The Promise of the Quantum Computer
How does it work and how far away is it?
April 3, 2019, Bruno Jacobson
Quantum computers, fundamentally different from your typical computer or supercomputer, hold great promise. In theory, they would help solve equations, problems, and create simulations that are beyond the reach of even the most powerful supercomputer. For that reason, a lot of people are getting excited about them.
The Promise of the Quantum Computer
While quantum computing seems like the stuff of the future, the idea isn't new.
In 1980, Russian mathematician Yurin Manin first proposed the idea of a quantum computer. A year later, Richard Feynman, the American physicist and Nobel Prize winner, suggested that normal computers are limited in their abilities to simulate the evolution of quantum systems. Among his many achievements, he then proposed a basic model for a quantum computer that would be able to do this.
As years passed, figures such as Paul Benioff, David Deutsch, Peter Shor, and others, would go on to fine-tune the concept and provide algorithms capable of carrying it out. Since then, companies like IBM, Google, Intel, and Microsoft have jumped on the bandwagon, putting together "quantum teams" and building the hardware.
In 2017, 241 million US dollars went into startups working on quantum software or hardware, 3 times more than the year before. If anything, this is evidence that confidence in a breakthrough is increasing.
Nevertheless, most of the efforts going into quantum computing are still quite theoretical, despite the significant advances over the past few decades. First, a brief overview of how they work.
Classical computer bits are made of 0s and 1s. These strings of binary digits make all that you see (or hear) on your computers or mobile devices, from videos to photos to Facebook posts. These bits can only be 1s or 0s. However, in quantum mechanics, when you get to the very, very small, at the quantum level, particles can be in more than one state at a time (until they are measured). Whether they are 1s or 0s is a probabilistic matter, not a deterministic one. This phenomenon is called superposition. You might be a little familiar with this if you've heard of Schrödinger's cat.
Quantum computers use quantum bits. This means they can be in multiple states at once. These bits, called "qubits," are of a different nature altogether. Because they are in multiple states at the same time, they can calculate an enormous number of outcomes at once, allowing for a vastly greater probabilistic computation.
Of course, quantum computers aren't the answer to everything. As shown, they are particularly well-suited for certain types of tasks. For instance, they would very good at modelling chemical reactions, something even today's best computers can't do very well. This has gotten some scientists excited about the prospects of these quantum simulations to design entirely new molecules that could result in new medicines - or to improve the efficiency of creating artificial compounds such as ammonia, vital in many ways to us.
Using quantum simulations to understand things better at the molecular level brings other benefits, too. According to MIT Technology Review, it could help us also find new ways to improve the performance of electric-vehicle batteries, or more practical superconductors.
Recently, TechCrunch reported about a paper published in Science, where its authors show that even a basic quantum computer could outperform a classical computer in solving a variation of the Bernstein-Vazirani problem. This is an encouraging sign of the potential of quantum computers which have, nonetheless, faced some difficulties in becoming fully developed.
One of the main problems with quantum bits - qubits - is that they are prone to quickly experience decoherence. We mentioned that qubits exhibit the property of superposition. When there is noise in the environment, such as temperature changes, vibration, and almost anything else really, they are quick to fall out of that state of superposition. That's decoherence: their quantum state turns into a classical state.
According to the Technology Review, while a lot of effort has gone into protecting qubits from the external environment in order to avoid decoherence, it still remains a difficult task. It is estimated that one would need between 1,000 to 100,000 qubits in the hopes that one would remain "logical." At the moment, the maximum we have been able to pack into a quantum computer is 128 qubits.
Some even go further, claiming that such computers are beyond our reach and that building a useful one is impossible. According to physicist Mikhail Dyakonov, a useful quantum computer "needs to process a set of continuous parameters that is larger than the number of subatomic particles in the observable universe." One of the many issues, according to him, that makes quantum computers seem more like a fad of the past than a promise of the future.
With all of this, it is hard to say exactly how far we will get with quantum computers. We have undoubtedly seen some progress, even to the point where it has been able to solve a problem that a classical computer could not. However, it would seem like we are still at the very early stages of what we might call a revolution in computing.
Time will tell.
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