Quantum Physics, Computing & Cybersecurity

 

The blog is transcribed and summarised from the podcast, hence the lack of grammar, syntax and semantic formality.

In this blog, we are going to tackle the concept of quantum physics and its relationship and possible implications to computing, cybersecurity and data privacy. The subject matter is very daunting, but we will do our best to break it down into relatable notions. 

Quantum physics is the science of the very, very small. It is the study of particles the size of atoms or smaller. In the quantum realm, things are bizarre, to say the least! We are used to working with Newtonian physics in the classical sense, matter is either a solid, liquid or gas, it exists in both time and space and is affected by gravity, electromagnetic and nuclear forces in predictable and intuitive ways. However, when you delve into the quantum world, you realise that your perception of reality is extraordinarily different to its true nature.  

Atoms and sub-atomic particles are unimaginably small, with sizes measured in nanometres and angstroms, that is one ten millionth of a millimetre; and this is where classical physics breaks down. To delve further into the ‘weirdness’ of the quantum realm, we will talk about the variations of the double-slit experiment, which is the gold standard in ‘how weird is quantum’ experiments.  

The Double-Slit Experiment 

Is light a wave or a particle? That debate has continued to rage since 1630 when Rene Descartes argued that light was a wave and not, as commonly believed at that time, a particle.  

171 years later Thomas Young provided some evidence of this when in 1801 he began work that ended with the now famous double slit experiment. A modern explanation of which is described below. 

Consider the following image: – 

 

Singular light source hitting a screen

The diagram shows a singular light source hitting a screen with two vertical slits, the light shines through both of those slits. You may expect to see two vertical lines of light on the back screen. However, as you can see in the diagram, that is not the case. The result is that we get multiple bars that are not clearly defined i.e., they are fuzzy. These bars are called interference bars. It makes sense when you consider light traveling as a wave, as 2 waves would be created by the 2 slits and interfere with each other prior to hitting the screen. Analogous to if you throw 2 stones in a pond and see the ripples collide, image below. 

Quantum mechanics rule 'bent' in classic experiment - BBC News

The idea that light travelled as a wave persisted until 1905 when Albert Einstein shook up physics with a paper claiming that light was composed of indivisible quantum particles, or quanta. He used this theory to explain, amongst other phenomena, the photoelectric effect. In short, the photoelectric effect states that light can affect electrical conductance. 

So, we had a conflict, Descartes and Young on one side, and Einstein on the other. Seemingly as a compromise, the phrase wave-particle duality sprung into existence, popularised by Danish physicist Niels Bohr in 1928. Later Louis de Broglie suggested that if light can have wave-particle duality, perhaps matter could too. More experiments followed that suggested de Broglie was correct, and when interpreted by Erwin Schrödinger, Werner Heisenberg and Paul Dirac they formed many of the quantum physics theories we use today. Broglie et al’s work indicated that an electron beam would create the same interference bar as light in the double slit experiment. More weirdly, they also successfully predicted that if the electron beam was reduced to emit only a single electron at a time, with a pause before the next one was emitted, then the interference pattern would still be observed as the backplane recorded each individual electron hit over time. Think about that, how can a single electron interfere with itself? If that does not give you a headache, read it again, you must be missing something. 

That matter, in this case subatomic particles, could travel in a wave was ultimately proven beyond doubt in 1961 by Claus Jonsson, when he performed a double slit experiment using a beam of electrons. The result, as predicted, was the same interference pattern observed in Youngs light experiments. Thus, Jonsson’s experiment demonstrated that an electron beam too travels as a wave. However, Jonsson lacked the technology to reduce the beam to single electrons. That the interference pattern would still be created when releasing one electron at a time was not practically proven until 2013 by Roger Bach. He performed the experiment as per hypothesis and reduced the beam to emit only a single electron at a time, with a pause of one second before the next one was emitted. Defying intuition, the interference pattern was still observed as the back screen recorded each individual electron hit over time. 

So, to crank the wierdometer up another notch, scientists have discovered that when an electron detector is placed next to one of the slits, to detect which slit it travels through, the interference pattern is not generated. The result is two vertical strips, as if the slits were being used as a stencil with spray paint, the electrons exhibit a nature of particle and not wave. The intuitive reasoning is that the electrons “change” their behaviour when being observed. Whether this is caused by the measuring apparatus, even though it is passive in the conventional sense, or by a conscious mind, is still hotly debated. What we do know is that many variations of this experiment have been performed, and in each case as soon as information identifying which slit the electron went through occurs, the interference pattern breaks down. Personally, I like to think the conscious mind has a bearing on this, and that the universe is very different to how we imagine. 

