The universe (multiverse?) is really weird on the quantum level. The weirdness is real. Extensive testing has found no hidden variables to explain the weirdness in terms of normal macroscopic experience. Meanwhile, humans, as we are wont, are finding ways to use this strange reality. Here, we will describe how this is being done in quantum computing.
We have not yet demonstrated that quantum computers will outperform current semiconductor based computers in any task, but I wouldn’t bet against it. If it does happen, we can be reasonably certain about fields that will be impacted, though the full extent of potential applications is unpredictable, as it is for most emerging technologies. It’s not yet a full blown revolution in progress, like genome editing, but it has the potential to get there in the near future.
To truly understand quantum computing would require advanced degrees in physics and computer science. We’ll do what we can in a relatively short essay written by a biologist with some computer experience and an interest in physics.
First, a quick aside and a bare minimum of background information
The aside is that, when you look closely, the universe is not continuous. It is pixelated. The pixel size is Planck’s constant. So, for example, when electrons orbiting a nucleus become more or less energetic, they jump between orbits. There is no smooth flight between energy level orbits. It’s a quantum transition, with no middle ground. Hence, it’s quantum mechanics.
In order to understand quantum computing, consider how electrons behave. They exist as probability clouds. They are not like tiny spheres zooming around the atomic nucleus. It is not like a satellite orbiting the earth or the earth orbiting the sun. It is not like shaking a stick or swinging a rope that only looks like a blur, but is still an object that is simply moving quickly, but that can be defined in space by knowing how fast you are swinging your arm and where the swinging started. The electron is the blur. There is no math or physics to define it as a point in the blur.
Yes, electrons have specific orbits around atomic nuclei, but the electrons are clouds of probability in those orbits. When you sample that cloud, you will either find an electron or not, with the chance of observing it based on the probability of the electron being in that area of the cloud. In other words, electrons can be observed as point like particles (or defined waves), but when not observed, electrons truly exist as probability clouds.
It’s not just electrons. It’s all particles/phenomena on the atomic scale and smaller, including photons.
A term derived from this reality that is relevant for quantum computing is superposition. That is, quantum things can be in multiple places or states at one time.
Another relevant point is that upon interacting with other things, such as an instrument of observation, the particle/wave being observed collapses to a specific location or energy state. The probability cloud becomes a specific point in the cloud. All of the possibilities become one realization. That collapse of many possibilities into one reality is called quantum decoherence.
Many readers will be familiar with quantum coherence and decoherence in terms of Schrodinger’s cat, wherein a cat in a box containing poison triggered by a probabilistic quantum event will be both dead and alive until the box is opened and then the cat is either dead or alive. In quantum computing, decoherence is undesirable. We want the probabilistic state where the cat is dead and alive until we have finished the computations.
Readers might also wonder what triggers decoherence. Historically, it is known as the observer effect. The outcome is affected by the observer. More precisely, a quantum state collapses upon interaction with a system that distinguishes between potential outcomes. It doesn’t have to be a person looking at a screen. One of the challenges of quantum computing is to isolate the quantum processes from any such interaction. Vacuums and supercooling are employed to minimize interactions and decoherence.
Finally, and very briefly, in addition to incorporating superposition, quantum computing also seeks to utilize the related phenomenon of entanglement, in which seemingly separate particles exist with quantum states that are tied to each other. For example, if the spin states of two electrons are entangled, then, upon measuring the spin of one of the pair, the spin of the other is automatically known. It’s spooky action at a distance, but real nonetheless.
Quantum biology, if it is real, shows that quantum phenomena can have macroscopic effects
In recent years, biologists have speculated that quantum mechanics might be acting in wet, warm and noisy biological systems.
As yet, the efficiency of photosynthesis has not been fully explained by classical physics. On the contrary, the ability of photosynthetic organisms to efficiently transfer energy across complex light harvesting centers has been attributed to superpositioning electrons exploring many paths simultaneously and finding their way across efficient paths. However, it appears that these conclusions might be exaggerated, though quantum effects might still play a part in photosynthetic efficiency.
Perhaps more widely accepted is the notion that enzymes can speed up some reactions by taking advantage of quantum tunneling, which is the observation that, since quantum particles exist as probability fields, there is some chance that they will spontaneously jump across energy barriers that would prohibit reactions in classical systems.
The ultimate effects of quantum mechanics might even affect the behavior of animals. There is some evidence that migrating birds can navigate by measuring magnetic fields using coherent quantum states within recently identified proteins in the eyes of migrating birds.
