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I'm a university student and as an introduction to a project in a course, it is needed to investigate about estimating the amount of money and funding to start making infrastructures for fabricating different kinds of qubits.

So, I have so much searched through the net but can not find some satisfactory results. anyone can help, please?

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Well, that's your project, isn't it! I'd start by looking up which kinds of things can be qubits, and then what's required to make each of those, and then how much those techniques cost.

For example - this is totally made up for illustrative purposes and I have no actual idea how to make a qubit - perhaps a superconducting qubit requires a small ring of superconductor with a Josephson junction. That requires superconducting material, a way to make it into a small ring*, cooling**, a suitable material for the junction, a way to calibrate the thickness of the junction, and a coil to couple electrical impulses into the ring.

Then you go even deeper: what superconductor material can be made easily and doesn't require liquid helium temperatures? How can it be made into a ring shape - will standard metal-machining processes do? Humans already know how to make shapes out of metal. Is liquid nitrogen cold enough, or do you need a cryo-cooler (which you can probably buy from a specialized company and don't need to design yourself)?

You said the cost to make "infrastructures for fabricating" the qubits and not the cost for the qubits themselves. So: what equipment is needed to make and shape that superconductor material and those junctions? (remember that this example is made up as I don't know how qubits can be made)

Since you said "introduction" and "estimating", I suspect that shortcuts are acceptable to avoid spending a really long time. E.g. a lot of experiments need a cryo-cooler, so I guess there are companies that will make one, but they won't sell many, so it's probably made to order, so maybe it's in the range of $10000. It would be better to find an advertisement from a company that makes cryo-coolers, but if you can't find one, it might be okay to guess. And maybe instead of looking at how to make superconductors you can just look at the cost of other superconductor experiments. Maybe you can ask your instructor how accurate your work needs to be.

Good luck!

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    $\begingroup$ Just FYI (not a critique of your answer) superconducting qubits have to be much colder than their superconducting transition temperature, so they're basically never in the "liquid nitrogen" regime and always in the "hard to cool" regime. The basic reason is that you need more than superconductivity, you also need to not accidentally go into excited states. The energy gaps are around 50 mK, so you need to be significantly below 50 mK to stay in the ground state of the superconducting circuit. $\endgroup$ Sep 14, 2022 at 18:42
  • $\begingroup$ Thanks @user253751 for your answer. as I said in the comment for the previous answer, I have got the same approach but it takes too time. anyway, thanks for your help. $\endgroup$
    – P.A.M
    Sep 15, 2022 at 6:34
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It will depend somewhat on the way in which you are encoding information. There are different types of devices that serve as physical qubits. I think a good strategy for your work might be first selecting phyisical qubits of interest, later understanding what are the minimal experimental requirements to implement those and finally, once you have selected the devices you can look for companies that sell them. Here are some (incomplete list of) ways to implement physical qubits

  • An NV-center can be used as a physical qubit.

  • Single-photons can serve as physical qubits, encoding information in polarization, path, time-delay, etc.

  • Superconducting islands coupled with Josephson junctions can serve as qubits.

  • Trapped ions can serve as qubits.

Now, you can try to map what you need for making at least some noisy not so great qubits. For instance, in the photonic implementation you will need a single-photon source, some single-photon detectors, optical fibers, at least two beam-splitters and maybe two phase-shifters.

Finally try to look up how much it costs any of these looking for some range of prices. The hint therefore for sources might be companies products, etc. This is just an example. Here are for instance single-photon sources by Quandela; they also have some basic tutorials. Here is the company website of Thorlabs that also sells optical components.

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  • $\begingroup$ Thanks @R.W. Actually the way you explained is the way I tried to look for the solution. But, you know, it is so time consuming and also incomplete. because it needs you to be expert in the field to recognize what is what and where to search and what to search about different kind of qubits. at least in one field you should be expert I think. It is possible but time consuming. $\endgroup$
    – P.A.M
    Sep 14, 2022 at 8:19
  • $\begingroup$ I totally understand. Good luck in your work, I think with the devices I told you about it should provide at least a 'lower bound' on the cost. It is a great question. $\endgroup$
    – R.W
    Sep 14, 2022 at 8:23
  • $\begingroup$ @P.A.M I think that is why it's an investigation, not just a Google search! $\endgroup$
    – user253751
    Sep 14, 2022 at 14:46

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