Ryoichi Ishihara

Associate Professor, Group leader

Qutech, Dep. Quantum and Computer Engineering, Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology

Ishihara-lab focuses on the integration technologies for unconventional electronic systems; quantum computers, quantum sensors, neuromorphic computers, and biodegradable sensors. Our work involves new materials, scalable fabrication of electronic and photonic devices, and 3D heterogeneous integration, aiming to realize unconventional electronic systems.

Quantum gravity sensor using levitating micromagnet and spins in diamond

This is a collaboration project with European Space Research and Technology Center ESTEC.

A high-precision gravity sensor or gravimeter is an important device and key measurement equipment for navigation and gravitational signal detection in space. The sensor could be envisioned to be used for the measurement of underground structures or hidden natural resources on Earth or Earth’s gravity field from space [1]. The system should have a very compact and robust design required by the demanding constraints of the satellite and rocket in terms of mass, volume, power consumption, and reliability against radiation and vibration.

In the field of gravimeters or accelerometers, the optomechanical system using MEMS technology [2] is a well-matured technology. However, the sensitivity in the order of 10^-7 m/s²/Hz^1/2 is much higher than the required value of 5×10^-11 m/s²/Hz^1/2. In recent years there has been progressed in the development of highly accurate accelerometers using quantum effect aiming for high-precision gravity sensing. Atom interferometer uses detection of the motion of ultra-cold atoms and change of light intensity in an interferometer [3]. Although the sensitivity of 5×10^-10 m/s²/Hz^1/2 is approaching the requirements, the overall system size is inherently too large to be mounted in a satellite and lacks reliability because it uses open-space and fiber-based optical setup and many mechanical parts.

To meet all the requirements of high sensitivity, compactness, and robustness, a quantum bit in a solid-state system integrated with the center of mass motion of a levitated magnetic particle will be attractive. Levitated micro-magnet is reported to provide a very high Q factor because of the completely isolated system from the environment [4,5]. The color center in a diamond, such as nitrogen-vacancy [6], contains an optically active single electron spin that is sensitive to the magnetic field generated by the levitated micromagnet whose position is changed by gravity and its state can be read out by light. Theoretical study of the system operating at a cryogenic temperature of 4K predicts a very high sensitivity approaching 10^-13 m/s²/Hz^1/2,[7] well beyond the requirement. However only one of these studies actually coupled this magnet to a spin qubit [8].

In the study, a small micro-magnet will be levitated and coupled to an NV center for quantum sensing demonstration.

References:

1. Quantum Sensor Sees Beneath the Beneath, C.Q.Choi, IEEE Spectrum (2022) https://spectrum.ieee.org/quantum-sensors-gravity-birmingham
2. F. Monteiro, W. Li, G. Afek, et al., “Force and acceleration sensing with optically levitated nanogram masses at microkelvin temperatures,” Phys. Rev., vol. 101, 2020, Art no. 053835
3. Z.-K. Hu, B.-L. Sun, X.-C. Duan, et al., “Parametrized modified gravity constraints after Planck,” Phys. Rev., vol. 88, 2013, Art no. 043610
4. Markus Aspelmeyer, Tobias J. Kippenberg, and Florian Marquardt. Cavity optomechanics. Reviews of Modern Physics, 86(4):1391–1452, 12 2014.
5. M. Rademacher, et al., Adv. Opt. Techn. 2020; 9(5): 227–239
6. F. Jelezko, J. Wrachtrup, “Single defect centres in diamond: A review”, Phys. Stat. Sol. (a) 203, 13, 3207 (2006)
7. J. Prat-Camps, C. Teo, C. C. Rusconi, W. Wieczorek, and O. Romero-Isart, Ultrasensitive Inertial and Force Sensors with Diamagnetically Levitated Magnets, Phys. Rev. Applied 8, 034002 (2017).
8. J. Gieseler, A. Kabcenell, E. Rosenfeld, J. D. Schaefer, A. Safira, M. J.A. Schuetz, C. Gonzalez-Ballestero, C. C. Rusconi, O. Romero-Isart, and M. D. Lukin. Single-Spin Magnetomechanics with Levitated Micro-magnets. Physical Review Letters, 124(16), 4 2020.

Interested? Please contact Ryoichi Ishihara r.ishihara@tudelft.nl