Saturday, July 09, 2022

Quantum Games -- Really!

[This is a transcript of the video embedded below. Some of the explanations may not make sense without the animations in the video.]

It’s difficult to explain quantum mechanics with words. We just talked about this the other day. The issue is, we simply don’t have the words to describe something that we don’t experience. But what if you could experience quantum effects. Not in the real world, but at least in a virtual world, in a computer game? Wait, there are games for quantum mechanics? Yes, there are, and better still, they are free. Where do you get these quantum games and how do they work? That’s what we’ll talk about today.

We’ll start with a game that’s called “Escape Quantum” which you can play in your browser.

“You find yourself in a place of chaos. Whether it’s a dream or an illusion escapes you as the shiny glint of a key catches your eye. A goal, a prize, an escape, whatever it means for you takes hold in your mind as your body pushes you forward, into the unknown.”

Alright. Let’s see.

Escape Quantum is an adventure puzzle game where you walk around and have to find keys and cards to unlock doors. The navigation works by keyboard and is pretty simple and straight forward. The main feature of the game is to introduce you to the properties of a measurement in quantum mechanics, that if you don’t watch an object, its wave-function can spread out and next time you look, it may be at a different place.

So sometimes you have to look away from something to make it change place. And if there’s something you don’t want to change place, you have to keep looking at it. At times this game can be a bit frustrating because much of it is dictated by random chance, but then that’s how it goes in quantum mechanics. Once you learn the principles the game can be completed quickly. Escape Quantum isn’t particularly difficult, but it’s both interesting and fun.

Another little game we tried is called quantum playground which also runs in your browser.

Yes, hello. What you do here is that you click on some of those shiny spheres to initialize the position of a quantum particle. You can initialize several of them together. Then you click the button down here which will solve the Schrödinger equation, with those boundary conditions, and you can see what happens to the initial distribution. You can then click somewhere to make a measurement, which will suddenly collapse the wave-function and the particle will be back in one place.

There isn’t much gameplay in this one, but it’s a nice and simple visualization of the spread of the wave-function and the measurement process. Didn’t really understand what this little bird thing is.

Somewhat more gameplay is going on in the next one which is called “Particle in a Box”.  This too runs in your browser but this time you control a character, that’s this little guy here, who can move side to side or jump up and down.

The game starts with a brief lesson about potential and kinetic energy in the classical world. You collect energy in terms of a lightning bolt and give it to a particle that’s rolling in a pit. This increases the energy of the particle and it escapes the pit. Then you can move on to the quantum world.

First you get a quick introduction. The quantum particle is trapped in a box, as the title of the game says. So it doesn’t have a definite position, but instead has a probability distribution that describes where it’s most likely to be if a measurement is made. Measurements happen spontaneously and if a measurement happens then one of these circles appears in a particular place.

You can then move on to the actual game which introduces you to the notion of energy levels. The particle starts at the lowest energy level. You have to collect photons, that’s those colorful things, with the right energy to move the particle from one energy level to the next. If you happen to run into a particle at a place where it’s being measured, that’s bad luck, and you have to start over. You can see here that when the particle changes to a higher energy level, then its probability distribution also changes. So you collect the photons until the particle’s in the highest energy level and then you can exit and go to the next room.

The controls of this one are little fiddly but they work reasonably well. This game isn’t going to test your puzzle-solving skills or reflexes, but does a good job in illustrating some key concepts in quantum mechanics: probability distributions, measurements, and energy levels.

The next one is called “Psi and Delta”. It was developed by the same team as “Particle in a Box” and works similarly, but this time you control a little robot that looks somewhat like BB8 from Star Wars. There’s no classical physics introduction in this one, you go straight to the quantum mechanics. Like the previous game, this one is based on two key features of quantum mechanics: that particles don’t have a definite position but a probability distribution, and that a measurement will “collapse” the wave-function and then the particle is in a particular place.

But in this game you have to do a little more. There’s an enemy robot, that’s this guy, which will try to get you, but to do so it will have to cross a series of platforms. If you press this lever, you make a measurement and the particle is suddenly in one place. If it’s in the same place as the enemy robot, the robot will take damage. If you damage it enough, it’ll explode and you get to the next level.

The levels increase in complexity, with platforms of different lengths and complicated probability distributions. Later in the game, you have to use lamps of specific frequencies to change the probability distribution into different shapes. Again, the controls can be a little fiddly, but this game has some charm. It requires a bit of good timing and puzzle solving skills too.

Next game we look at is called “Hello Quantum” and it’s a touchscreen game that you can play on your phone or tablet. You first have to download and install it, there’s no browser version for this one, but there’s one for android and one for ios. The idea here is that you have to control qubit states by applying quantum gates. The qubits are either on or off or something you don’t know. Quantum gates are the operations that a quantum computer computes with. They basically move around entanglement. In this game, you get an initial state, and a target state that you have to reach by applying the gates.

The game tells you the minimal number of moves by which you can solve the puzzle, and encourages you to try to find this optimal solution. You’re basically learning how to engineer a particular quantum state and how a quantum computer actually computes.

The app is professionally designed and works extremely well. The game comes with detailed descriptions of the gates and the physical processes behind them, but you can play it without any knowledge of qubits, or any understanding of what the game is trying to represent, just by taking note of the patterns and how the different gates move the black and white circles around. So this works well as a puzzle game whether or not you want to dig deep into the physics.

This brings us to the last game in our little review which is called the Quantum FlyTrap. This is again a game that you can play in your browser and it’s essentially a quantum optics simulator. This red triangle is your laser source, and the green venus flytraps are the detectors. You’re supposed to get the photons from the laser to the detectors, with certain additional requirements, for example you have to get a certain fraction of the photons to each detector.

You do this by dragging different items around and rotating them, like the mirrors and beam splitters and non-linear crystals and so on. In later levels you have to arrange mirrors to get the photons through a maze without triggering any bombs or mines.

A downside of this game is that the instructions aren’t particularly good. It isn’t always clear what the goal is in each level, until you fail and you get some information about what you were supposed to do in the first place. That said, the levels are fun puzzles with a unique visual style. I’ve found this to be a quite remarkable simulator. You can even use it to click together your own experiment.  

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