In short, there are multiple lines of research suggesting that quantum mechanics affects, and might even provide selective advantages for living organisms on macroscopic scales. At this point, the links are compelling, but have not yet been conclusively demonstrated as the best explanation for observed activities.
Finally, quantum computing
Quantum mechanics is real and quite possibly has effects that can be propagated into macroscopic systems. So, what does that have to do with computers? A short and incomplete answer is that we can develop computations based upon probabilities rather than the binary bits comprising semiconductor computers. Rather than binary zero or one bits, we can have continuous zero and one qubits, with the probabilities of zero and one adding to 100%. Plus, we can entangle the qubits to compile long strings of probabilistic information processing.
For better explanations, check out this introduction and/or watch these videos.
The last video showed that, minus design errors, the quantum computer always won the coin flipping game. That’s because the quantum computer can explore the potential outcome space through superpositioning and settle on the best outcome through controlled decoherence at the proper time, in this case, at the end of the game.
This ability to explore the potential space through probabilities is a distinct advantage over semiconductor computers, in which all possibilities must be explicitly defined and separately explored. If decoherence can be controlled and scaled up, this will have huge impacts.
Secrets today, won’t be tomorrow. Secrets tomorrow might stay that way.
Computer cryptography relies on computations that are easy to calculate, but difficult to decipher. Simplistically, cryptography relies on pairs of large prime numbers. It’s easy to calculate the product of the pairs and generate the keys, and everybody knows that breaking the key is based on prime number factors. However, if the numbers are sufficiently large, it will take too long for semiconductor computers to figure out just which prime numbers are used to make the keys, and, therefore, break the encryption. In practice, it’s more complex than that, but it’s still based on factoring large numbers.
With quantum computers, the factor space can be quickly explored and will, therefore, make key pairs based on factoring large numbers obsolete.
On the other hand, quantum computing promises to usher in cryptography that is unbreakable, at least without the rightful sender and recipient knowing that it has been compromised. This is due to the fact that any attempt to intercept the keys will necessarily affect the key through the observer effect.
The potential applications are unlimited
Quantum computers may impact any field in which there is a large set of complex parameters to explore. Development of artificial intelligence may be accelerated through quantum computing. Financial markets already impacted by computer trading will be further disrupted by quantum computing. Traffic flow could be more efficient with incorporation of quantum computing.
One benefit of being able to quickly explore potential solutions will be to exponentially increase the power of simulations. Chemistry research will include more comprehensive reaction models and many more atoms in complex systems. Pharmaceutical research will include large models that will accelerate drug discovery and cover most eventualities, not just a few model types. Climate simulations and weather prediction might be run more quickly with more realistic and complex sets of parameters. Astronomy will be able to model large dynamic systems with many interacting bodies. This promises for increased understanding back to the beginning of the universe.
Some researchers have speculated that quantum computing is simply a subset of what the universe already does. Quantum particles are already doing the computing. The universe might be a quantum computer.
As with any emerging technology, there is a lot of hype. The actual outcomes of quantum computing, if it can be scaled up, remain to be determined.
The current status
The last section had a lot of promises. Here is where we are in early 2019.
Quantum computing has been theorized for many decades and has been actively pursued for at least 15 years. The largest quantum computer publicized to date has 72 qubits. Though that leaves plenty of room to grow, IBM has unveiled the first commercial quantum computer, which certainly must still require a lot development, and will not be available for consumers any time soon. Meanwhile, in Asia, Chinese researchers have established quantum communication through satellites between cities separated by 1200 km.
Those demonstrations show that quantum computing comes with significant and wide ranging potential applications. However, considerable hurdles remain to be overcome before this technology can be widely adapted. For starters, the number of qubits is a simple measure of potential computing power, but it doesn’t address whether the qubits are high quality or that they can be kept entangled or even in coherence. Decoherence is a big issue. The record for cohering qubits at room temperature is 39 minutes. Most quantum computing facilities go to great lengths to chill their systems and keep them under vacuums in order to maintain qubit stability in working environments.
In comparisons with traditional supercomputers, quantum computers have been proven to be potentially faster, but this speed has yet to be realized in practice. It is not known yet if the technological hurdles can be overcome. There is plenty of research money flowing into this field to find out if quantum computing can be fast and feasible. In fact, countries and companies are rushing into this field in the case that reality lives up to hype so that they don’t get left behind.
In short, quantum computing might revolutionize human society and artificial intelligence, but it has yet to be demonstrated to be practical. With the resources flowing into quantum computing research, we should know whether this technology will have practical applications within the next few years.