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Coupling of trapped ions via normal metal and superconductor transmission lines

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A step closer to quantum computers

Quantum computers are likely, one day, to boost our computing power and speed. One of the most promising paths is to use trapped ions to process information at the quantum level.

Digital Economy

Quantum computers, which employ quantum mechanical phenomena to process data, hold the potential to deliver a giant leap in computing power and speed, but the field is still in its infancy. One of the most promising candidates for the development of a quantum computer is the use of trapped ions, i.e. charged atomic particles which can be confined and suspended in free space using electromagnetic fields. Qubits – or units of quantum information – are stored in stable electronic states on each ion, and quantum information can be processed and transferred through the collective quantised motion of the ions in the trap. The EU-funded QOSC2007 project aimed to develop novel approaches to coupling trapped ions and transferring quantum information between them. The project worked to develop a solid-state quantum bus for trapped ions which would be capable of coupling the motional states of distant trapped ions. This route is of great technological and fundamental importance, and carries the potential to extend the scope of ion trap quantum computation. Current ion trap miniaturisation technology is limited by two major constraints: excessive electric field noise originating from trap electrodes, and the electrostatic charging of the traps. One way of reducing electronic noise is to operate the trap at cryogenic temperatures. QOSC2007 used a single trapped ion – both as an extremely sensitive noise sensor and as a movable electrostatic field sensor – to address these two challenges. The team established a possible connection between electric field noise and surface contamination of trap electrodes, which raises the possibility of using surface cleaning and characterisation tools, combining the standard atomic physicist's toolbox with that of the surface scientist, to resolve the problem. The researchers involved in QOSC2007 also developed an ion-trap fabrication process which decreases the size of ion traps, thereby boosting their speed, and assembles them in 'clean room' environments.

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