How Does a Quantum Computer Work?

How Does a Quantum Computer Work?

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A quantum computer works in a totally different way from a classical computer. Quantum bits or ‘qubits’ can exist in a superposition state of both zero and one simultaneously. This means that a set of two qubits can be in a superposition of four states, which therefore require four numbers to uniquely identify the state. So the amount of information stored in N qubits is two to the power of N classical bits.

Thank you to Andrea Morello and UNSW. For more info, check out:


  1. Samir Patel on December 19, 2019 at 7:27 pm

    I lost him when he uttered the first letter “A”……

  2. Matt O on December 19, 2019 at 7:29 pm

    So Qbits can store & process more data in less steps cuz they are exponentially more efficient – compared to classic cpu bits? (When scenario calls for benefit of quantum superposition – like running enormous algorithms??)

  3. RealTerm on December 19, 2019 at 7:30 pm

    Top explanation even for me as physisist !!!

  4. ckurac 1 on December 19, 2019 at 7:31 pm

    I still dont understand how normal pc work…i mean i enter my name and how it can know from 0 1 what is what

  5. Venus Aawtani on December 19, 2019 at 7:31 pm

    Thanku sir, it was very informative

  6. Javier oliva on December 19, 2019 at 7:32 pm

    Thanks for this easy and at the same time deeply explanation !

  7. Rene Lopes on December 19, 2019 at 7:33 pm

    Does brain work like a quatum computer?

  8. lol on December 19, 2019 at 7:35 pm

    Damn that chest hair

  9. William Vick on December 19, 2019 at 7:37 pm

    So then what sorts of tasks exactly would a quantum computer have an advantage in performing?

  10. Paul marsh on December 19, 2019 at 7:39 pm

    Does your quantum computer come with Windows preinstalled?

  11. dekotu on December 19, 2019 at 7:40 pm

    I guess my mind is a classical bit, because it only exists in the state of not understanding this.

  12. arvindra singh on December 19, 2019 at 7:40 pm

    This is my research, (1.5 state)

  13. Hafez Mousavi on December 19, 2019 at 7:42 pm

    It’s actually a solution that scientists are seeking for the NP problems…

  14. The Whisperer on December 19, 2019 at 7:43 pm

    Please tell me whether the point below is correct or not.
    If there are 2^n bits to be processed, the classical computer is supposed to process it one by one, thereby making it impossible for it to do a scale of calculation where n=300+. But in the Quantum computer, it processes the whole 2^n bits in one go. That’s why the processing time is way shorter? Isn’t this true? In theory of course, but isn’t this the case?

  15. Barnaby Wilde on December 19, 2019 at 7:43 pm

    it all boils down to "42"

  16. Isabelbeau on December 19, 2019 at 7:46 pm

    3.45 , he was so proud of his statement !

    Basic terms explained
    Great video 👍

  17. Mike Price on December 19, 2019 at 7:46 pm

    I think this is what I’ve been looking for

  18. Fire Dude on December 19, 2019 at 7:47 pm

    If I understand this correctly; quantum computing isn’t about how fast you can send a normal command, it’s about how efficiently a large command can be sent, resulting in the equivalent of multiple traditional commands being sent in one quantum command?

    I think I’m even more confused because I tried to make sense of this but hey, you can’t have quantum computing/mechanics/physics without first having more aneurysms than you do blood vessels am I right?

  19. Dominic Bouchier on December 19, 2019 at 7:47 pm

    I make money changing words on Wikipedia and travelling to proposed creators of inventions.

  20. Andre on December 19, 2019 at 7:48 pm

    Qubits are like Epstein.
    Someone suicided him.

  21. Puneet Singh on December 19, 2019 at 7:48 pm

    You said magnetic field is spin but in neutrons is there magnetic field or spin?

  22. George Brooke on December 19, 2019 at 7:52 pm

    So a 300 qubit computer could simulate more than the number of particles in the universe! So is that what we are in….just running in some simulation until they get it right? And, BTW, who are "!they"?

  23. Nikola Ns on December 19, 2019 at 7:52 pm

    Does being in different states at the same time require a visa?

  24. B M on December 19, 2019 at 7:54 pm

    That’s the first time I’ve ‘got’ how quantum computers work. -‘it’s not the speed of the individual operations, it’s the number of operations it takes to reach the result.’ No magic. Andrea is a superb scientist. I love his explanations. Thank you!

  25. Dimitar Donev on December 19, 2019 at 7:55 pm

    That’s such a backwards way of explaining quantum computers… We should first start with stating the problems we are trying to solve and why the classical computers fail. Trying to solve the Shrodinger’s equation for an atom more complicated than a hydrogen atom – you have to track interaction between so many quarks and electrons that the time complexity of the algorithm solving the equation grows as O(n!) where n is the number of quantum particles in the system. 20! is already such a big number that it takes months for the equation to be solved, and 100! is simply impossible – even if you set all of the computers available at the beginning of the time they will fail to compute the position and the energy of a quantum system consisting of 100 quantum particles. So here enters quantum computer or a quantum simulator where you have these particles available to you directly so you can manipulate them, put them in certain state, then let them interact and then directly measure their state instead of simulating it with a classical computer. How do you go from tinkering with Q-bits to simulating real world quantum systems – enter quantum algorithms which essentially make the translation to and from Q-bits interaction to real world quantum system interaction. So that ladies and gentlemen is the quantum computer and the very reason it exists.

