I work for a quantum information research group at ICFO, a research centre in Castelldefels, near Barcelona, although we have many colleagues around the world.

In addition to promoting scientific and technological research, I think it is important to tell people about how the latest scientific advances can affect their lives.

In 2016, we coordinated an international project to conduct a quantum physics experiment with the collaboration of the public. More than 100,000 people took part in the Big Bell Test!

One of my favourite YouTube channels is one in which a young engineer explains how everyday objects work.

Just yesterday she explained how our cell phones contain lots of transistors and other parts made of semiconductors that are the basic building blocks of digital electronics. All this could not be done without understanding the quantum properties of semiconductor materials that are the basis of these parts.

I did not know I had quantum technology in my pocket! Yeah!

I am a physics teacher at a secondary school. I am concerned about people's lack of knowledge about scientific matters. There are more and more pseudo-scientific scams that use technical names and take advantage of misinformation and lack of critical spirit, which do nothing but take money from people. No, there is such thing as a quantum doctor! Science is not magic.

I am trying to get my students to understand scientific concepts and analyze with a critical attitude the information they receive in their daily life.

In some experiments, the result does not allow us to distinguish which path the particle has taken: it is as if it were traveling along two paths at once! What we can observe is the effect of the interference between the two paths.

If we block one path, we no longer see interference, even though the particle has gone through the open path. It is as if it knew what is happening on the other path without going along it.

Applications: detecting and/or observing objects without interacting.

New quantum technologies are emerging that promise to revolutionise the information and communication world: in order to maximise this potential, the European Union is planning to build quantum communications infrastructure, which would allow quantum devices to be connected and eventually form a quantum internet. This infrastructure will make use of the current fibre optic network for short- and medium-distance connections and combine satellites to cover longer distances. The most sensitive data, such as personal, financial and government information, as well as electricity grid, air traffic control and health system data, will thus be protected thanks to quantum physics.

Photo: Clouds of cold atoms in one of ICFO's laboratories.

In order to send an encrypted message, you must have a key to encrypt and decrypt the message. The problem is how to send the key from the sender to the receiver without it being intercepted.

Thanks to superposition and the effect of measurement on quantum systems, we can share keys securely and remotely.

Quantum key distribution systems can even detect the presence of spies.

Commercial encryption systems based on quantum physics already exist.

Quantum physics has enabled us to better understand the properties of many materials, such as semiconductors, but there are some we do not understand because the calculations we would have to perform to understand them are too complex, even for the most powerful computers.

As we wait for the arrival of quantum computers, we can start using simple quantum systems that we can precisely control in a lab, such as a cloud of cold atoms, which behave like the more complex systems we want to study. These are quantum simulators, which promise to help us understand materials that are interesting for their technological applications, such as superconductors.

When we measure a quantum system, we alter its properties: the system collapses and we observe a single, well-defined property. If we cannot avoid the effect of our presence as observers on the system, how can we really know anything for sure?

On various occasions, applications and techniques that have very widespread use and impact today were developed in a stage secondary to achieving the research's main objective. For example, the internet was created at an international particle physics research centre, CERN; satellite positioning systems (GPS, Galileo) owe their precision to the theory of general relativity.

Sometimes, research fields that, in principle, do not have obvious applications, generate useful technologies as side-effects. Should we invest in fundamental research for the potential benefits that would come from possible collateral applications? Or is the advancement of knowledge sufficient reason to put resources into research?

Their applications in all fields of human activity will radically change our lives, just as electricity and electronics once did. We must invest as much as we can in their development, to make them commercially viable as soon as possible. 

We should not be fooled by illusory promises. We have gone very far with traditional technologies and we still have a long way to go: we should keep the current investment in quantum technologies at the same level. Let scientists do their work and continue to research, focusing on maintaining and improving the technologies that we already have. 

Research into quantum physics and its applications is positive, but we currently have other far more important and pressing issues, such as hunger, poverty, wars and terrorism. Let us maintain research, but invest our money to find solutions to the major problems our society has today.  

Quantum technologies are very promising, but if they are to be effective, they require solid knowledge of their foundations. We should invest in fundamental research: a better understanding of the foundations of quantum physics will naturally lead to the development of its applications.