Theory of Microwave Photon Doubling With Josephson Parametric Converter

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Perustieteiden korkeakoulu | Bachelor's thesis
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Date

2025-09-05

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Quantum Technology

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SCI3103

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Aalto Bachelor’s Programme in Science and Technology

Language

en

Pages

40

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Abstract

Quantum technology stands at the forefront of a technological revolution and has become a central focus of modern physics in recent decades. By exploiting the principles of quantum mechanics, such as superposition and entanglement, it enables capabilities beyond the reach of classical devices. These include enhanced computational power (quantum computing), secure information transfer (quantum communication), and high-precision measurements (quantum sensing and metrology). These capabilities often rely on the precise generation, control, and conversion of microwave photons. However, many aspects of their manipulation remain unexplored and require further study to uncover new possibilities. This thesis focuses on one class of devices known as the Josephson parametric converter (JPC). In its conventional implementation, the JPC leverages three-wave mixing to realize quantum-limited amplification and noiseless frequency conversion. Since these applications have been extensively studied, this work considers a modified variant with one junction removed, thereby enabling four-wave mixing. The aim is to analyze this variant to determine whether photon doubling can be achieved with such a relatively simple circuit. Using the normal-mode formalism, the analysis shows that the photon-doubling coefficients are maximized when the junction is biased at half a flux quantum. Numerical simulations relied on a Floquet approach and Suzuki-Trotter decomposition to model the time evolution of the circuit and verify the occurrence of photon doubling. The simulations indicate that the minimal three-junction JPC can theoretically achieve unity conversion for photon doubling, as verified for initial photon populations $n=1$ and $n=2$. However, achieving full conversion requires accounting for Stark shifts, conversion speed, and drive frequency precision. Since this device now employs four-wave mixing, its potential should be further explored. With these new capabilities, it is worth investigating whether it can support operations beyond photon doubling, such as the generation of multiphoton states and squeezed states.

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Supervisor

Möttönen, Mikko

Thesis advisor

Vadimov, Vasilii

Keywords

Josephson parametric converter, photon doubling, superconducting circuits

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https://urn.fi/URN:NBN:fi:aalto-202510218388

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[kand] Perustieteiden korkeakoulu / SCI