what is a "quantum computer" and does this have anything to do with keeping electronic elements extremely cold

no, not at all. but i can see where you’re coming from with that idea

quantum computers are numerical engines that share a lot of similarities with ‘computers’. they are tasked with performing complex algorithmic calculations just as a normal computer is. they begin to differ in the fundamental components and concepts used to perform such calculations

normal computers rely on binary encoding of data translating well to transistors, the fundamental building block of digital machines. a transistor is like a switch, either being on or off (’1′ or ‘0′). quantum computers rely on quibits, or tiny transistor-like components that exhibit quantum phenomena in a drastic enough fashion to be interpreted and relied upon during operation. what do i mean by this?

disclaimer: i’m not a physicist and don’t purport to understand quantum physics beyond an enthusiast level. quantum physics is difficult to understand conceptually and even harder to quantify

‘quantum phenomena’ refers to specific effects of quantum physics exhibited by very small, high energy particles. since everything is made up of very small particles, everything exhibits this phenomena to some degree. we can make very small assemblies that exhibit quantum phenomena more readily and drastically and dependably relative to their size – quibits

digressing for a second

the fundamental principle behind quantum mechanics is pretty straightforward. the study of physics relies on building mathematical models and formulas to describe how things in the real world react according to measurable properties. you then build experiments to empirically determine if these models and such are correct. that involves putting them in some controlled environment and measuring them. if the measurements result in figures that follow your model, your theory gains credibility

this worked for newton “apple falling from a tree” shit. it stopped working once we started to apply that methodology to things like electrons and photons. why?

because when you start dealing with media that small and high-energy, you cannot reliably measure them without drastically changing their state. you can tie a string to an apple and measure how quickly that string unwinds from a roll to track the velocity/acceleration of the falling apple. the resistance the thin string’s mass exerts on the falling apple is very small and doesn’t drastically change the results of your experiment (it can also be accounted for). you can’t measure any property of electrons or photons or other small, high-energy particles without severely changing their state (velocity, energy, etc). your measurements become useless – you need to know these properties as they appear organically and not after the inflicted effects of measurement. you can’t work backwards from your results either, like in the previous case where we subtracted the effects from the tiny mass of the string inflicted on the falling apple. this is because particles on this scale also seemingly tend to react in truly random, unpredictable ways, and that is the side of quantum physics that starts to becoming insanely complicated

anyway

since we can’t get direct results anymore, we had to change the fundamental model of how we conducted physics at this scale. we factor in the uncertainty of the unknowable details of experiments, and we go from our answers being flat numbers to infinite sums of probabilities of certain things being the answer

there’s a simple thought experiment that explains what i’m about to talk about, but it’s pop-science silliness that involves killing cats, which won’t go over well on the blue website, so let me give you a better idea:

when we sit down and try to incorporate these “directly unknowable” variables into our model, we have to describe them in terms of quantum superstates. these superstates arise from entities existing in quantum entanglement which is a fancy way of saying “two possible states abstracted into two discrete entities that devolve into a singular state upon measurement”. let’s stop here

(end regression)

quibits, like i said before, are the analogue to transistors in a quantum computer. they can be described as two states that can undergo entanglement from controlled stimuli. the two states, when not entangled, are ‘1′ and ‘0′ – just like a normal computer

however

when they conditionally undergo entanglement, they enter a superstate between ‘1′ and ‘0′. this is hard to imagine. they are both ‘1′ and ‘0′, while also being neither ‘1′ or ‘0′, simultaneously

why this could possibly be a benefit to a computational engine is beyond my abilities of enunciating. but it is hugely beneficial towards solving some specific problems within timeframes exponentially shorter than they would be on a normal computer

it’s important to note quantum computers are not anything at all like ternary computers, which are computers whose fundamental component is tri-state (0, 1, 2). i had answered an ask about ternary computers a while ago, but i’m afraid it’s lost forever due to this fucking sites lack of a proper search function

anyway, these specific problems that quantum computers are theoretically better-able to solve are few and far between. quantum computers aren’t anything near what people think they are: just normal computers that run incredibly fast. they are not general purpose computational engines like the processors in the computer in front of you. they are purpose-built to solve exactly one of these specific problems

