Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 99: Poster Session: Transport

TT 99.50: Poster

Donnerstag, 15. März 2018, 15:00–19:00, Poster B

Model Studies of High Fidelity Entangling Gates — •Joel Christin Pommerening and David DiVincenzo — JARA Institute for Quantum Information, RWTH Aachen University, 52056 Aachen, Germany

We study high-fidelity operations on two coupled superconducting qubits. We consider the cross-resonance gate, presenting a straightforward analytic derivation of its action based on the theory of Makhlin invariants.

Starting from an effective J coupling between the qubits, this derivation relies on a single rotating wave approximation to make the Hamiltonian time-independent in the frame that is rotating both qubits at the frequency of the cross-resonant drive. At that point no further frame or basis transformations are necessary, and the model can be solved exactly. A time evolution locally equivalent to a CNOT gate can then be found in multiple bases in the limit of small coupling strength J, and in one basis in particular for any J.

In practice the qubit basis is of course not arbitrary, but can be defined by the measurement basis or the basis in which single-qubit gates are applied. In this context we study how the (always-on) two-qubit coupling affects single-qubit measurements, and more specifically the measurement basis. In doing so we eventually seek to better understand the errors that arise from a possible mismatch between measurement and qubit basis.