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A finite temperature quantum algorithm for the Hubbard model |
Knap |
- Research group
- Collective Quantum Dynamics
- Description
- The goal of the thesis is to develop an analyze finite temperature algorithms for quantum computers. The field is quickly evolving. Please contact me to discuss a concrete project.
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Donors in Strained Silicon for Quantum Applications (topic is not available any more) |
Brandt |
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Emergent (non-linear) hydrodynamics in ultracold quantum gases |
Knap |
- Research group
- Collective Quantum Dynamics
- Description
- Isolated quantum matter can thermalize locally because the surrounding system can act as a path. We will study how hydrodynamics can emerge at late times in such systems. The field of quantum dynamics is quickly evolving. Please contact me directly to discuss a concrete project.
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Fabrication of a superconducting coplanar transmission line for efficient coupling to rare earth spin ensembles |
Gross |
- Research group
- Technical Physics
- Description
- The rare earth spin ensembles are well established by now in the optical domain where the microwave states are used as an intermediate state to extend the storage time [1]. Number of purely microwave manipulations by spin ensembles is very limited and is bound to coupling of spin ensembles to microwave resonating structures [2], which allows amplifying the microwave signal and enhancing the interaction between the ions and the microwave field. The main disadvantage of using these resonating structures is their fixed frequencies and very small tuning range. Typically fabricated in a coplanar design, the superconducting resonators create strongly inhomogeneous distribution of the field within the spin ensemble, which results into largely detuned Rabi frequencies experienced by the spins.
Aim of this project is to fabricate novel design of microwave transmission line, which will allow for homogeneous distribution of the microwave field within the excited rare-earth spin ensemble, and at the same time, will not be bound to a specific frequency. This will allow realizing various spin manipulation schemes, which involve more than two energy levels (beyond Hahn-echo) and thus deploy complex spin-manipulation techniques.
We are looking for a highly motivated master student joining this project. Within the project, you will gain hands-on experience on design and fabrication of superconducting microwave structures. You will design and fabricate superconducting transmission line, which will then be tested at cryogenic conditions when coupled to rare earth spins ensembles.
[1] Kinos, A. et al. Roadmap for Rare-earth Quantum Computing. arXiv 2103.15743 (2021).
[2] Ranjan, V. et al. Multimode Storage of Quantum Microwave Fields in Electron Spins over 100 ms.
https://link.aps.org/doi/10.1103/PhysRevLett.125.210505 (2021).
- Contact person
- Nadezhda Kukharchyk
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Fabrication of a superconducting transmission line resonator in a bad-cavity limit |
Gross |
- Research group
- Technical Physics
- Description
- The rare earth spin ensembles are well established by now in the optical domain where the microwave states are used as an intermediate state to extend the storage time [1]. Number of purely microwave manipulations by spin ensembles is very limited and is bound to coupling of spin ensembles to microwave resonating structures [2], which allows amplifying the microwave signal and enhancing the interaction between the ions and the microwave field. The main disadvantage of using these resonating structures is their fixed frequencies and very small tuning range. Typically fabricated in a coplanar design, the superconducting resonators create strongly inhomogeneous distribution of the field within the spin ensemble, which results into largely detuned Rabi frequencies experienced by the spins.
Aim of this project is to fabricate novel design of microwave transmission line resonator, which would work in a bad-cavity regime and will thus allow to couple to rare-earth spins at a larger badwidth. This will allow realizing various spin manipulation schemes, which involve more than two energy levels (beyond Hahn-echo) and thus deploy complex spin-manipulation techniques.
We are looking for a highly motivated master student joining this project. Within the project, you will gain hands-on experience on design and fabrication of superconducting microwave structures. You will design and fabricate superconducting resonating structure, which will then be tested at cryogenic conditions when coupled to rare earth spins ensembles.
[1] Kinos, A. et al. Roadmap for Rare-earth Quantum Computing. arXiv 2103.15743 (2021).
[2] Ranjan, V. et al. Multimode Storage of Quantum Microwave Fields in Electron Spins over 100 ms.
https://link.aps.org/doi/10.1103/PhysRevLett.125.210505 (2021).
- Contact person
- Nadezhda Kukharchyk
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Fabrication of low-loss Josephson parametric devices |
Gross |
- Research group
- Technical Physics
- Description
- Superconducting Josephson devices represent one of the leading hardware platforms of modern quantum information processing. In particular, these devices often employ nonlinear parametric effects for tunable coupling schemes or quantum-limited amplification. Such effects can be also used in a multitude of quantum communication & sensing protocols. In this context, a particular challenge arises due to the fundamental requirement for minimizing losses in superconducting systems in order to preserve the fragile quantum nature of related microwave states. To this end, one needs to develop advanced routines for fabrication of low-loss Josephson parametric amplifiers & parametric couplers by exploring various surface treatment approaches or studying novel superconducting materials. The low-loss Josephson devices are to be used in our ongoing experiments towards experimental investigation of particular novel concepts, such as the quantum radar or remote entanglement distribution protocols.
This master thesis will involve designing superconducting parametric circuits, cleanroom fabrication, and characterization measurements of fabricated devices with an aim to employ these in microwave quantum communication & sensing experiments.
