Broadband Tunable Phase Shifter For Microwaves

Abstract

We implement a broadly tunable phase shifter for microwaves based on superconducting quantum interference devices (SQUIDs) and study it both experimentally and theoretically. At different frequencies, a unit transmission coefficient, |S 21 | = 1, can be theoretically achieved along a curve where the phase shift is controllable by magnetic flux. The fabricated device consists of three equidistant SQUIDs interrupting a transmission line. We model each SQUID embedded at different positions along the transmission line with two parameters, capacitance and inductance, the values of which we extract from the experiments. In our experiments, the tunability of the phase shift varies from from 0.07 × π to 0.14 × π radians along the full-transmission curve with the input frequency ranging from 6.00 to 6.28 GHz. The reported measurements are in good agreement with simulations, which is promising for future design work of phase shifters for different applications.

Bi‐Frequency Illumination: A Quantum‐Enhanced Protocol

“…This information can be related to the electromagnetic response of a reflective object to changes in frequency, and, consequently, the protocol can be applied to a wide spectrum of situations. Although the results are general, we suggest two applications within quantum microwave technology: radar physics, motivated by the atmospheric transparency window in the microwaves regime, together with the naturally noisy character of open-air; [71,98,[100][101][102][103] and quantum-enhanced microwave medical contrast-imaging of low penetration depth tissues, motivated not only by the non-ionizing nature of these frequencies, but also because resorting to methods that increase the precision and/or resolution without increasing the intensity of radiation is crucial in order not to heat the sample.…”

Bi-frequency illumination: a quantum-enhanced protocol

“…Such measurement can be used to extract information about the electromagnetic response of a reflective object to changes in frequency, and, consequently, it can be applied to a wide spectrum of situations. It is important to stress that although our results are general and platform-independent, the atmospheric transparency window in the microwaves regime, together with the naturally noisy character of open-air, makes applications in quantum microwaves our first choice [38,48,[50][51][52][53]. Namely, our results could find applications in radar physics, where the protocol could be understood as complementary to quantum illumination: quantum signals can enhance the precision of measurement without increasing the intensity, something very convenient when the emitter does not want to be detected.…”