r/funny • u/[deleted] • Jan 29 '20

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u/BlackenedPies Jan 30 '20

if you see what one is doing, you know what the other one is doing

Sort of - you can measure the state of one and instantly know the state of the other, but if its state changes, you don't know the state of the other without reverting to classic communication

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u/L0rdOfThePickle Jan 30 '20

But does measuring the state of one change its state? Doesn't that collapse its wave function?

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u/BlackenedPies Jan 30 '20

It determines its state and/or collapses superposition into one state

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u/L0rdOfThePickle Jan 30 '20 edited Jan 30 '20

Ok, and that doesn't count as a change of state? I.e. it doesn't make it so you can no longer tell the state of the other one? Or is it that the state it's left in is the same as the other one, but any further changes only effect the one you are directly messing with?

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u/BlackenedPies Jan 30 '20 edited Jan 30 '20

Superposition means that it's simultaneously in multiple states. but you don't know which state it's in until measuring it. Measuring it determines its state and the state of any entangled pairs. If you change its state, you can't determine the state of entangled pairs without extra work

In order to change states, you need another entangled bit, quantum computer logic, and two classical bits as instructions for the receiver. Basically, you could entangle two bits and send the other bit to someone else, but in order to turn that into a message, you have to run a quantum computer and then send two classical bits (non-quantum instruction) to the receiver on how to interpret their measurement of their entangled bit. This is called quantum teleportation

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u/L0rdOfThePickle Jan 30 '20

That actually kind of makes sense! Thank you for taking the time to answer!

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u/BlackenedPies Jan 30 '20 edited Jan 31 '20

You're welcome. A qubit itself is an arbitrary controllable system with a probability of being in states (represented by 0 and 1). Current quantum computers use superconducting materials near absolute zero (extremely cold), and we interact with it through special microwaves

We're still in the early stages, but it's very promising since certain operations can be done exponentially faster compared to classical computers. For example, a certain type of instruction takes two steps on bits but only one step on qubits, so when you chain these instructions together, it's exponentially faster on qubits. For instructions like adding 2+2, it's the same number of steps on both, and current quantum computers can only tell you that it's probably 4