EPR and entanglement shenanigans  

Another example of quantum weirdness is that certain pairs of particles, such as electrons, can become entangled, which means that the particles act as one complete system. Each of two entangled electrons for example can either be judged to have an up spin or a down spin characteristic when measured, if one is up spin the other invariably will be down spin. Before you measure either of the entangled electrons though, quantum theory dictates that they do not actually exist in either an up or down spin, as it is in a state we call superposition. It exists in both states simultaneously and is not in either state until it is measured or observed. However, once you measure one of the electrons as being up spin the other is instantly revealed as down spin. Insanely these electrons do not need to be near each other. They can co-exist on polar ends of the universe, but if you observe and measure the spin on one of the entangled electrons, it will immediately affect the other. I promise I am not pulling your leg; these are proven facts.  

So, it seems communication between these particles can extend across the entire universe. Einstein called this ‘spooky action at a distance’, and he did not buy into it at all. In fact, he unsuccessfully sought to dispel much of quantum theory for the remainder of his life. But test after test confirmed the theories as correct, and ultimately Einstein died still trying to disprove them. Nobody fully understands it. All we can say for sure is that we have observed that quantum particles exist in more than one state, at the same time and observing them appear to cause a change to a state.  

What effect does all of this have on traditional computing? 

We need to revisit classical computing briefly to see how quantum computing contrasts. In classical digital computing, the smallest unit of calculation is a bit. And a bit can either be zero or one. Bits can be represented as electrical pulses via transistors, where they can be switched on or off. Everything in computing ends up in binary code – consisting of zeros and ones. By contrast, in quantum computing, the traits of entanglement and superposition can be used as ways to form qubits. A qubit can either be zero or one at any given time, like the entangled electron from earlier, before it is measured it is in both states. This does not suggest that the qubit exists in a value between zero or one. The truth is that it is in both a zero and a one state until measured. However various factors can determine how likely a qubit is to be a 0 or 1 when measured, these factors allow for multiple states to be used in calculations simultaneously. This leads to parallel processing on a different level, and thus the potential to be far faster, at solving certain problems than traditional computing. 

The increase of computing power can be very beneficial, but are there any drawbacks? 

Cryptography is an example of that. There are cryptographic algorithms, such as RSA, which use prime factorisation. This works as every composite integer can be written as a product of prime numbers. Calculating these prime factors gets exponentially more difficult as the composite integer gets larger. The difficulty of these calculations is at the heart of RSA and some other cryptographic algorithms. It is easy to go from prime factors to composite integer but not vice versa. If you wanted to crack an algorithm like that, it would require huge brute force power with traditional computing. Effective brute forcing requires performing multiple calculations simultaneously, and with Quantum computing promising so much in terms of parallel and simultaneous processing it could mean the end of these algorithms. Which should be a concern when you consider the petabytes and exabytes of data protected with them. This concern has led to numerous mathematicians working on creating quantum-resistant cryptography. The flip side of the coin is that while some are working on ways of cracking encryption using quantum computing, others are working on how to use it to strengthen cryptography.  

Another concern is with the digital blockchain currency bitcoin. Bitcoin mining is where you use math and complex calculations to mine the Blockchain for Bitcoins. If quantum computing moved to a point of being able to solve traditional calculations effectively, and then applied it to Bitcoin mining, they could become very wealthy, very quickly. Fortunately, or otherwise depending on your views, we are not at that point yet. 

In what ways can quantum computing be used for the benefit of humankind? 

We are talking about a system that can do billions of calculations in parallel. I can imagine us using it in the medical profession to analyse extremely complex data sets and run non-human test scenarios on organoids (lab-grown cells). The power of quantum computing might be used to run datasets on medical data, leading to new treatments of diseases, particularly genetic ones such as Cystic Fibrosis. 

If I were to go way out there; a lot of hype surrounded AI in the past, notably in the 1990s, I dabbled a little myself back then. We recognised the incredible potential AI algorithms and designs had, e.g., those for artificial neural nets; however, we lacked the processing power to fully realise their potential. While we have moved on a long way since then, particularly with the parallel processing power of GPU’s, FPGA’s, and ASICs, AI still has a long way to go. This remains because we have not had the full parallel processing power to make use of it. So, maybe quantum computing is how we will do that. I ponder, we have never had a self-aware machine. But could quantum computing perhaps be the last piece in solving this puzzle? Once we get that type of processing power, is that the point where singularity becomes a reality? Where we get consciousness in a machine? 

There are more questions than answers at this point. And only time and an inordinate amount of patience is needed before the answers are revealed. Rest assured, Samurai are keeping a close eye on this space, and will keep you posted. 

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