4 ms·

It wouldn't be that insane for a factory to be able to create so many qubits. Building one qubit is hard, building two qubits is not double the effort.

by bArray 5y ago

thebean11 5y ago
I think the difficulty is putting them into one processor
ALittleLight 5y ago
My, highly imperfect, complete layman understanding is that the challenge has nothing to do with the "manufacture" of qubits, but rather getting them to work in the same computer without interfering with each other. I believe it gets harder with each qubit, not easier.
- shepherdjerred 5y ago
  Is it possible to scale it by building separate computers and using distributed computing techniques? e.g. would 100 1 qubit computers be equivalent to a single 100 qubit computer?
  - d_tr 5y ago
    The set of qubits needs to be an isolated system while the quantum computation happens, so no. By taking the qubits apart you would only make this much harder, if not impossible.
  - ben_w 5y ago
    No. Most of the benefits of quantum computing requires the qbits be entangled with each other, so, crudely speaking, the difference between 100 (1-qbit-computers) and 1 (100-qbit-computer) is ability to compute using the 2^100 different ways the latter qbits can be entangled.
ninkendo 5y ago
Right, and I don't understand why it took the industry so many decades for 64-bit computing to become dominant. If a factory is creating bits, it shouldn't take 64x the effort to create 64 of them versus 1 bit...
- bArray 5y ago
  64 bit computing became dominant because of the need to address memory larger than 32 bits. They have the capability to scale quite 'easily' to 128 bits or further if they wanted to, there just wouldn't be a benefit. The Play Station 2 for example has 128 bit SIMD [1], 128 bit computing has been possible for a long time. Once you have the ability to create a processor at 7nm with some bits, scaling is not so tough. Even if you cannot reliably create larger pieces of silicon, you just do something like AMD did with multiple dies connected by a fabric to mitigate risk. Absolutely worst case, you have a motherboard with multiple processors, or even computers in different buildings. In terms of qubits, it is very likely that the problem can be distributed over multiple quantum computers. A significantly incentivized actor could definitely pull it off. If you can reliably manufacture ~100 qubit quantum computers, it's just a matter of scale. [1] https://en.wikipedia.org/wiki/PlayStation_2_technical_specifications#Central_processing_unit https://en.wikipedia.org/wiki/PlayStation_2_technical_specif...
  - tsimionescu 5y ago
    > In terms of qubits, it is very likely that the problem can be distributed over multiple quantum computers. No, this is very wrong. Qubits are only different from classical bits of they can communicate before becoming entangled with the environment (decoherence). You can't run some kind of "quantum cable" between two separate QCs in a rack and get twice the qubits - the interactions with the wire will break the entanglement between the qubits, and you will just have an unreliable classical computer with 100 bits of memory. To perform a quantum computation, ALL the qubits (all your memory) must be in an entangled state together - this is the massive problem. Even worse, this state must be maintained while applying different transformations on the qubits from the outside.
    - 5y ago
tsimionescu 5y ago
> Building one qubit is hard, building two qubits is not double the effort. No, it's much, much more than double the effort to build a QC with twice the qubits. The problem is that you want the qubits to interact with each other, but to be entirely perfectly isolated from the outside world for as long as necessary for signals from one to reach the others. The difficulty of achieving this isolation even for an instant at all increases by something like n^2 or n^3 (surface/volume of the isolated space) with the number n of qubits. Then, the more qubits you have, the more time you need for them to interact, so you multiply by an additional factor. The numbers above are very handwavy, of course, but the point is that it's MUCH harder to build a bigger QC than a small one. So hard that it's not even clear if the current approaches can actually achieve this even in principle - we may need a different kind of qubit to scale up.
deleted 5y ago
[deleted]

It wouldn't be that insane for a factory to be able to create so many qubits. Building one qubit is hard, building two qubits is not double the effort.

by bArray 5y ago

It wouldn't be that insane for a factory to be able to create so many qubits. Building one qubit is hard, building two qubits is not double the effort.

thebean11 5y ago

I think the difficulty is putting them into one processor

ALittleLight 5y ago

My, highly imperfect, complete layman understanding is that the challenge has nothing to do with the "manufacture" of qubits, but rather getting them to work in the same computer without interfering with each other. I believe it gets harder with each qubit, not easier.

shepherdjerred 5y ago
Is it possible to scale it by building separate computers and using distributed computing techniques? e.g. would 100 1 qubit computers be equivalent to a single 100 qubit computer?
- d_tr 5y ago
  The set of qubits needs to be an isolated system while the quantum computation happens, so no. By taking the qubits apart you would only make this much harder, if not impossible.
- ben_w 5y ago
  No. Most of the benefits of quantum computing requires the qbits be entangled with each other, so, crudely speaking, the difference between 100 (1-qbit-computers) and 1 (100-qbit-computer) is ability to compute using the 2^100 different ways the latter qbits can be entangled.

ninkendo 5y ago

Right, and I don't understand why it took the industry so many decades for 64-bit computing to become dominant. If a factory is creating bits, it shouldn't take 64x the effort to create 64 of them versus 1 bit...

bArray 5y ago
64 bit computing became dominant because of the need to address memory larger than 32 bits. They have the capability to scale quite 'easily' to 128 bits or further if they wanted to, there just wouldn't be a benefit. The Play Station 2 for example has 128 bit SIMD [1], 128 bit computing has been possible for a long time. Once you have the ability to create a processor at 7nm with some bits, scaling is not so tough. Even if you cannot reliably create larger pieces of silicon, you just do something like AMD did with multiple dies connected by a fabric to mitigate risk. Absolutely worst case, you have a motherboard with multiple processors, or even computers in different buildings. In terms of qubits, it is very likely that the problem can be distributed over multiple quantum computers. A significantly incentivized actor could definitely pull it off. If you can reliably manufacture ~100 qubit quantum computers, it's just a matter of scale. [1] https://en.wikipedia.org/wiki/PlayStation_2_technical_specifications#Central_processing_unit https://en.wikipedia.org/wiki/PlayStation_2_technical_specif...
- tsimionescu 5y ago
  > In terms of qubits, it is very likely that the problem can be distributed over multiple quantum computers. No, this is very wrong. Qubits are only different from classical bits of they can communicate before becoming entangled with the environment (decoherence). You can't run some kind of "quantum cable" between two separate QCs in a rack and get twice the qubits - the interactions with the wire will break the entanglement between the qubits, and you will just have an unreliable classical computer with 100 bits of memory. To perform a quantum computation, ALL the qubits (all your memory) must be in an entangled state together - this is the massive problem. Even worse, this state must be maintained while applying different transformations on the qubits from the outside.
  - 5y ago

tsimionescu 5y ago

> Building one qubit is hard, building two qubits is not double the effort. No, it's much, much more than double the effort to build a QC with twice the qubits. The problem is that you want the qubits to interact with each other, but to be entirely perfectly isolated from the outside world for as long as necessary for signals from one to reach the others. The difficulty of achieving this isolation even for an instant at all increases by something like n^2 or n^3 (surface/volume of the isolated space) with the number n of qubits. Then, the more qubits you have, the more time you need for them to interact, so you multiply by an additional factor. The numbers above are very handwavy, of course, but the point is that it's MUCH harder to build a bigger QC than a small one. So hard that it's not even clear if the current approaches can actually achieve this even in principle - we may need a different kind of qubit to scale up.

deleted 5y ago

[deleted]