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Cryogenic surface electrode ion traps for quantum computation

Shannon Wang, Massachusetts Institute of Technology

(Session 5 : Friday from 5:00-7:00)

Abstract. Dense arrays of trapped ions provide one way of scaling up ion trap quantum information processing. However, miniaturization of ion traps is currently limited by sharply increasing motional state decoherence at sub-100μm ion-electrode distances. The ability to address individual ions and perform quantum operations in such dense, small ion traps is another important challenge. We present a cryogenic ion trap system using microfabricated traps, which addresses the heating and addressing issues. In these traps, a single trapped Sr+ ion is characterized using the temperature dependence between 10-100 K to elucidate the heating mechanism. At 6 K, heating rates are observed to be as low as two quanta per second with the ion located 100 μm above the surface; this heating rate is more than two orders of magnitude lower than the best results obtained in a comparable trap at room temperature. The cryogenic system enable novel use of superconductors as flux shields to stabilize the magnetic field, and the low heating rates enable high fidelity quantum operations. We performed coherent operations on the internal and motional state and found the classical fidelity of a Controlled-NOT gate to be 95%. We also performed some initial experiments on full process tomography of the CNOT gate. Finally, we have developed a scheme to create a local magnetic field gradient by integrating current sources onto a microfabricated surface-electrode trap, and obtained some initial experimental results on individual addressing of ions. The low heating rates and individual addressing in a cryogenic surface-electrode ion trap makes it a viable candidate system for realizing scalable quantum computation.