- Contact person
- Kirill Fedorov
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Fractonic quantum matter at low temperatures |
Knap |
- Research group
- Collective Quantum Dynamics
- Description
- Fractonic quantum matter possesses excitations with constrained mobility. In two dimensions, excitations can for example only move on one dimensional lines. The goal of this thesis is to study either with numerical or field theoretical techniques their ground state and dynamical properties. The field of fractions is quickly evolving. Please contact me directly to discuss a concrete project.
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Generating small magnetic fields inside an open-end magnetic shielding with a superconducting solenoid magnet (topic is not available any more) |
Gross |
- Research group
- Technical Physics
- Description
- Coherence times of hyperfine transitions of rare earth spin ensembles reach seconds and hours. Particularly, this is possible due to cooling these ensembles down to ultra-low temperatures and taking advantage of Zero First-Oder Zeeman shift transition (ZEFOZ). These ZEFOZ transitions require very precise adjustment of magnetic field, in order to reach the very extremum point with the longest coherence time. Moreover, employing ZEFOZ transition allows working at near-zero magnetic fields [1], which paves the way towards the quantum memory for the superconducting qubits.
To have a precise control of the magnetic field at near zero field range, it is necessary to remove or strongly reduce any external background magnetic fields. Alternative way would be to confine the magnetic field and align them along a single axis. Controllably applying another external magnetic field along the same axis, would allow accessing a desired operational point with lowest coherence in a highly controllable way.
The goal of this master project is to build such a semi-shielded solenoid magnet with a sample space, which will allow for reaching a desired ZEFOZ point at near-zero magnetic field.
We are looking for a highly motivated master student joining this project. Within the project, you will learn about practical realization of magnetic shielding and superconducting magnets. You will design an experimental magnetically controlled sample space for spin-ensemble quantum memories.
[1] Y.-H. Chen et al. „Coupling erbium spins to a three-dimensional superconducting cavity at zero magnetic field”, Phys. Rev. B, vol. 94, p. 075117, Aug 2016
- Contact person
- Nadezhda Kukharchyk
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Hybrid quantum teleportation |
Gross |
- Research group
- Technical Physics
- Description
- Microwave quantum communication is a novel field of science and technology, where one exploits quantum properties of propagating microwave signals to achieve quantum advantage in various communication scenarios. Here, a particularly important protocol is quantum teleportation, where one bypasses fundamental limitations on fidelity of transferred quantum states by exploiting shared entanglement. In this context, an open challenge is teleportation of the most exotic, non-Gaussian, quantum states, such as Fock or Schrödinger cat states, with the help of Gaussian entangled states. In theory, this problem can be addressed by using non-deterministic approaches or incorporating non-Gaussian operations in the teleportation protocol.
This master thesis will focus on a theory analysis & numerical simulation of quantum microwave teleportation of non-Gaussian quantum states. Later stages of this master project may include experimental investigation of proof-of-principle hybrid quantum teleportation protocols based on superconducting quantum circuits in the cryogenic environment.
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Magnetic resonance spectroscopy in two dimensional ferromagnets |
Gross |
- Research group
- Technical Physics
- Description
- Dimensionality crucially influences the properties of materials. Two-dimensional (2d) van der Waals materials in the monolayer limit are presently heavily investigated. Within this class of materials systems with magnetic order exist, yet only limited insights have been obtained with respect to their magnetic excitation properties. A major experimental challenge is the small volume and thus low number of spins in these systems. Thus, high sensitivity techniques and large filling factors are key for successful studies of these materials. The goal of this thesis is to use planar superconducting resonators in combination with 2d van der Waals ferromagnets to study magnetic excitations at low temperatures by microwave spectroscopy.
You will work on implementing the microwave-based spectroscopy of magnetic excitations in 2d systems. You will use state-of-the-art nanofabrication techniques like electron beam lithography and thin film deposition machines for the superconducting resonators. You will also gain experience in cryogenic microwave spectroscopy utilizing vector network analyzing techniques. Another important aspect will be the development of a quantitative model to illuminate the underlying physics of the magnetic excitations.
- Contact person
- Matthias Althammer
- Hans-Gregor Hübl
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Magnon-mechanics in suspended nano-structures |
Gross |
- Research group
- Technical Physics
- Description
- Nano-mechanical strings are archetypical harmonic oscillators and can be straightforwardly integrated with other nanoscale systems. For example, the field of nano-electromechanics studies the coupling of nano-strings to microwave circuits, which resulted in the creation of mechanical quantum states and concepts for microwave to optics conversion. Here, we plan to investigate an alternative hybrid system based on ferromagnetic nanostructures integrated with nano-strings or nano-mechanical platforms. These hybrid devices aim at the efficient conversion between phonons and magnons with the potential to interact with light and are thus ideal candidates for conversion applications.
