This spring, "Ant-Man and the Wasp: Quantumania" premiered in movie theaters across the U.S. The movie depicts a "quantum realm" – a world among subatomic particles. While the ideas in the movie differ greatly from the current scientific consensus of the quantum world, applications of quantum mechanics aren't just fantasy; physicists around the globe are applying quantum principles to create powerful quantum computers that outperform conventional computers.

Quantum computers hold the promise of revolutionizing computing. Unlike conventional computers, they take advantage of quantum-mechanical effects that seem to fly in the face of how humans typically experience the world. Because quantum computers follow an entirely different set of rules than traditional computers, they can solve certain problems exponentially faster.

University of Arizona students have developed a computer game to make complex quantum computation concepts easier to grasp. The game challenges users to arrange puzzle pieces into a shape that models a quantum computing circuit. The game was designed to teach students, and even quantum researchers, an unconventional model of quantum computation.

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Ashlesha Patil –  a doctoral student in University of Arizona Wyant College of Optical Sciences and the university-housed, National Science Foundation-funded Center for Quantum Networks – presented the puzzle project at a virtual meeting of the American Physical Society on March 22. The project was done under the mentorship of Center for Quantum Networks director Saikat Guha, who is a professor in the Wyant College of Optical Sciences, and Don Towsley, a professor at the University of Massachusetts Amherst.

Patil relates the game to tangram, a puzzle game that was invented in China in the late 1700s. This game includes seven puzzle pieces, each a particular geometric shape and size. Even with just seven pieces, there are more than 1 billion possible ways the pieces can be arranged.

"Our game is much like tangram because the players are challenged to arrange colored blocks on a grid," Patil said. "The game isn't exactly 'real' quantum computation, but rather an educational tool to teach students – and even scientists – an unconventional, measurement-based way of mapping quantum circuits."

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Patil and her teammate Yosef Jacobson, an undergraduate double majoring in computer science and game design and development, have almost wrapped up the development phase of the computer game. They are awaiting minor cosmetic changes before the game will be tested by a broad range of users. The current version is designed to educate students in middle school and high school, and Patil believes that the game could help prepare the upcoming generation to build and optimize quantum computers.

"The quantum information industry is growing and needs a workforce that is trained in quantum theory," Patil said, adding that quantum computers have the potential to model atoms and molecules in ways that are immensely useful for several applications, including new types of drugs, batteries, fertilizers and energy sources.

"Even if a player doesn't end up in a career related to quantum computation, we hope this game might inspire them to go into a STEM-related field," Patil said. "Our hope is that this game could generate excitement about science, in general, with young students."

Drag and drop: Players model quantum circuits

Conventional computers rely on electrical charges to encode information – typically represented by ones and zeroes, which in turn encode bits. Quantum computers, on the other hand, use quantum bits, or "qubits," which can assume a state of both zero and one simultaneously until the state is actually measured, a property called superposition. Because of this, groups of qubits can represent vastly more combinations than classic computer bits.

The states of bits and qubits can be changed by hardware called "gates." All digital devices use gates in their computer circuits.

"A classical computer uses gates, such as the NOT gate, which converts a zero bit into a one bit," Patil explained. "Similarly, there are quantum gates that act on single or multiple qubits simultaneously to change their state, which are represented by the puzzle pieces in our game."

Whether players are aware of it or not, they are modeling a quantum circuit as they drag and drop colored blocks – quantum gates – onto the game grid, with each horizontal line on the grid representing a qubit. Each round, a random quantum circuit is generated, and the user is prompted to arrange the gates for that quantum circuit while following specific rules. These rules are governed by a measurement-based model of quantum computation, abbreviated as MBQC.

"One way to implement this game is to let students have fun with the game first, then explain what they actually accomplished later," Patil said. "In this way, even young students can gain a more intuitive understanding of the model without having to know all the technical details."

The goal of the game, which is played by one player at a time, is to cover the least possible amount of area when aligning the puzzle blocks or quantum gates. If the player successfully solves the circuit, they are given a score based on how "tightly" they were able to pack the blocks and therefore solve the puzzle. 

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The game is based off the MBQC model, which takes into account another quirk of the quantum world that is extremely difficult to reconcile with our everyday experience: entanglement.

"Entanglement is a quantum phenomenon in which particles are 'connected,' even across vast distances," Patil said. "This means that a certain physical property of the particles is completely correlated so that if you measure the physical property of one particle, you can determine the property of the other particle."

To perform computation using the MBQC model, researchers initially prepare multiple qubits that are already locked in an entangled state. They then work backward by using the measurements, or whether the qubit ends up as a zero or one, on the entangled qubits to implement gates.

"MBQC is not a very intuitive model because it differs greatly from the way we understand classical computers," Patil said. "Even scientists in the quantum research community are less familiar with it, and that's why we developed this game."

Conventionally, researchers focus on gates when depicting quantum computation in a different model called the circuit model. This method closely relates to classical computers.

"Our game takes the intuitive part of a classic circuit model – gates – and maps them into puzzle blocks that signify measurements in the MBQC model," Patil said. "This reduces some of the confusion that comes with understanding MBQC measurements, making the model easier to grasp."

Like the centuries-old tangram, the student-developed computer game holds numerous possibilities.

"An optimal mapping of a quantum circuit to measurement-based quantum computation is an open problem that has not been completely solved," Patil said. "We're still figuring out the best way to 'pack' the puzzle blocks the most efficient way for real quantum circuits. Especially when there are many qubits, things get complicated."

The game project was funded by an engineering workforce development fellowship that Patil received from the Center for Quantum Networks, or CQN. UArizona was awarded $26 million under the National Science Foundation's Engineering Research Center program in September 2020 to establish the center, which is also supported by the Department of Energy.

CQN is laying the technical foundations of the first U.S.-based quantum network that can distribute quantum information at high speeds, over long distances. Along with these technological goals, the center prioritizes community-based outreach to students, offering them opportunities in quantum research.  

"Our outreach focuses mostly on the lower income areas of Arizona where the students have never met scientists before," Patil said. "As you can imagine, the students get very excited to see the scientists from CQN."

Once the computer game is finished, Patil hopes it will be included in outreach efforts and eventually reach students in classrooms around the nation.