Editor's Summary

27 September 2007

Catching the quantum bus


Microfabricated superconducting circuit elements can harness the power of quantum behaviour for information processing. Unlike classical information bits, quantum information bits (qubits) can form superpositions or mixture states of ON and OFF, offering a faster, natural form of parallel processing. Previously, direct qubit–qubit coupling has been achieved for up to four qubits, but now two independent groups demonstrate the next crucial step: communication and exchange of quantum information between two superconducting qubits via a quantum bus, in the form of a resonant cavity formed by a superconducting transmission line a few millimetres long. Using this microwave cavity it is possible to store, transfer and exchange quantum information between two quantum bits. It can also perform multiplexed qubit readout. This basic architecture lends itself to expansion, offering the possibility for the coherent interaction of many superconducting qubits. The cover illustrates a zig-zag-shaped resonant cavity or quantum bus linking two superconducting phase qubits.

News and ViewsQuantum physics: Qubits ride the photon bus

Quantum mechanics using whole electrical circuits might seem a far-fetched idea. But make the circuits superconducting, and they can be used to send and collect single photons, rather like atoms do — only better.

Antti O. Niskanen & Yasunobu Nakamura

doi:10.1038/449415a

LetterCoherent quantum state storage and transfer between two phase qubits via a resonant cavity

Mika A. Sillanpää, Jae I. Park & Raymond W. Simmonds

doi:10.1038/nature06124

LetterCoupling superconducting qubits via a cavity bus

J. Majer, J. M. Chow, J. M. Gambetta, Jens Koch, B. R. Johnson, J. A. Schreier, L. Frunzio, D. I. Schuster, A. A. Houck, A. Wallraff, A. Blais, M. H. Devoret, S. M. Girvin & R. J. Schoelkopf

doi:10.1038/nature06184