Title: Studies of Parametric Devices: Josephson Parametric Amplifier and Josephson Parametric Converter for Amplification and Two-Mode Correlations
Speaker: Ms. Lipi Arvind Bhai Patel
Supervisor: Prof. Baladitya Suri (IAP)
Time/Date: 10:30 AM / 21st April 2026
Venue: S V Narasaiah Auditorium, IAP Department
Abstract:
Quantum Computing and Quantum Information rely on quantum mechanical principles to gain advantages over classical systems. The basic unit of information is the
qubit, which is the quantum analog of the classical bit. Accurate qubit readout is a key requirement for dependable gate operations and the implementation of quantum algorithms. To enable this, Josephson parametric devices such as JPAs, JPCs, and TWPAs are widely used.
This thesis presents detailed theoretical and experimental studies of Josephson Para-
metric Amplifiers (JPAs), Josephson Parametric Converters (JPCs), and their engineer-
ing. The first part of the thesis focuses on JPAs with full sine nonlinearity. This is followed by the introduction of the Impedance-Engineered Josephson Parametric Am-
plifier with Single-Step Lithography. Here, we develop a first-principles theoretical model to compute the gain of an impedance-engineered JPA, explicitly accounting for
the full nonlinearity of both the JPA and the impedance transformer. This work marks a significant advancement over earlier models, which were restricted to lowest-order
nonlinearities and linear transformers. Furthermore, the complete device is experimentally realized using a single-step e-beam lithography process.
In the second part of the thesis, we discuss the three-wave mixing non-degenerate amplification mode of the Josephson Parametric Converter (JPC). Experimental results from the fabricated device are presented, followed by the development of a theoretical model for impedance engineering in JPCs. This approach enables broadband amplification at two distinct frequencies. The impedance engineering is carried out using the self-energy formalism, extending the earlier work of Tanay Roy.
In the final part of the thesis, we discuss the generation of Two-Mode Squeezed (TMS) states using the JPC. We experimentally demonstrate the two-mode correlations in the quantum noise generated by the device. This section further discusses the key factors that can degrade or destroy TMS, and concludes with possible directions for improvement to achieve robust TMS state generation.