5 Ph.D. Positions. Experimental Quantum Physics (The Netherlands) Deadline: Dec. 31, 2019

University of Amsterdam

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Program Details

The Institute of Physics, Faculty of Science at the University of Amsterdam is inviting applications for five Ph.D. positions focusing on Experimental Quantum Physics at its Strontium Quantum Gases Group that is headed by Prof. Florian Schreck and is part of the Quantum Gases and Quantum Information (QG&QI) cluster. The main focus of the group is the exploitation of Sr quantum gases for novel precision measurement techniques and the study of many-body physics.

The five open PhD positions are located at the following four research projects:

Project 1. Continuous atom laser: In this project you will try to build the first continuous atom laser. An atom laser is a beam of atoms that is described by a coherent matter wave. So far only short atom laser pulses have been created by outcoupling a beam of atoms from a Bose-Einstein condensate (BEC). The laser stops working when all atoms of the BEC have been outcoupled, requiring the creation of a new BEC for the next atom laser pulse. BEC creation is usually a lengthy process, requiring several cooling stages to be executed one after the other in time. We have built a machine that can execute these stages one after the other in space, reaching a steady-state sample that is just shy of being a Bose-Einstein condensate. (Our sample has a phase-space density of 1, which is more than 1000 times better than ever before and just a factor 2.6 away from condensation). We have plans to push this machine to a steady-state BEC, to produce atom laser beams, and explore and exploit their properties.
Within this project we have already developed an atomic beam of unprecedented phase-space density in the moving frame, which forms the foundation of project 3 [1, 2]. Insights that you gain to produce the atom laser will also advance project 3 and you will thereby be able to participate in that project as well. You will work in a team with one other PhD student, and PIs Benjamin Pasquiou and Florian Schreck. The work will be executed within a Dutch Vici project, the European Quantum Flagship project iqClock, and the European Innovative Training Network MoSaiQC.

Project 2. Quantum simulation with Rydberg coupled Sr atoms: In this project you will build a quantum simulator based on individual Sr atoms held in optical tweezers and coupled through excitations to Rydberg states. You will load an array of tweezers from an ultracold Sr sample, randomly loading one or zero atoms [3, 4]. Fluorescence of the atoms will tell a computer which tweezers are occupied and enable it to sort the atoms into a desired pattern. These atoms will be coupled by excitations to Rydberg levels. This type of experiment, performed with the alkali element rubidium, has led to spectacular results [5, 6]. The alkaline-earth element Sr has a richer internal state structure than rubidium, which we want to leverage for different types of quantum simulations. You will collaborate with the Dutch Quantum Software Consortium and the Amsterdam research centre QuSoft to define the most interesting tasks for your quantum simulator and perform those quantum simulations. These simulations could span the study of interesting magnetic phenomena to the solution of quantum chemistry challenges. The ultimate goal is to push the quantum simulator into a regime where it can address relevant challenges that cannot be solved using classical computers. You will work in a team of three PhD students and PIs Robert Spreeuw and Florian Schreck.

Project 3. Superradiant Sr clock: In this project you will develop a new type of optical clock: a continuously operating superradiant clock. Optical clocks exploit mHz linewidth transitions of atoms as frequency references and can achieve an accuracy that corresponds to going one second wrong over the lifetime of the universe. Conventional clocks operate by stabilizing a laser on the atomic clock transition and reading out the laser frequency by using an optical frequency comb. The interrogated atoms have to be extremely cold in order for the Doppler effect not to distort the measurement. Preparing a sample of atoms at ultracold temperatures takes time. To bridge that time the clock laser is short-term stabilized on a cavity.

Here we want to improve and simplify the clock by creating a laser from direct emission of light on the clock transition. Since the transition is so narrow an atom will spontaneously emit a photon only every minute or so, which doesn’t give us enough photons to do anything with. To enhance emission we use superradiance. By making it impossible to know which atom in an ensemble emitted a photon, the ensemble will enter a superposition state that is more likely to emit another photon, creating an avalanche effect and usually resulting in a ‘superradiant’ flash of light [7]. The main challenge of this project is to prolong this flash to eternity by feeding new atoms into the superradiantly lasing ensemble. This is challenging since the light used to laser cool the atoms from room temperature to the microKelvin regime decohers the superradiantly lasing ensemble. This challenge can be solved using a new technique that we have developed over the last years within project 1 [1, 2]. We are able to create Sr atomic beams with unprecedented brilliance and steady-state Sr samples close to quantum degeneracy. Crucially, this beam of ultracold Sr atoms is available in a region with very little laser cooling straylight, an important ingredient in feeding a superradiantly lasing ensemble forever.

This project has three parts. In one part we will create a superradiant laser on a kHz-wide transition, collaborating with the group of Jan Thomsen in Copenhagen. In the second part we’ll attempt to build a superradiant clock on a mHz-wide transition of Sr together with the group of Michał Zawada in Torun. The third part will be the exploration of the foundations of superradiant lasing in Amsterdam. Our ideas for this part range from the study of many-body effects in driven-interacting systems, over cavity coupled spin-lattice models, to cavity-cooling of a stream of atoms to quantum degeneracy, forming a continuous atom laser. You will work in a team of two other PhD students, a postdoc, Florian Schreck, and an extensive network of collaborators. The work will be executed with our partners from the European Quantum Flagship project iqClock and the European Innovative Training Network MoSaiQC.

Project 4. RbSr ground-state molecules: In this project you will create ultracold RbS ground-state molecules and use them to perform quantum simulations. RbSr ground-state molecules have a large electric dipole moment and a magnetic moment. These properties enable the tuning of anisotropic long-range interactions between the molecules by applying electric and magnetic fields. After creating the molecules using unusual magnetic Feshbach resonances we discovered [8], your first goal will be to induce repulsive interactions between them, so that they can collide with each other without undergoing chemical reactions. In this way it should be possible to create a quantum gas of molecules. A second research avenue is to confine the molecules in a lattice and induce spin-dependent interactions between them. This will allow you to study interesting models of magnetism.
So far all ultracold ground-state molecules are composed of two alkali atoms. RbSr, composed of an alkali and an alkaline-earth, has a quite different molecular structure, enabling different quantum simulations. In the long-run, the methods you are developing can be used to create molecules that are similar to RbSr and that might enable extremely precise measurements of the electron electric dipole moment, advancing a promising road towards the discovery of physics beyond the standard model.
You will work in a team of two PhD students, one postdoc, PIs Klaasjan van Druten and Florian Schreck, and a network of collaborators. This project is supported by a Dutch research programme on quantum simulation.

Eligibility/ Requirements

You hold a MSc. or equivalent in physics or a related field and are requested to motivate why you apply for the position and to supply a CV.

Other skills/experiences/documents that would benefit your application are:

  • previous experience in an optical, atomic or molecular physics lab;
  • working knowledge of a programming language (matlab, C++ or equivalent);
  • excellent English oral and written communication skills;
  • scientific publications.

To foster diversity in our research group, we will especially appreciate applications from excellent female candidates.

Application Process

You may apply using the link below. Your application must include:

  • a curriculum vitae;
  • a motivation letter that explains why you have chosen to apply for this specific position with a statement of your research experience and interests and how these relate to this project;
  • title and summary of your Master thesis.

Please make sure all your material is attached in only one pdf. The single pdf can be uploaded in the field marked CV in the application form. To accelerate the review of your application, please also send it to Florian Schreck per email.

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