In the world of computing, information is traditionally stored using binary encoding, represented by ones and zeros. However, in our everyday lives, we use ten digits to represent numbers. For instance, in binary, the number 9 is written as 1001, requiring three extra digits to express the same value.
While quantum computers are rooted in the binary paradigm, the physical systems that encode their quantum bits (qubit) have the potential to encode quantum digits (qudits) as well. Recently, a team led by Martin Ringbauer at the Department of Experimental Physics at the University of Innsbruck demonstrated this possibility. According to experimental physicist Pavel Hrmo at ETH Zurich, the challenge for qudit-based quantum computers has been efficiently creating entanglement between the high-dimensional information carriers.
In a study published in the journal Nature Communications, the University of Innsbruck team reports on their breakthrough in fully entangling two qudits with unprecedented performance. This development paves the way for more efficient and powerful quantum computers.
Thinking like a quantum computer
Let’s consider the example of multiplying 9 by 9. While humans can calculate this as 9 x 9 = 81 in a single step, a classical computer or calculator has to perform many binary multiplication steps, such as 1001 x 1001, before displaying 81 on the screen. Classically, we can afford to do this, but in the quantum world, where computations are highly sensitive to noise and external disturbances, we need to reduce the number of operations needed to maximize the potential of quantum computers.
Quantum entanglement is crucial for any calculation on a quantum computer. It is one of the unique quantum features that allows quantum computers to outperform classical computers in certain tasks. However, leveraging this potential requires the generation of robust and accurate higher-dimensional entanglement.
The natural language of quantum systems
The researchers at the University of Innsbruck have successfully fully entangled two qudits, each encoded in up to 5 states of individual Calcium ions. This breakthrough provides theoretical and experimental physicists with a new tool to go beyond binary information processing, potentially leading to faster and more robust quantum computers.
Martin Ringbauer explains, “Quantum systems have many available states that can be utilized for quantum computing, rather than being limited to working with qubits.” This more natural language of quantum computing can benefit a range of challenging problems in fields like chemistry, physics, and optimization.
The research received financial support from various organizations, including the Austrian Science Fund FWF, the Austrian Research Promotion Agency FFG, the European Research Council ERC, the European Union, and the Federation of Austrian Industries Tyrol.