Nonlinear quantum optics with Josephson meta-materials
Arpit Ranadive
Metamaterials are artificially designed materials to exhibit properties not available in natural materials by engineering the constituting elements at sub-wavelength scales, enabling unique interactions of matter with electromagnetic waves or coupling modes of electromagnetic waves. Examples of such novel optics phenomenons include negative index of refraction, cloaking, and super-resolution imaging. The study of superconducting metamaterials operating in the microwave frequency domain has recently generated significant interest in the framework of quantum technologies due to a wide range of direct applications, e.g., exploration of novel quantum optics phenomena, non-destructive quantum sensing, quantum-limited amplification, quantum information processing, and quantum illumination. In contrast to their normal metal and semiconducting counterparts, superconducting metamaterials offer some unique advantages. The most relevant of these for Josephson junction based metamaterials are low losses, flux quantization, and Josephson effects. The Josephson effect in a superconducting loop can also be exploited to exact more control over the nonlinearities of the meta-material.In this thesis, we present Josephson junction based metamaterials with in-situ tunability of second and third-order (Kerr) nonlinearities. We optimized the Josephson junction composites SNAILs, well-known in the superconducting circuits community, for the specific use case of building blocks for an impedance-matched nonlinear meta-material. In such devices, the strong third-order (Kerr) nonlinearity can be tuned from positive to negative values. To demonstrate the efficacy of this phenomenon, we have shown a use case of the meta-material as a TWPA with a new phase-matching mechanism: reversed Kerr phase matching, which utilizes the sign reversal of the Kerr nonlinearity to correct for the dispersion curvature of such devices arising due to its finite plasma. The meta-material operated as reversed Kerr TWPA exhibits up to 4 GHz wide combined amplification band with 8 GHz dynamic band tunability, -98 dBm saturation (1 dB compression point) around 20 dB gain, and amplifier added noise close to the standard quantum limit. The absence of any gaps in the transmission can provide a continuous amplification band with significantly lower gain ripples in contrast to the previously demonstrated TWPAs with dispersion engineering.We also present the generation of entanglement utilizing the metamaterials to demonstrate their versatility and further emphasize their potential in the general framework of nonlinear microwave quantum optics. Due to their large bandwidth, these devices have been identified as promising for generating two-mode squeezing and broadband entanglement. With a device optimized for the generation of broadband entanglement, we observed entanglement between two modes separated by up to 400 MHz. We measured logarithmic negativity between 0.27 and 0.51, and the collective quadrature squeezing below the vacuum limit between 1.5 and 2.1 dB. The presented proof-of-principle results can pave the way towards the implementation of Josephson junction based metamaterials in novel applications, including non-destructive single-photon detection, single-photon measurement and control in c-QED, photon-based quantum computing, precision sensing, the detection of dark matter, and quantum illumination.
•Nov 7, 2022•0 citations