  26. labg27 on December 19, 2019 at 7:55 pm

    Finally!!! I get it!!! Prof. Morello’s explanation is simple and elegant. Thank you! 🙂

  27. Nauman Shakir on December 19, 2019 at 7:55 pm

    Best explanation ever!

  28. Ricky Rick on December 19, 2019 at 8:00 pm

    When you get it working let me know.

  29. Puneet Singh on December 19, 2019 at 8:02 pm

    Please tell me

  30. SunnyDays Ahead on December 19, 2019 at 8:03 pm

    So ot kinda sounds like quantum computing is better run on common core math rather than english math

  31. Love Kush on December 19, 2019 at 8:04 pm

    Normal computers works on Transistors / quantum computer works ion electrons outerside of atom

  32. Robert Hunt on December 19, 2019 at 8:05 pm

    I found the answer to Quantum Computing: 01010100 01101000 01100101 00100000 01100001 01101110 01110011 01110111 01100101 01110010 00100000 01101001 01110011 00100000 00110100 00110010

  33. dejohnny2 on December 19, 2019 at 8:06 pm

    For some strange reason I understood everything he was saying.

  34. Shedhead on December 19, 2019 at 8:07 pm

    Camera person pissed?

  35. Atlas Shocked on December 19, 2019 at 8:08 pm

    Most important thing said was near the end, where prof said for most common applications now, like surfing internet, or word processing, quantum computer would be slower, so its not a replacement for classical computers. But, that is now…..

  36. JohnKouts on December 19, 2019 at 8:10 pm

    Thank you for the bad explanation

  37. Qiu Hailu on December 19, 2019 at 8:12 pm

    why electron spin down for the lowest energy state? I thought it should spin up when it aligns with the magnetic field.

  38. ноу ноу on December 19, 2019 at 8:12 pm

    0:42 – опааа, Джайро одобряет, тупа ньюююхо, шо

  39. blinkin on December 19, 2019 at 8:13 pm

    i am having trouble seeing the difference. the amount different states for a normal processor is already 2^n, the explanation of Qbits here seems to just repeat that.

  40. Manas Hejmadi on December 19, 2019 at 8:13 pm

    Are all intelligent people left handed?😂

  41. Jason Carmichael on December 19, 2019 at 8:15 pm

    53 qbit google computer (and 1 dud)

    9,007,199,254,740,992 calculations.
    Answer found in 200 seconds.
    Classical computing would take 10,000 years.

    "How do we know that is the right answer?" – "It must be."

  42. Bryyy Raiz on December 19, 2019 at 8:16 pm

    Are we taking a test after this video?

  43. ADdas on December 19, 2019 at 8:17 pm

    If i had two electrons having any of the 4 combinations and named each combination a,b,c and d respectively, then does "superposition of each one of these 4 states" mean that a, b, c and d will superimpose or that , lets say in d, the two spins could superimpose?

  44. Stanley Plock on December 19, 2019 at 8:17 pm

    That’s nice. Every video says the same things.
    BUT… How do you:
    1. Input data
    2. Output data
    3. How the heck does the "computing" work?
    Is there some sort of Program that needs to be written.? Or is it some magical thing that can’t be explained?
    Does it work something like a OUIJA Board?

    Elon Musk and Gordie Rose mention "an alter to an alien god". Is this somehow connected to the Matrix or Universal Consciousness?
    What David Wilcox calls the "Source Field"?
    Similar to what savants are connecting to?

    What are they NOT telling us about this "alien god"?
    My best guess is that it works like an OUIJA board but connected to a much higher level of consciousness and not just the lower astral demons. I would assume you "talk" to this "alien god in ASCII and the output is in ASCII and it most likely would understand different languages since it has no "program" as conventional computers do.

    If you understand how the lowest level of machine code works, you must realize that this is something very outside the "normal" physics of conventional computers. It’s magic! Possibly metaphysical in nature.
    Is "alien god" just a metaphor, or is it to be taken literally?
    What exactly is artificial intelligence?
    And why are they not telling us?

  45. Arietris on December 19, 2019 at 8:18 pm

    So basically in quantum computer’s processors are particles in superposition, but when measured they give you one stare or another?

  46. John Bates on December 19, 2019 at 8:22 pm

    Thank you for explaining quantum computing in another way, which I also do not understand. It would be helpful if this were brought this into the real world by describing what is physically measured, what it is measured by, what the readout is, how this measurement is done, and why these measurements allow processed that are exponentially faster, to be measured. Is that too basic or boring for you? Will it mean that you won’t be able to use the term quantum entanglement for a short time?

  47. Mike Astro on December 19, 2019 at 8:23 pm

    0:11 It is NOT 0 and 1 at the same time. It is 0 or 1, but we can not say which one because it alternates its state rapidly.

  48. นาย โชคดี ทุกวัน on December 19, 2019 at 8:25 pm

    Using the left hand means very smart

  49. kitkatcats on December 19, 2019 at 8:26 pm

    I believe these guys, but sometimes I wonder if they’re just punking us because most of us (me for sure) don’t know enough to question it.