How to test the “quantumness” of a quantum computer?

I posted this question in the forum of IBM quantum Experience web site :

How to test the “quantumness” of a quantum computer?

As Quantum computer would be first accessible via the Cloud, I wonder if there are existing tips & tric to test the “quantumness” of my programs and if they really run on a real Quantum hardware and not a simulator…

Seems to be an attractive and shared interest with the community has the statistic of the post are quit important


What the community told us

  1. I noted the terminology of one guy : is like a “turing test” for a quantum computer 🙂

  2.  We have to create non-classical states, for example entangled states and perform measurements to show that these states are not behaving classically.  There are examples of this in the tutorial.

  3. The standard way to test the quantumness of a general system is to carry out the Bell test (see section III.4 in the Library)

  4. You only need to do the Bell test for a large enough system, then no classical simulator can compete in preparing the entangled state of >50 qubits

  5. you could try to do some sort of integer randomness test with outputs from a thoruoughly entangled code?

  6. The other way to verify ‘quantumness’ is to run a sequence of a hard algorithm, where every next iteration is double the problem size of the previous iteration.  If you see the running time only increase linearly then you have an indication the hardware is indeed using quantum resources.

  7. I don’t believe you can, practically speaking. They already have an ideal simulation of it, the difference between a simulation of something and the real thing is the error involved

  8.  Although, the idea proposed by simon_yin of doubling the problem size for each next iteration could work.   Nice discussion!

  9. your answer is almost perfect, but quantumness is not about “randomness”, is about “correlations”, “tunneling” and other features.

  10. Classical systems can be random, while we do not forget the deterministic nature of quantum computing –you beforehand know all the resulting matrices in a product (and time evolution is unitary until measuring the whole quantum system). The error of measurements is not the guide we need, so noise isn’t a clue as important as we can think. The pattern of quantum results is what makes sense to classify them apart from classical systems outcomes. Randomness is the preferred feature of cheap books about “quantum and sciences”, but written from an amateur sight (closer to journalists than to scientists). If I’m wrong, Bernoulli family should have been awaiting Planck’s birth to develop the mathematical statistics, joining forces with Chebyshev, Laplace and other thinkers.

  11.  I guess I was not clear.  I realize that the unitary evolution of an initial quantum state is deterministic up to the point of measurement.  But randomness occurs at the point of measurement.

Finally IBM guys answer with their proposal :

Hi @yannallain this is a hard question. The method we like is the quantum volume. Check out @levsbishop video here for a brief overview. There is a technical white paper that can be found here.

Source of all detailed discussion

The Double Slit experiment with hacker style :-)

Wave & Particles behavior experiments with style (Hacker & DIY mode on)

Could help to understand why a “Quantum bit” (or for short a “Qubit”) could be a “more powerful” hardware support to leverage computing as it’s rely on quantum mechanic behavior – Qubit = more than one state at a time !

Today, I wish to share with you my last experiment about my beginning journey to the understanding of quantum mechanic and quantum computing domain. May be you  already known that everything in the Univers could behave as a Wave and as a Particule at the same time. And ,as far I understand, each peaces of matters in the univers could behave like that until we observe it ! Those “small particules behavior phenomena” seems to be one of the fondamental aspect of quantum mechanic (again,  as I understand it for now)

OK… but How to verify that ? here is come the “Double Slit Experiment” but, as a security guy, we will try to conduct this experiment with….style

  • and more precisely …. with a hacker and Do It Yourself  mind style.


In fact , many of you should have heard or read that light is composed of small particule call “photons”.

 Thus, if I send a bunch of photon (whit a laser?) again a wall… you will see  a small spot on the wall. see on the right…

Nothing strange…for now…


But if we send this laser beam through a double slit made with a cutter on a solid paper (left on side below)…with a very  technical and expensive experimental tools with Word wide scientific precision  🙂







What would be the result on the wall after the light of the laser beam pass trough the double slit ?

Strange and non intuitive things arise here : You will see this on the wall

What’s going on with those crazy photons ? it seems that light behave as a wave !? (as we see interference pattern which , if I refer to littérature available on internet, is a fondamental behavior of a wave !

How it works?

(image of this simulation of those crazy photons behavior found on Wikipedia)

Thus, we could conclude that a laser beam (light) behave some time as a particule (the spot) and sometime as a wave (through the double slit)

Welcome in quantum word !

But believe me (or not) this could help us to designed a new type of computer : A quantum computer… and this experiments works if you send ELECTRON through a double slit instead of light

For all readers, we recommande to watch a complete scientific explanation done by Jim Al-Khalili presented at the royal institution in 2013 (Best Video I watched about this experiment)

Reference of this experiment is related to the work of a scientific, as mentioned by wikipedia as follow :

”  A simpler form of the double-slit experiment was performed by Thomas Young in 1801 (well before quantum mechanics). He believed it demonstrated that the wave theory of light was correct, and his experiment is sometimes referred to as Young’s experiment”

Note: this article was written in listening of “Coming Back to Life ” from Pink floyd… perfect match for those weird stuff 🙂


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