Holger Müller

Closed (1) Trapped atom interferometry in an optical cavity

Closed. This professor is continuing with Spring 2021 apprentices on this project; no new apprentices needed for Fall 2021.

Atom interferometry leverages the precision of quantum mechanics to test gravity and fundamental physics. One the experiments in our group uses an optical cavity to facilitate these experiments, and has recently shown that the light bound by a pair of mirrors can be used to levitate an atom in a quantum superposition of two places at once, for a macroscopic duration of time, thus realizing a stationary probe of gravity (1).

1. Probing gravity by holding atoms for 20 seconds. V. Xu, M. Jaffe, C. D. Panda, S. L. Kristensen, L. W. Clark, H. Müller, Science 366, 745-749 (2019)

If our work sounds interesting, please reach out and we can work with you to find a project you find challenging and exciting! Some projects available now include:

1) Controlling residual amplitude modulation in laser frequency stabilization

Characterizing and improving these our laser stabilization schemes may allow our experiment to demonstrate even longer quantum coherence times and higher gravitational sensitivities.

This project involves building an optical setup to characterize servo performance, and may evolve into setting up an active cancellation servo. The student will learn key techniques in experimental atomic physics (e.g. optics, feedback loops, electronics, etc) through this project.

Qualifications: Ideal applications may be upper-division STEM students who have completed advanced electromagnetism or electronics lab courses.


2) Computer Aided Design (CAD) modeling the vacuum system.

This project will involve using CAD (computer-aided design) software to model the existing vacuum chamber setup, and later design and simulate upgrades to the vacuum chamber.


3) Red pitaya (FPGA) auto-locker for laser frequency stabilization

Our experiments are extremely sensitive to the frequency of the lasers used to cool, trap, and manipulate the atoms. However, the frequency of any laser is sensitive to small environmental changes (such as air temperature, pressure, etc), and therefore must be actively controlled. To stabilize the frequency of the lasers used in our experiment, we depend on various electronic components which monitor the laser frequency and automatically respond to any changes that occur.

In this project, you will help program and install electronics to monitor and precisely control the frequency of the lasers used in our experiments.

Qualifications: Applicants have ideally taken an introductory physics class (5A, 7A, or 8A), with interest in pursuing a STEM major.

Weekly Hours: to be negotiated

Related website: http://matterwave.physics.berkeley.edu/cesium-cavity

Closed (2) Atomic gravity gradiometer for airborne gravity surveys

Closed. This professor is continuing with Spring 2021 apprentices on this project; no new apprentices needed for Fall 2021.

Remote laser frequency locking system

The goal of this project is to use a Red Pitaya Field-Programmable Gate Array (FPGA) as an oscilloscope and as a servo to remotely monitor and stabilize (“lock”) the frequency of a diode laser. This remote laser locking system will be used in our ongoing research project, a drone-based atomic gravity gradiometer (FlyG) for airborne gravity surveys (1). Through Wifi, the remote laser locking system will communicate with a laptop computer and transfer the spectroscopy error signal for monitoring.

In this project, an undergraduate student will program a Red Pitaya STEMLAB 125-14 (2) to acquire the error signal from polarization spectroscopy and feedback to frequency-lock the laser frequency. In our group, we have used STEMLAB 125-14 in several research projects. For example, we developed an active vibration isolation stage for an absolute atomic gravimeter, where a STEMLAB 125-14 was programmed as a finite impulse response filter to suppress the low frequency seismic vibration noise (3).

The student will learn atomic techniques for laser frequency stabilization, particularly polarization spectroscopy, and be trained with electronics, particularly proportional-integral controllers. The student will program a graphical user interface running on a laptop computer to monitor the error singla and enable locking. The student will establish the WiFi connection between the STEMLAB 125-14 and the computer, and operate the remote laser frequency locking system via the laptop computer.

1. S. Weiner, X. Wu, Z. Pagel, D. Li, J. Sleczkowski, F. Ketcham, H. Mueller, A flight capable atomic gravity gradiometer with a single laser, IEEE International Symposium on Inertial Sensors and Systems (INERTIAL) (2020).
2. https://www.redpitaya.com/
3. X. Wu, Z. Pagel, B. S. Malek, T. H. Nguyen, F. Zi, D. S. Scheirer, H. Müller, Gravity surveys using a mobile atom interferometer, Science advances 5 (9), eaax0800 (2019).

Weekly Hours: to be negotiated

Off-Campus Research Site: As we have limited access to the lab due to the Covid-19 pandemic, the student will work remotely on hardware set up in the lab. The student will join the daily meetings with the project team, a weekly subgroup meeting with the PI, and a weekly group meeting with the entire team and the PI.

Related website: http://matterwave.physics.berkeley.edu/flyg

Closed (3) Precision measurement with atom interferometry

Closed. This professor is continuing with Spring 2021 apprentices on this project; no new apprentices needed for Fall 2021.

The alpha experiment in our group uses atom interferometry to make a precision measurement of the fine structure constant (1). We're in the building stage of our experiment, and we have several projects available for undergraduate researchers.

(1) Richard H. Parker, Chenghui Yu, Weicheng Zhong, Brian Estey, and Holger Müller, Measurement of the fine-structure constant as a test of the Standard Model, Science 360, 191-195 (2018).

Potential projects include remote work on the statistics / data analysis / simulations, or in-person lab work with the vacuum chamber / electronics / optics / laser systems. We're happy to work with you to find a project you find challenging and exciting!

Weekly Hours: to be negotiated

Related website: http://matterwave.physics.berkeley.edu/cesium-fountain

Closed (4) A laser phase plate for phase contrast electron microscopy

Closed. This professor is continuing with Spring 2021 apprentices on this project; no new apprentices needed for Fall 2021.

Transmission electron microscope images often suffer from low image contrast since the samples under observation tend to be transparent to electrons. This is especially true for biological samples which consist mostly of light elements in delicate molecules which can only be exposed to a small electron dose before being destroyed. Our approach to solving this long-standing problem uses a world-record high-intensity laser beam to exploit quantum mechanical interference of the electrons' wave functions in order to dramatically increase image contrast. As such, our project operates at the confluence of laser optics, molecular biology, and electron microscopy. We are looking for a student who is interested in working closely with our team to help us successfully apply this technique to important problems in biological imaging!


Project ideas include:
-Writing instrument control software
-Learning how to operate a state-of-the-art transmission electron microscope for biological sample data collection
-Designing and building laser optical systems
-Designing and building high-performance analog electronics

Qualifications: Required: -Programming experience (C++, Python, and/or MATLAB preferred)

Weekly Hours: to be negotiated

Related website: http://matterwave.physics.berkeley.edu/phase-contrast-electron-microscopy