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U of Chicago achieves unheard-of qubit density from new, hybrid quantum design leveraging 2 types of qubits,

By IQT News posted 09 Mar 2022

(TomsHardware) A team of researchers with the University of Chicago have achieved unheard-of qubit density thanks to a new, hybrid quantum design. Leveraging two types of qubits, the researchers could pack 512 quantum computing units in the same array, establishing a new record in the process. However, not all of these qubits are equal; and that’s by design. The research could bring hybrid quantum computing designs to the forefront to enable more effective quantum scaling.
It turns out that pairing two different types of qubits in the same array allows for measurements and operations to be carried out without affecting coherence in the other. The University of Chicago researchers created a hybrid array with equal parts cesium and rubidium qubits – 256 each for 512 total – placed in an alternating pattern. Due to this deposition design, each atom is surrounded by atoms from the other element. Since each of these elements requires a specific laser wavelength forinteraction, this means that changing or reading the state of a cesium atom (or group of cesium atoms) can be done whilst minimizing interference with rubidium-based qubits, as they’re not sensitive to the same laser wavelengths (the reverse is also true).
“When you do these experiments with the single atoms, at some point, you lose the atoms,” said Hannes Bernien, lead researcher on the study. “And then you always have to re-initialize your system by first making a new, cold cloud of atoms and waiting for individual ones to get trapped by the lasers again. But because of this hybrid design, we can do experiments with these species separately. We can be doing an experiment with atoms of one element, while we refresh the other atoms, and then switch so we always have qubits available.”
The researchers’ design thus opens the door towards higher qubit uptime – one set of atoms can be used to compute while the other is being reloaded and fed with subsequent workloads. This is, in itself, an achievement, as this is the world’s first qubit array that can operate continuously, with a theoretical downtime of zero. The research also paves the way towards more versatile quantum computing scenarios.
It will take time before the research translates into actual products – if ever – but the door is now ajar for more significant qubit counts while maintaining ease of read-out.

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