2018 Fiscal Year Annual Research Report
Microwave quantum optics on superconducting circuits
|Research Institution||The University of Tokyo |
中村 泰信 東京大学, 先端科学技術研究センター, 教授 (90524083)
|Foreign Research Fellow
GHEERAERT NICOLAS 東京大学, 先端科学技術研究センター, 外国人特別研究員
|Project Period (FY)
2018-11-09 – 2021-03-31
|Keywords||quantum optics / microwave / quantum information|
|Outline of Annual Research Achievements
On the realization of a unidirectional quantum emitter: the idea here is to use two qubits coupled to a transmission line to create a single quantum emitter that emits in only one direction of the waveguide. This is of key importance for complex quantum architectures. Preliminary simulations of such a two-qubit system coupled to a transmission line are being developed. For now, they involve the following simple protocol: the spontaneous decay of a symmetric or antisymmetric superposition of the qubit states with a single atomic excitation. As expected, preliminary results indicate that the direction of the emission can be influenced by the choice of initial state of the two-qubit system.
On the generation of single magnons: simulations of the qubit-YIG sphere system in a three-dimensional superconducting cavity have been developed. These have allowed to simulate in detail different possible experimental protocols aimed at generating and measuring a single magnon. One protocol involves exciting the third level of the qubit and subsequently transferring that excitation to the YIG sphere. The detuned qubit can then be used to measure the magnon dispersively. The results of these simulations will help
guide the experiments planned for the following financial year.
Finally, part of these four months have been spent discussing with other lab members about the experimental proposals, and elaborating plans for future microwave optics experiments.
|Current Status of Research Progress
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
The simulations carried out during these few months have helped in developing an understanding of the studied physical systems, as well as in developing experimental protocols that will be used during the coming financial year. This will be useful in both the project on the unidirectional quantum emitter, and the project aiming at generating and measuring single magnons. Although it is difficult to provide an assessment of status of the project after only four months, the project seems well on track.
|Strategy for Future Research Activity
On the realization of a unidirectional quantum emitter: the preliminary simulations should now be pushed further in order to obtain precise predictions about the phenomenon of directional emission that is the aim of this project. In particular, it would be pertinent to include the possibility of controlling the rate of emission of the qubits and therefore of defining the shape of the emitted waveforms, as would be the case in the actual experiment. If the results of the simulations are conclusive, fabrication of the device will be the next step. Furthermore, if this experiment is successful, it will also be interesting to investigate using such a device as an isolator.
On the generation of single magnons: performing the experiment is now the next step. Two different protocols have been designed for generating a magnon in the YIG sphere. The first involves exciting the qubit and subsequently bringing it on resonance with the magnons in order to transfer the excitation. In this case, the first step will be to observe vacuum Rabi oscillations. If this is successful, a full Wigner tomography of the magnon
state will be attempted. The second protocol that will be attempted consists in creating a single magnon state via the third excited state of the qubit, and then measuring that state by reading out the qubit which will be dispersively coupled to the YIG sphere.
Time-bin qubit tomography: ways of performing a complete tomography of a time-bin qubit with many modes will be investigated in the context of an ongoing experiment in the lab.
Research Products (1 results)