The understanding and application of quantum mechanics have already given us many technologies that we use every day, from transistors and LEDs to lasers and GPS. Today, we are entering a new quantum revolution, with the promise of quantum computers, secure quantum communication, ultra-sensitive quantum sensors, and extremely precise optical atomic clocks.

In this lecture, I will explore what quantum technologies are and how our research group has joined the global race to develop them. I will take you on a short tour of the experiments we are doing in our Quantum Technologies group, focusing on three areas: quantum simulators, quantum sensors, and quantum memories. For our quantum simulators, we use cold rubidium atoms trapped inside a high-finesse optical cavity. Our quantum sensor is an optical atomic clock based on cold strontium atoms, while for quantum memories we work with warm rubidium vapour.

I will give you a taste of what experimental quantum physics looks like in our laboratory, where lasers are used to create, control, and manipulate quantum systems.

And if you want to see what all of this really looks like, you will have to come and visit us at the CALT Department of the Institute of Physics in Zagreb!

In this talk I want to convey how quickly we reach open problems with no ready answers, using only a few simple ingredients on the scale of a tabletop (or a couple of them). Drawing on examples from complex systems, fluid dynamics and nonlinear physics, I will describe an approach to physics on the human scale — one that combines experiment and model building, and remains visual and driven by intuition.

I will argue that we don't need to go far to find hard problems, discuss how to recognise them, and show that they readily lead to high quality research.

IPT problems often resemble real research questions in just this way, and with the right approach the skills and experience gained from the tournament can bring you quickly into active research.

Several cultures use water as a musical instrument, creating a variety of sounds depending on how the surface of the water is stroked. We investigated three such stroke techniques – the slap, the plunge and the plow.

First we slapped the water, and found out the hand is an approximated Helmholtz resonator. Second, we plunged our "hand" into the water, we analysed the cavity collapse dynamics and approximated the resonant frequency of the cavity. Last but not least, we plowed through the water, and found out that the associated sound is not created by splashes of water, but by bubbles, driven to collapse by turbulence!

Using our discoveries, we can create music! We used a variety of experimental setups, including a seesaw-like system for the slap, and a moving platform with our 3D-printed hand approximation mounted upon it for the plow.

Foams represent complex soft-state systems which embody many interesting diffusion, breakage and coalescence phenomena. In our work, we have studied the properties of wet and dry foams in everyday beverages such as fizzy drinks and beer.

We theoretically modelled bubble evolution with numerical models combining continuous bubble growth with stochastic bubble breakage.

Using our theoretical model, we were able to predict the functional dependence of the foam height on time, which we confirmed using a repeatable experimental setup. The results show an exponential decay for dry foam systems, such as fizzy drink foam, and a power-law decay for wet foams, as in the case of beer foams.

Figure skating jumps require a precise combination of translational and rotational motion.

A simple and accessible method for the automated analysis of biomechanical jump parameters using inertial sensors integrated into a smartphone is presented. Data from six competitive female figure skaters were collected during on-ice and off-ice training and used to analyse flight time, estimate jump height and maximum angular velocity for Double Axel, Triple Salchow, and Triple Toe Loop jumps.

Results showed differences between on-ice and off-ice execution, with maximum angular velocity consistently higher on ice. Developed method demonstrates the potential of smartphone sensors for accessible monitoring of figure skating performance under real training conditions.

Problems in the IPT, and similar competitions such as IYNT and IYPT, surprisingly often ask for a solution to an engineering problem presented as a physics problem. IPT 2026 Problem 5, the "Ping-Pong Balls Cannon", is a clear example. It asks for a device that launches ping-pong balls as far as possible; meaning there is no single phenomenon to explain, but rather a design space to explore, almost from first principles. This makes it a different challenge from the traditional physics problems, but one that is especially rewarding for a physics student.

This talk presents the solution to the cannon as a case study, while also using it to outline a general workflow for such problems: showing how physical intuition can drive design decisions, and where physics has to be supplemented by empirical and engineering judgement.

A string telephone is something most are familiar with and have played with as a child. Some even schemed to build one stretching all the way to a friend’s house or even a network to multiple houses.

In this presentation those plans are revisited by analysing the acoustic properties of a string telephone from the perspective of signal transmission with focus on wave dampening in the string and the transition from string to cup.

The goal is to not only maximize the range, but also to modify the telephone to have a group call.

A shallow water tank mechanically excited by a motor features some of the basic ingredients of a laser (i.e., a cavity and an amplifier). To what extent can this simple analogy capture more complex aspects of laser physics?

The presentation will demonstrate how to create a resonant cavity in a water tank, discuss its limitations, and explore other fascinating analogies between water waves and advanced phenomena in optics and laser physics.

You have probably made and played with string telephones during childhood without giving it that much thought. Taking a closer look into these simple devices reveals interesting physics and important parameters regarding the phone's structure and setup. This talk will show how altering certain parameters influences the string phone's performance, pushing it to its limits!

The Maxwell's Demon appears to violate the second law of thermodynamics which would have drastic implications. Using the Szilard's engine as an example we discover its difficulties and beauties.