is the basic idea of it, eliminating "is" or "be" from ones vocabulary, i don't recall the exact rules for the exercise regarding the qualified use of "be" like my examples....... my impression was they are allowed..

it is more difficult to manage in daily life than you might expect... i think the suggestion was snapping your wrist with a rubber band every time you slip to see how often they are used and reinforce your effort to catch it and speak E prime

[notsheigetz]

I got an insight into this during my first long-term relationship with a woman who, in thirteen years, despite being exceedingly bright never answered a direct question with a yes or a no. Maybe a quantum computer is like her brain.

This was really an experiment to see how long it takes for a subject to go off-topic but I give you the award for best answer any way.

[l82start]

a quantum computer is much like a wife, its thinking is based on some sub atomic algorithm of irrational yes, no, maybe, equations that men are unlikely to ever fathom, and doomed to get the wrong answer for, every time the probability field is collapsed....