I am a pharmacist and in my work it is essential for my scales to be precise to prepare prescription medicines. For this reason, I recalibrate them every year. When I did it in 2019, I was told that the definition of a kilogram in the International System of Units had changed. The definition of the unit of weight used worldwide is now based on a universal constant, the Planck constant, which plays a fundamental role in quantum physics.

A lot of people are concerned about knowing which interpretation of quantum physics is the right one and truly describes the world we live in. I think this issue is really irrelevant, since the success of quantum physics lies in predicting many phenomena that have been tested experimentally.

Ultimately, this is the only thing that is useful to us and that allows us to keep making progress!

I am an expert in cybersecurity. Nowadays, practically our whole life is connected to the internet: personal information, financial data, etc. In order to protect our privacy, we need to develop and improve the cryptographic methods we have.

I am worried that quantum computers will jeopardise this security, but it is a relief to know that quantum physics also provides us with tools to exchange information securely, regardless of how powerful computers are and will be.

The speed of a tennis ball is the result of the superposition of a horizontal and a vertical component.

With quantum particles, we can create even more surprising superpositions, such as an atom in an excited and unexcited state at the same time, or a particle that goes along two paths at once.

Applications: computing (greatly speeding up how long it takes to solve some problems); cryptography (allowing ultra-secure communications).

We cannot describe the properties of two entangled particles separately.

If we measure the polarisation of a photon (the plane of oscillation of a light wave), the polarisation of the entangled photon will also be instantly determined!

We can only entangle quantum particles, which we can use to teleport information, for example.

Applications: this is the basis for most of the new quantum technologies, such as computing and cryptography.

If everything is made up of quantum particles (atoms, etc.), how can the macroscopic world not have the same “strange” properties as quantum particles?

The correspondence principle states that classic behaviour is the statistical result of the random behaviour of a large number of quantum particles.

We do not yet know where the boundary between quantum and classical theory lies.

Quantum particles behave in a similar way to classical waves, so we could create technologies for material beams (atoms) analogous to those for light.

Examples: matter lasers, atomic interferometers, atomic lenses and mirrors, etc.

The advantage is that these devices would be very sensitive to variations in the gravitational field and inertial effects with applications in the manufacture of accelerometers (sensors that detect position changes, which are found in smartphones and tablets), for example.

We often feel that quantum physics is extremely difficult to understand and this frequently leads to misunderstandings. Is it really that way, compared with other disciplines such as astronomy and chemistry, or it is simply because the concepts are unintuitive? Why should we be more surprised by the random nature of quantum physics than the existence of gravity?

In the 1960s, most futuristic representations of the years around 2000 included flying cars. Now, more than 20 years later, our expectations concerning the future have changed considerably.

Does it make sense to listen to people who promise us that their field of study will bring us the technology of the future? Can we really make predictions about the future of science and technology?

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.