14 September 2015

Viewpoint: Wiring Up Superconducting Qubits

Viewpoint: Wiring Up Superconducting Qubits

As reported in the American Physical Society Journal Physics 8, 87 (2015):

Despite remarkable progress over the past few decades, it remains unclear what form quantum computers will eventually take. Different kinds of quantum bits, or qubits, exist today, but the ideal qubit has yet to emerge. The challenge is that a qubit must satisfy contradictory requirements: It must be isolated from its environment to preserve quantum coherence, but also retain enough coupling to the outside world to enable manipulation and measurement. One possible solution is to combine the advantages of several types of qubits in hybrid architectures.

Two independent groups have now demonstrated a new qubit scheme, consisting of two superconductors bridged by a nanowire, that could help researchers design quantum circuits with more flexibility. The teams, led by Leonardo DiCarlo at Delft University of Technology in the Netherlands [1] and Charles Marcus at the University of Copenhagen in Denmark [2], have demonstrated structures in which the nanowire replaces one of the basic elements of a superconducting qubit—the insulating barrier between two superconductors that forms a Josephson junction. The scheme enables the control of the junction properties by an applied electric field, which will lead to superconducting qubits that are easy to tune. The structure might also provide a way to combine the controllability of superconducting qubits with the long coherence times of solid-state spins or future topological qubits.

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