We all learned from early on that computers work with zeros and ones, also known as binary information. This approach has been so successful that computers now power everything from coffee machines to self-driving cars and it’s hard to imagine a life without them.
Building on this success, today’s quantum computers are also designed with binary information processing in mind. “The building blocks of quantum computers, however, are more than zeros and ones”, explains Martin Ringbauer, an experimental physicist from Innsbruck, Austria. “Restricting them to binary systems prevents these tools from living up to their true potential.”
The team led by Thomas Monz of the Department of Experimental Physics at the University of Innsbruck, has now succeeded in developing a quantum computer that can perform arbitrary calculations with the so-called quantum digits (qudits)thus unlocking more computational power with fewer quantum particles.
Quantum systems are different
Although storing information in zeros and ones is not the most efficient way to do calculations, it is the simplest way. Simple also usually means reliable and robust to errors and so binary information became the unchallenged standard for classical computers.
In the quantum world, the situation is different. In the Innsbruck quantum computer, for example, information is stored in individual trapped Calcium atoms. Each of these atoms naturally has eight different states, of which usually only two are used to store information. In fact, almost all existing quantum computers have access to more quantum states than they use to compute.
A natural approach for hardware and software
Physicists from Innsbruck have now developed a quantum computer that can use the full potential of these atoms, by computing with qudits. Contrary to the classical case, the use of multiple states does not make the computer less reliable. “Quantum systems naturally have more than two states and we have shown that we can control them equally well”, says Thomas Monz.
On the other hand, many of the tasks that require quantum computers, such as problems in physics, chemistry, or material science, are also naturally expressed in the qudit language. Rewriting this for qubits would often make them too complex for today’s quantum computers. “Working with more than zeros and ones is very natural, not only for the quantum computer but also for its applications, which allows us to unlock the true potential of quantum systems”, explains Martin Ringbauer.
Publication: A universal qudit quantum processor with trapped ions. Martin Ringbauer, Michael Meth, Lukas Postler, Roman Stricker, Rainer Blatt, Philipp Schindler, Thomas Monz. Nature Physics 2022. DOI:10.1038/s41567-022-01658-0 [arXiv:2109.06903]
A universal qudit quantum processor with trapped ions
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