• Question: What do you see as the potential real world uses of quantum computing? What difference would it make to students’ lives, for example?

    Asked by Robert to Ieva on 12 Jan 2020.
    • Photo: Ieva Cepaite

      Ieva Cepaite answered on 12 Jan 2020:


      This is possibly one of the most-often-asked questions I’ve heard from people – for obvious reasons. Quantum Computing, as a technology, has had a very weird development historically.

      When classical computers were first built, we only had some notion of what they could be used for and over time, along with developing technology, we discovered things like machine learning and language processing and many more. With Quantum Computers, the development of the machines themselves is very slow, but the theory focusing on what they COULD be applied to is going ahead a breakneck speed making it difficult to gain a reasonable idea of what they’ll actually be used for. Firstly because we don’t know if there’s a bottleneck for the size of a useful Quantum Computer that we can build and secondly because some of the algorithms and protocols that have already been developed have never been tested, so there is an argument to be made that some of them might never work in practice despite the promise they hold.

      That is not to say that we don’t have a fairly clear idea for applications that seem reasonable to implement in the next couple of years/decades! One of the simplest to explain and that has consequences for the real world is the simulation of complex molecules and quantum systems. This is stuff we can use to improve research in material sciences, development of drugs and many other fields that need a very accurate description of the physics of atoms and molecules – a description that classical computers simply can’t give because of the immense sizes of these problems.

      For these problems a Quantum Computer is basically just a replicate of the system you want to investigate – say a very large molecule with many electrons that interact in millions of ways – but with a very high degree of control. In that sense, we’re building a quantum system that behaves like what we’re interested in and then we can tweak parts of it (compute) in order to extract information of interest. All the complexity of the problem is inherent in the Quantum Computer itself and we don’t need infinite matrices or near-infinite time to compute them as we would in a classical computer. I believe this to be the most likely near-term application of Quantum Computers that will give useful results.

      Then there are things like Quantum cryptography, which I believe will need far larger and more robust Quantum Computers than we can achieve in, say, five years (though I have no reason to think they’ll never exist). In this case, the way that information behaves in a Quantum Computer might be used to break current encryption protocols (see Shor’s algorithm and RSA encryption) or to create new, information-theoretic secure protocols of communication that are physically impossible to break due to things like the fact that interfering with a quantum state during a computation is almost impossible to hide. In this case trying to listen-in on a private communication would be made impossible without detection.

      One of the scariest things about this is that despite years of work, we still don’t have a robust method of dealing with Quantum attacks on classical communications channels. Assuming someone builds a large enough Quantum Computer first and manages to apply it to, say, breaking RSA encryption, we might be powerless against it! And for quantum communication, we’d need both ends of the line to have pretty decent quantum computing power to be able to do it, so it’s a big problem for security around the world. Let’s hope that so-called ‘post-quantum’ cryptography will prevail before a Quantum Computer like that is built.

      There are many more interesting applications, but I think that the above are easiest to communicate and likely to be impactful in the future. I hope this helped!

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