now

the existence of quantum computers today is complicated. scientists have successfully produced quibits, even ones that react dependably enough to be used in a quantum computer. i know this because of published results circulated in academia. if you had to ask me, i would guess that one or more legitimate quantum computers exist on this earth, and that they certainly were manufactured by the united state’s national security agency. the USA, for obvious reasons, does not disclose their defense secrets which is what makes this complicated

why would the NSA want a quantum computer? the specific problems i mentioned earlier, the ones best suited for quantum computers, are ones that involve cracking encryption within timeframes that would be totally unfeasible on normal machines. the process of cracking encryption, on a normal computer relies on constantly encrypting sets of random data with the same algorithm used to encrypt the data you’re trying to crack. when your output equals the target encrypted data, you know that your input equals the target unecnrypted data, which is the end product you’re looking for. this is incredibly inefficient and in most cases would take every computer ever manufactured running from the beginning of the universe until its eventual heat death trying to crack one piece of data, with maybe a .001% chance of actually getting it. this is why encryption works

however, it assumes you can’t analyze the encrypted data and mathematically “work backwards” from it to get the initial target data or key used to encrypt it. this is getting into an entire different topic, if you want to know more about this send another ask

anyway, those barriers to reverse-engineering fall apart in the context of a quantum computer. for example, the critical principle used in one-way hashing algorithms that prevents the simple decryption of them by “working backwards” is the abel-ruffini theorm. it, perhaps, no longer holds true when you have a machine capable of existing in quantum states, meaning these hashes would be easier to break

finally, the whole “keeping computers very cold thing”. this one i can actually explain beyond and armchair physicist’s level

electricity flows through conductors. “electricity” is a way of describing moving electromagnetic charge in the form of drifting electrons. “conductors” are elements that facilitate the drifting of these electrons in a way that doesn’t impede them as much as resistors. the line between the two is completely arbitrary: compounds or elements with a resistance of less than one ohm are considered conductors, those with 1 or more ohms of resistance per unit length are considered resistors

the patch electrons take when moving through a conductor or a resistor can be described as a waveform. they move in a wave pattern, smoothly alternating between going up and down while preceding laterally in a direction that is perpendicular to ‘up’ and ‘down’:

image

when electrons drift up and down (blue/green arrows) they lose energy in the form of heat and imparted momentum. things with very high resistance won’t carry a charge well at all, they’ll just heat up when you pump electricity in them. conductors, alternatively, will carry it well with minimal up/down movement

now

measuring something’s conductivity/resistance is involves many more aspects than just what it is atomically composed of. temperature plays a huge role: things that are much hotter display much higher electrical resistance than things that are colder

when you take obnoxiously conductive compounds, and reduce their temperatures to obnoxiously low temperatures (near absolute zero using liquid helium-2), they start to exhibit a fantastically interesting phenomenon: superconductivity. their resistance falls to zero. not arbitrarily close to zero, not virtually zero, but zero. electrons drift like this:

image

this enormously reduces the complexity involved in modeling them at very small scales, and we know that at very small scales quantum effects begin to arise in such a way they become relevant. this lack of complexity previously barred us from modeling them at this scale, and by lifting that barrier we get control and insight of a system we did not previously have. this is probably important

here is where i think the link between extremely cold circuity and quantum computers comes into play w/r/t your question, as superconductors are probably a part of how one comes to build a functional quantum computer. superconductors being a necessary component of them is probably why quantum computers will never exist outside of very specialized and well-funded scientific or defense departments

bonus: liquid helium-3 is a bitch to keep around, and we’re also very quickly sucking all the helium out of the earth. once we do, that will be it – no more helium forever. there’s no way to reclaim it as it quickly floats out of our atmosphere. there’s no way to reasonably synthesize it either: it’s an element, specifically a noble gas that doesn’t naturally bond with any other element to form a compound that could stick around in our atmosphere. the only way it comes about on our earth in a non-negligible way is through the alpha decay of slightly heavier elements: something that happens inside the earth over trillions of years, conceptually similar to oil. liquid helium is a totally non-renewable resource and an absolutely necessary component of MRI machines, particle accelerators, and many other important technologies. i urge you to educate yourself and get involved with helium conservation efforts, as pretty soon we will run out of the second most abundant element in the universe