First 32-qubit trapped-ion quantum register at cryogenic temperatures

For the first time, researchers from Duke University and the University of Maryland have designed a fully connected 32-qubit trapped-ion quantum computer register operating at cryogenic temperatures. The new system represents an important step toward developing practical quantum computers.

Trapped-ion quantum computers cool ions to extremely low temperatures, which allows them to be suspended in an electromagnetic field in an ultra-high vacuum and then manipulated with precise lasers to form qubits.

Thus far, achieving high computational performance in large-scale ion trap systems has been hampered by the collisions with background molecules disrupting the ion chain, instability of the laser beams driving the logic gates seen by the ion, and electric field noise from the trapping electrodes agitating the ion’s motion often used to create entanglement.

The team addressed these challenges by incorporating dramatically new approaches. The ions are trapped in a localized ultra-high vacuum enclosure inside a closed-cycle cryostat cooled to 4K temperatures, with minimal vibrations. This arrangement eliminates the disturbance of the qubit chain arising from collisions with residual molecules from the environment, and strongly suppresses the anomalous heating from the trap surface.

To achieve clean laser beam profiles and minimize errors, the researchers used a photonic crystal fiber to connect various parts of the Raman optical system that drives qubit gates—the building blocks of quantum circuits. The laser beams are then delivered to the system in single-mode optical fibers. (

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