Fundamental Science: Quantum winter is on the way


After inflated promises from researchers and unrealistic expectations from the media and industry, artificial intelligence went through cycles – called “AI winter” – of little investment and interest. Many believe that similar moments are about to happen with revolutionary, if still embryonic, quantum technologies.

Elaborated over the first decades of the 20th century, quantum theory brought to light a new physical paradigm, in which probabilities and uncertainties became the rule. Its conceptual difficulties are already legendary and offer fertile ground for the most varied pseudosciences. But despite the numerous debates – still ongoing – about its foundations, quantum physics has passed all experimental tests, being the most accurate theory ever created, essential for understanding the chemical and electronic properties of atoms and molecules, the interaction between light and matter, of varied astrophysical and cosmological effects and, more recently, even biological phenomena.

Quantum, unparalleled in showing the synergy between science and technology, is at the heart of modern life: in the transistors without which our computers and smartphones would not exist, in the laser and nuclear magnetic resonance that save lives every day. It is estimated that at least a third of all wealth generated today is the result of this first quantum revolution.

We are currently witnessing the second quantum revolution, which, making use of effects such as superposition and entanglement – ​​the latter dubbed by Einstein the “ghostly effect at a distance” – has made previously unthinkable tasks possible. Today, not only the devices, but the logic and algorithms through which information is processed have also become quantum. Some examples are quantum cryptography, which guarantees information security (only in danger if a hacker breaks the very rules of nature), and quantum computing, with applications ranging from the optimization of financial systems and logistical problems to the simulation of new drugs and materials.

With such a huge list of possibilities, it is not surprising that governments and large companies are betting big on the sector. If in 2015 the amount invested, in global terms, was just over 1 billion dollars, today it has already surpassed the barrier of 30 billion dollars. In five years, it is estimated that the market value of these technologies will exceed 50 billion dollars.

Despite all the hype, however, materializing such quantum technologies outside the laboratory, in large-scale applications of real practical interest, is still an enormous challenge. To make these admirable quantum machines operational, we need to build qubits, the quantum bits, make them interact, and above all protect them from interference from the external world, since quantum effects are extremely sensitive and disappear quickly. In quantum computing, this implies the use of complex error correction codes, and although IBM recently launched its new quantum computer surpassing the 400 qubit barrier, it is estimated that in relevant commercial applications at least 100,000 are needed. qubits.

Such a scenario has motivated pessimism in some sectors, who claim that the hype bubble is about to burst, bringing with it a lasting quantum winter that would irremediably affect not only technologies but also basic research in quantum physics. In fact, IonQ, one of the leading quantum hardware companies in the market, has lost 75% of its value in just one year.

Although a large-scale quantum computer is a dream for a few years (or decades…), the truth is that other quantum technologies are already a reality. Quantum cryptography was used as early as 2007 to secure part of the electoral process in Geneva, Switzerland. Quantum sensors also already exist and their applications in medicine, navigation, geophysical prospecting and interferometry are starting to become palpable. A quantum computer, albeit rudimentary, was recently used to simulate some properties of a wormhole, a kind of tunnel in space-time theorized by Einstein and whose real existence still remains unknown.

Winters are common to any new technology and should not be taken as proof of failure. After two cold cycles that together lasted almost 15 years, artificial intelligence established itself with one of the most disruptive technologies of the 21st century: autonomous cars, facial identification, virtual assistants, discovery of new drugs, etc.

It is quite likely that some version of quantum winter is on the way. But nothing a good sweater, a good dose of skepticism about quantum hype and quantum evangelists (yes, apparently that’s a profession now!) and a piping hot coffee don’t come in handy.


Rafael Chaves is a physicist, researcher at the International Institute of Physics at UFRN and author of the popular book “Uncerteza Quantica”.

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