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I tried to look for the resource constraints but so far haven't been able to find them. They are not present in the GitHub repository that usually provides the hardware information for the different devices.

I mean resource constraints as in:

  • Can any single qubit gates be applied on different qubits simultaneously?
  • Can any two-qubit gates be applied on different links simultaneously?
  • Can measurements be performed on different qubits simultaneously?
  • Combinations of the above, etc.

Additionally, I'd also like to know the duration of the measurement operations.

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  • $\begingroup$ When you say "applied/performed on different qubits/links simultaneosly", would it be similar to having these things done in parallel? For example, would it be synonymous to your first bullet point to say "Can any two or more, single qubit gates be applied on two or more different qubits in parallel?" I just want to make sure I fully understand the questions you have on the resource constraints $\endgroup$
    – Matthew Stypulkoski
    May 30, 2019 at 18:56
  • $\begingroup$ Yes, that's what I mean. In the case of superconducting qubits for example, due to a limited number of frequencies at which to park the qubits etc, we may not be able to perform different gates on different qubits in parallel (unless we got as as many frequencies as qubits). This paper: arxiv.org/pdf/1612.08208.pdf reflects a big on a similar issue. As for the measurements, in Qiskit, when I try to perform readout on all qubits at the same time, and draw the resulting circuit, the drawing makes in look that the operation are serialized and not parallel. $\endgroup$
    – Kelthar
    May 30, 2019 at 20:25
  • $\begingroup$ In the case of IBM Q16 Melbourne, it is stated that 'Each qubit has a dedicated CPW readout resonator attached (labeled as R) for control and readout. ', so I supposed the qubits can be controlled independently? $\endgroup$
    – Kelthar
    May 30, 2019 at 20:57
  • $\begingroup$ I believe the measurement operations are drawn in series due to aesthetic considerations, i.e. to avoid overlaps. $\endgroup$
    – Junye Huang
    Aug 5, 2021 at 7:43
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    $\begingroup$ For the latest IBM Quantum systems, the qubits are designed to have 3 different frequency ranges and arranged in a heavy hex lattice to reduce crosstalks. You can read here for more details: research.ibm.com/blog/heavy-hex-lattice $\endgroup$
    – Junye Huang
    Aug 5, 2021 at 7:48

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I think the answers for all the questions are yes, they are possible. Of course that won’t be possible if the gates you want to operate simultaneously act on same qubits, for example, single qubit gate on Qubit 0 and two qubit gate on qubit 0 & qubit 1.

How one enforce such simultaneous operations is a different question. If you use Qiskit Pulse, you can specify the duration of the gate pulses and measurement pulses to achieve the intended effects.

Interestingly, in the upcoming OpenQASM3, it’s possible to achieve alignment of gate and measurements using “glues”, a technique used in TeX for solving similar alignment problem. You can see page 27-30 of the OpenQASM3 for details: https://arxiv.org/abs/2104.14722

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