Position-dependent excitation of transmon qubits embedded in a 3D waveguide*

By embedding superconducting qubits into a microwave rectangular waveguide, it is possible to exploit the combination of short-range direct qubit interactions and long-range waveguide mediated interactions to model a wide variety of Hamiltonians [1]. This unique platform has great potential for quantum simulation, however the intrinsic dispersion of these waveguide and its potential impacts on the qubits has yet to be fully experimentally studied. Recently it has been shown [2] that it is possible to generate self-focusing pulses thanks to this non-linear dispersion relation which can theoretically be used to selectively control a qubit.

We experimentally demonstrate the control of transmon qubits depending on their position inside such a rectangular waveguide. Moreover, we discuss the experimental advantages and limitations coming from the use of such waveguides with broadband pulses required for the focusing effect to occur.

[1] Zanner, Maximilan et.al. “Coherent control of a multi-qubit dark state in waveguide quantum electrodynamics” Nature Physics 18, 538 (2022)

[2] Casulleras, Silvia, et al. "Remote individual addressing of quantum emitters with chirped pulses." Phys Rev Let (2021)