Interqubit coupling mediated by a high-excitation-energy quantum object

Interqubit coupling mediated by a high-excitation-energy quantum object

Ashhab, S.
Niskanen, A.O.
Harrabi, K.
Nakamura, Y.
Picot, T.
De Groot, P.C.
Harmans, C.J.P.M.
Mooij, J.E.
Nori, F.

Applied Sciences

Kavli Institute of Nanoscience

2008-01-17

We consider a system composed of two qubits and a high excitation energy quantum object used to mediate coupling between the qubits. We treat the entire system quantum mechanically and analyze the properties of the eigenvalues and eigenstates of the total Hamiltonian. After reproducing well known results concerning the leading term in the mediated coupling, we obtain an expression for the residual coupling between the qubits in the off state. We also analyze the entanglement between the three objects, i.e., the two qubits and the coupler, in the eigenstates of the total Hamiltonian. Although we focus on the application of our results to the recently realized parametric-coupling scheme with two qubits, we also discuss extensions of our results to harmonicoscillator couplers, couplers that are near resonance with the qubits and multiqubit systems. In particular, we find that certain errors that are absent for a two-qubit system arise when dealing with multiqubit systems.

eigenvalues and eigenfunctions
harmonic oscillators
quantum computing
quantum entanglement

http://resolver.tudelft.nl/uuid:a9510c5b-d77c-440d-8f70-f1f368f4ea60

American Physical Society

0163-1829

Physical Review B, 77 (1), 2008

Institutional Repository

journal article

(c) The Author(s) ; American Physical Society