MM
M.A. Morssink
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The recent quest for large resonator photon numbers in circuit quantum electrodynamics (cQED) has led to the discovery of ionization in Transmon-resonator systems. Ionization compromises the quantum non-demolition nature of Transmon readout. Furthermore, it can lead to dephasing in elements coupled to the Transmon, which is detrimental to optomechanical schemes using an auxiliary qubit to create quantum states. Since the transverse nature of the usual dipolar capacitive coupling lies at the origin of ionization, our team engineered a new parametric coupling scheme that can potentially suppress ionization by being inherently more longitudinal.
Using a large detuning in combination with parameters chosen based on branch analysis, ionization in the system was largely suppressed. This suppression enabled the observation of the collapse and revival of the Transmon potential under parametric coupling at high resonator photon numbers. The measured Transmon Stark shift indicates a collapse of the potential at 12,300 photons and a subsequent revival, in agreement with the derived theoretical model. Resonator phase-space measurements further confirmed the collapse and revival. The newly identified revived regime potentially enables coherent Transmon operation at high photon numbers. ...
Using a large detuning in combination with parameters chosen based on branch analysis, ionization in the system was largely suppressed. This suppression enabled the observation of the collapse and revival of the Transmon potential under parametric coupling at high resonator photon numbers. The measured Transmon Stark shift indicates a collapse of the potential at 12,300 photons and a subsequent revival, in agreement with the derived theoretical model. Resonator phase-space measurements further confirmed the collapse and revival. The newly identified revived regime potentially enables coherent Transmon operation at high photon numbers. ...
The recent quest for large resonator photon numbers in circuit quantum electrodynamics (cQED) has led to the discovery of ionization in Transmon-resonator systems. Ionization compromises the quantum non-demolition nature of Transmon readout. Furthermore, it can lead to dephasing in elements coupled to the Transmon, which is detrimental to optomechanical schemes using an auxiliary qubit to create quantum states. Since the transverse nature of the usual dipolar capacitive coupling lies at the origin of ionization, our team engineered a new parametric coupling scheme that can potentially suppress ionization by being inherently more longitudinal.
Using a large detuning in combination with parameters chosen based on branch analysis, ionization in the system was largely suppressed. This suppression enabled the observation of the collapse and revival of the Transmon potential under parametric coupling at high resonator photon numbers. The measured Transmon Stark shift indicates a collapse of the potential at 12,300 photons and a subsequent revival, in agreement with the derived theoretical model. Resonator phase-space measurements further confirmed the collapse and revival. The newly identified revived regime potentially enables coherent Transmon operation at high photon numbers.
Using a large detuning in combination with parameters chosen based on branch analysis, ionization in the system was largely suppressed. This suppression enabled the observation of the collapse and revival of the Transmon potential under parametric coupling at high resonator photon numbers. The measured Transmon Stark shift indicates a collapse of the potential at 12,300 photons and a subsequent revival, in agreement with the derived theoretical model. Resonator phase-space measurements further confirmed the collapse and revival. The newly identified revived regime potentially enables coherent Transmon operation at high photon numbers.
Controlling the Quantum
Creating a protocol for arbitrary state generation in an LC oscillator using Jaynes-Cummings interactions
Producing arbitrary quantum states in mechanical oscillators is an essential part of the research con- cerning combining the theory of quantum mechanics with general relativity. In recent years, a lot of progress was made by the development of optomechanics and circuit quantum electro dynamics using which a quantum mechanical interaction between an LC oscillator and a mechanical oscillator can be created. This only left the need for the ability to create arbitrary desired states in an LC oscillator while keeping its properties as a linear resonator in tact. The interaction needed for this was recently designed in the group and is called the photon-pressure interaction. Using this interaction, effectively a Jaynes-Cummings interaction between a qubit and a LC oscillator was created which can truly be turned on and off, keeping the linear properties of the LC oscillator while the interaction is turned off. In this thesis a protocol that makes use of the Jaynes-Cummings interaction and qubit drives to create arbitrary states in the LC oscillator is developed. To show that the desired oscillator state has been created a protocol is also developed to perform Wigner tomography on the LC oscillator. Both protocols have been tested using simulations with loss effects corresponding to the ones encountered in our lab setting. The simulation results show that using the current lab system settings, states can successfully be produced in the LC oscillator and measured using the tomography protocol. This paves the way for arbitrary state generation and state measurement experimentally in the lab.
...
Producing arbitrary quantum states in mechanical oscillators is an essential part of the research con- cerning combining the theory of quantum mechanics with general relativity. In recent years, a lot of progress was made by the development of optomechanics and circuit quantum electro dynamics using which a quantum mechanical interaction between an LC oscillator and a mechanical oscillator can be created. This only left the need for the ability to create arbitrary desired states in an LC oscillator while keeping its properties as a linear resonator in tact. The interaction needed for this was recently designed in the group and is called the photon-pressure interaction. Using this interaction, effectively a Jaynes-Cummings interaction between a qubit and a LC oscillator was created which can truly be turned on and off, keeping the linear properties of the LC oscillator while the interaction is turned off. In this thesis a protocol that makes use of the Jaynes-Cummings interaction and qubit drives to create arbitrary states in the LC oscillator is developed. To show that the desired oscillator state has been created a protocol is also developed to perform Wigner tomography on the LC oscillator. Both protocols have been tested using simulations with loss effects corresponding to the ones encountered in our lab setting. The simulation results show that using the current lab system settings, states can successfully be produced in the LC oscillator and measured using the tomography protocol. This paves the way for arbitrary state generation and state measurement experimentally in the lab.