RESEARCH

We categorize our research into three primary areas:

Electrons on liquid helium: By leveraging the pristine environment of the electron-on-helium system, we aim to realize scalable electron spin qubits.

Electrons on solid neon: With electrons on solid neon, by making use of their long coherence times for both charge and spin states, we aim to realize quantum memory.

Cryogenic electronics: We are developing cryogenic electronics required for scaling up the number of qubits, especially focusing on the development of cryogenic microwave sources.

Outlined below are our research accomplishments and ongoing initiatives on more specific topics:

Helium quantum computer

We study floating electrons on the surface of liquid helium, especially in terms of its application to quantum computation. This physical system is free of defects or impurities since the electrons exist in a vacuum. Thanks to its cleanliness, the quantum states of the electrons on helium are expected to have a long coherence time, which provides a perfect platform to realize qubits with. We have worked on the hydrogen-like quantized states (Rydberg states) of many electrons so far and eventually, we aim to control the spin state of a single electron.

For more details please see our paper in Applied Physics Letters (APL). The paper was featured on the cover and was also highlighted in Scilight.

Detection of the Rydberg states of electrons on helium using an LC resonator

To take advantage of the long spin coherence time of electrons on helium, we propose to create a hybrid qubit by coupling the hydrogen-like Rydberg state to the spin state. Quantum information is held in the spin state, which is read out through the Rydberg state. It then needs to be possible to measure the Rydberg state of a single electron.

Recently, We have successfully detected the Rydberg transitions of many electrons on liquid helium using an LC resonator. We are currently adapting this technology to the Rydberg state of a single electron.

Additionally, we measured the strong coupling between photons in the LC resonator and the collective motions of many electrons (plasmon). By leveraging the strong coupling between the plasmon and photons in the resonator, along with the substantial coupling between the Rydberg state and the plasmon, we are attempting to measure the plasmon-mediated transitions of the Rydberg states using the LC resonator to enhance the signal strength.

Spin quantum memory on neon

We are exploring the realization of spin memory using electrons on solid neon for integration with other types of qubits. To achieve this, we are currently performing experiments with NbTiN nanowire resonators.

Cryogenic microwave source

We aim to realize cryogenic electronic circuits that are indispensable for a scalable quantum computer. Currently, we are developing a cryogenic microwave source using a tunnel-diode-oscillator (TDO).

The main result, as shown in the figure below, is the achievement of better amplitude stability compared to a commercial microwave source, which would improve the qubit readout fidelity.

For more details, please see our preprint.

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