Very general question so I'm not looking for an exact answer.

I just want a basic description of certain ways it can be done and then if possible the names of those ways, so that I can look them up further.

But I want to know, if I was to run some code in a quantum computing language, how would a classical computer interface with the quantum one to instruct it?

Contact the machinery that directly builds a full circuit and then run it? Does it go line by line and apply the gate at each stage? Can it just directly communicate with the qubits?

Note: I am looking for answers for both gate based and continous computing


1 Answer 1


It would be really platform specific - for example, suppose you have a quantum program ready using some gate set. But, the quantum hardware you have implements a different set. Well, you'd need to convert from your original gates into a new set of gates (and potentially perform some optimizations). Overall, this can probably be broken into a few steps:

  1. Prepare a quantum program (Q#, Qiskit, etc.)
  2. Compile into the device's gate set (RZ, X, etc.)
  3. Convert gates into hardware instruction (Laser pulse of XYZ with frequency ABC, for example)
  4. Report results mechanically (e.g. measure qubit) and return to operating machine

Here's an example of how Q# thinks of the classical/quantum interaction. What we discussed occurs between "Q# operation" and "Target machine." Q# architecture

  • $\begingroup$ Okay, so Im guessing with laser pulses one its theoretically possible to send one instruction at a time? Like in a console? (not that I can think of a good reason to do that). Is there an example of a type of QC where that would be impossible? Where code taken is used to construct a full circuit and thats the only way? $\endgroup$
    – QurakNerd
    Commented Jul 4, 2020 at 10:05
  • 1
    $\begingroup$ My understanding is that compiling all the instructions in advance actually is better because this reduces the total amount of time needed to execute a program. Not just because you want the program to run for less time, but also because it reduces the risk of decoherence. So, the hope is a chip that controls the physical hardware is able to store all the instructions to minimize latency $\endgroup$
    – C. Kang
    Commented Jul 4, 2020 at 13:18
  • $\begingroup$ Yes that makes sense. I just wondered if there are alternatives. Final question while its still kind of related to my original question, are there alternatives to laser pulses in quantum computing? $\endgroup$
    – QurakNerd
    Commented Jul 4, 2020 at 19:35
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    $\begingroup$ Yes- there are many different types of quantum computing. Each has their own physical method of interfacing (for example, one might need microwave pulses, another might use some other weird way to manipulate the qubit, etc.) $\endgroup$
    – C. Kang
    Commented Jul 5, 2020 at 2:53

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