Ospelkaus, Christian
Tuesday March 26, 2013
Time: 14:00
Place: ETH Science City, HPF G 6
Host: Jonathan Home
Microwave quantum logic and a CPT test with single (anti-)protons
Christian Ospelkaus
Institut für Quantenoptik, Leibniz Universität Hannover
Most current schemes for multi-qubit quantum logic with trapped ions use focused laser beams for coherent operations. We discuss a scheme for logic gates with trapped-ion qubits based on microwave near-fields instead for coherent operations rather than laser beams. This could benefit integration, scalability, and fidelities. In our experiments, we have demonstrated both an entangling multi-qubit gate, as well as single-qubit gates with 2*10-5 error per computational gate, significantly below estimates for fault-tolerance error thresholds. More recently, we have been able to show how microwawe near-field gradients can also be used for individual addressing of ion qubits. We discuss individual-addressing methods and experimental fidelities, as well as perspectives for using the near-field approach for quantum simulation.
These same methods can also be used in a proposed experimental test of CPT invariance based on a comparison between the proton's and antiproton's magnetic moment [Heinzen and Wineland, PRA 42, 2977 (1990); Wineland et al., J. Res. NIST 103, 259 (1998)]. Rather than the more commonly used magnetic bottles and the continuous Stern-Gerlach effect, this method uses quantum logic spectroscopy for readout of a single (anti-)proton's spin state. This can enable rapid, single-shot spin readout as well as precise motional-state control, which will be key in pushing these experiments to physically interesting accuracies. We discuss an experimental setup which is currently under construction in Hannover and Braunschweig to implement this quantum logic detection scheme.
Work at NIST has been supported by IARPA, DARPA, NSA, ONR, and the NIST Quantum Information Program. Work at Hannover and Braunschweig is supported by the cluster of excellence QUEST, Leibniz Universität Hannover and PTB, Braunschweig.