Low-loss tunable metamaterials using superconducting circuits with Josephson junctions

Abstract

We report on experiments with superconducting metamaterials containing Josephson junctions. In these structures, split-ring resonators used in conventional metamaterials are replaced by superconducting loops that are interrupted by Josephson junctions, so called rf-SQUIDs. Like the split-ring resonators, these elements can be seen as LC-resonators that couple to the magnetic field. The advantage of superconducting thin-film metamaterials is that, due to the tunable intrinsic inductance of the Josephson junction, the resonance frequency of the rf-SQUID can be changed by applying an external dc magnetic field. We present experimental results that demonstrate the tunability of the resonance frequency of these devices.

From Josephson junction metamaterials to tunable pseudo-cavities

“…In particular, they make it possible to build qubits and few-level systems [29], or tunable linear and non-linear resonators [30,31,32], and they are also used to shape and enhance the qubit-resonator coupling [6]. In addition, junctions are at the heart of recent works which introduce quantum metamaterials for shaping the transport of microwave photons [17,18,19,20,12,16]. Working in the linear regime, the JJs act as local scatterers that can form band gaps and tailor the photon group velocity.…”

“…The building block of these studies is the scattering of photons through a qubit [9,10,11] or a Josephson junction (JJ) [12]. The reflection and transmission properties of these nonlinear scatterers have been probed in experiments with qubits [13,14,15] and SQUIDs [16]. More recently, arrangements of qubits or JJs have been suggested to tailor the propagation of light [17,18,19,20,12,21], conforming what is now called quantum metamaterials, the topic of this special issue.…”

Wide-band tuneability, nonlinear transmission, and dynamic multistability in SQUID metamaterials

“…The replacement of metallic SRRs with rf SQUIDs, which have no direct electrical conduct but instead they are coupled magnetically through their mutual inductances, has been suggested theoretically a few years ago [30,31]. Such SQUID metamaterials have been recently realized in the lab [18,19,32,24,25], that exhibit strong nonlinearities and wide-band tuneability with unusual magnetic properties due to macroscopic quantum effects. Nonlinearity and discreteness in SQUID metamaterials, along with low Ohmic losses (at least at microwave frequencies) may also lead in the generation of discrete breathers [33,34,35], i.e., time-periodic and spatially localized modes that change locally the magnetic response.…”

“…Superconductors, on the other hand, are intrinsically nonlinear materials, due to the extreme sensitivity of the superconducting state in external stimuli [7,8], which moreover exhibit significantly reduced Ohmic losses. They thus provide unique opportunities to the researchers in the field for the fabrication of superconducting metamaterials with highly controllable effective electromagnetic properties including wideband tuneability [9,10,11,12,13,14,15,16,17,18,19,20].…”

“…It consists of a superconducting ring interrupted by a Josephson junction (JJ) Josephson junction (JJ) [21], as shown schematically in figure 1(a). The SQUID is a strongly nonlinear resonator [22,23], that is tuneable over a wide frequency range by applying either a flux bias [18,24] or by varying the incoming rf power of an applied alternating field [24,25]. This superconducting device has found up to date numerous applications [26,27,28,29], and it is known to be the worlds most sensitive detector of magnetic signals.…”