Waveguide Bandgap Engineering with an Array of Superconducting Qubits

Abstract

In this work, we experimentally study a metamaterial made of eight superconducting transmon qubits with local frequency control coupled to the mode continuum of a superconducting waveguide. By consecutively tuning the qubits to a common resonance frequency we observe the formation of super-and subradiant states as well as the emergence of a polaritonic bandgap. Making use of the qubits strong intrinsic quantum nonlinearity we study the saturation of the collective modes with increasing photon number and electromagnetically induce a transparency window in the bandgap region of the ensemble, allowing to directly control the band structure of the array. The moderately scaled circuit of this work extends experiments with one and two qubits [1, 2] towards a fullblown quantum metamaterial, thus paving the way for large-scale applications in superconducting waveguide quantum electrodynamics.

Waveguide bandgap N-qubit array with a tunable transparency resonance

“…In Section III we consider the N -odd qubit chain where N −1 qubits have the same excitation frequency Ω, whereas the excitation frequency Ω 0 of a central qubit is different. In general, if we add new energy Ω 0 to the system it can give rise to new resonance, as was experimentally shown in [7]. However, we show that for our structure there exists inside the gap a frequency where the reflection amplitude equals exactly zero.…”

“…The multiple qubit system obtains an infinite range photon mediated effective interaction which can be tuned with the inter-qubit distance. Furthermore, this system exhibits collective excitations with lifetimes ranging from extremely sub-to superradiant relative to the radiative lifetime of the individual qubits [4,5,7,8].…”

Quantum chaos driven by long-range waveguide-mediated interactions

“…Introduction. Arrays of superconducting qubits or cold atoms coupled to a waveguide, have recently become a promising new platform for quantum optics [1][2][3][4][5][6][7]. They can be used for storing [8] and generating quantum light [7,[9][10][11], and even a future "quantum internet" [12].…”

“…Our findings apply to various two-particle systems and will be hopefully useful also for the many-body setups. Experimental verification could be done with already available arrays of tens of superconducting qubits [6,44] with the possibility to excite and probe every qubit separately [45].…”

Topology-Enhanced Nonreciprocal Scattering and Photon Absorption in a Waveguide

“…Implementation.-The waveguide QED with a topological atom array can be implemented in different experimental platforms, e.g., superconducting quantum circuits [94][95][96]. Recently, waveguide QED with multiple superconducting artificial atoms has made enormous progress in experiments [93,[97][98][99][100][101]. A topological array with tunable interactions of atoms has been implemented with superconducting quantum circuits [54].…”