We are looking for a motivated master student for a nano-mechanical master thesis in the context of magnon-phonon interaction. The goal of your project is to investigate the static and dynamic interplay between the mechanical and magnetic properties of a nano-mechanical system sharing an interface with a magnetic layer. In your thesis project, you will fabricate freely suspended nanostructures based on magnetic thin films using state-of-the-art nano-lithography and deposition techniques. Further, you will probe the mechanical response of the nano-structures using optical interferometry while exciting the magnetization dynamics of the magnetic system.
- Contact person
- Matthias Althammer
- Hans-Gregor Hübl
- Stephan Geprägs
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Microwave cryptography with propagating quantum tokens |
Gross |
- Research group
- Technical Physics
- Description
- Quantum cryptography based on continuous-variables is a rapidly growing field of fundamental and applied research. It deals with various topics regarding fundamental limits on data communication & security. In particular, the microwave branch of quantum cryptography demonstrates a large potential for near term applications due to its natural frequency compatibility with the upcoming 5G and future 6G networks. In this context, we plan to investigate microwave photonic states, quantum tokens, which can be used for unconditionally secure storage and transfer of classical information. This security properties are provided by a peculiar combination of the quantum no-cloning theorem and vacuum squeezing phenomenon. The latter effect can be routinely achieved in the microwave regime with superconducting Josephson parametric amplifiers, which we plan to use for experimental generation & investigation of quantum token states.
This master thesis will focus on developing numerical & experimental tools for the ongoing microwave quantum cryptography experiments. This includes programming various elements of FPGA data processing routines, performing cryogenic measurements with propagating microwaves, and analyzing measurement data for quantifying quantum correlations & unconditional security in propagating quantum token states.
- Contact person
- Kirill Fedorov
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Nano-electromechanics in the non-linear regime |
Gross |
- Research group
- Technical Physics
- Description
- Circuit nano-electromechanics is a new field in the overlap region between solid-state physics and quantum optics with the aim of probing quantum mechanics in macroscopic mechanical structures. We employ superconducting circuits to address fundamental questions like the preparation of phonon number states in the vibrational mode and the conversion of quantum states between the mechanical element and the microwave domain. The initial successful experiments of the group include hybrid devices based on nano-string resonators inductively coupled to frequency tunable microwave resonators. This setting allows to explore large optomechanical single photon rates, enables intrinsic amplification schemes, and hereby allows to access a new regime of light matter coupling.
The goal of your thesis is the development and fabrication of hybrid devices based on frequency tunable superconducting microwave resonators with integrated nanomechanical string-resonators as well as their spectroscopy. This includes the design and fabrication of these devices, where you will use state-of-the-art simulation and nano-fabrication techniques. The second main aspect of your thesis is their investigation using highly sensitive microwave spectroscopy techniques in a low-temperature environment.
- Contact person
- Hans-Gregor Hübl
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Nanophotonische Silizium-Resonatoren mit einstellbarer Frequenz für Quantennetzwerke |
Reiserer |
- Research group
- Quantum Networks
- Description
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The implementation of global quantum networks is among the most intensely pursued research topics in quantum science and technology. Besides being of fundamental interest, such systems would also allow for numerous applications by connecting remote quantum computers and quantum sensors in order to enhance their capabilities. To implement such networks, one needs efficient hardware, in which stationary quantum bits are connected by optical photons, ideally in the "telecommunications window" where loss in optical fibers is minimal. We have recently established erbium-doped silicon nanophotonic resonators as a promising experimental platfrom that allows for the fabrication of quantum network nodes using established techniques of the semiconductor industry. However, to unleash this potential, a method to reliably tune many resonators on a single chip is an outstanding challenge. In this thesis, this will be developed by using laser oxidation tuning or nanomechanical actuation.
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Non-reciprocal magnonic devices |
Gross |
- Research group
- Technical Physics
- Description
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Spin waves (magnons) are the quantized excitations of the magnetic lattice in solid state systems. The field of magnonics is exploring concepts to use these magnons for information transport and processing. Of particular interest is to achieve non-reciprocity for opposite spin wave propagation directions, which can be realized in hybrid structures of a periodic artificial magnetic array on top of a magnonic waveguide. These systems would be potential candidates for compact microwave directional couplers and circulators operational at low temperatures. The goal of this thesis is to develop and optimize such nonreciprocal devices based on periodic magnetic arrays. This implementation is a first step towards compact low temperature microwave circuits relevant for superconducting quantum circuits.
You are a resourceful master student willing to contribute with your thesis towards the successful implementation of nonreciprocal microwave devices at cryogenic temperatures. You will use state-of-the-art nanofabrication techniques using electron beam lithography and thin film deposition machines to design your hybrid systems. You will also gain experience in cryogenic microwave spectroscopy utilizing vector network analyzing techniques. Utilizing a combination of numerical and analytical models, you will drive the optimization of such hybrid devices.
- Contact person
- Hans-Gregor Hübl
- Stephan Geprägs
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Optical detection of magnetization dynamics at low temperatures |
Gross |
- Research group
- Technical Physics
- Description
- Utilizing magneto-optical effects enables the investigation of excitations in magnetic systems like magnons or spin waves down to the sub-micrometer scale. In this way, one can probe spin wave propagation in micro-patterned ferromagnetic materials, which is highly relevant for spintronic applications as well the investigation of tailored quantum systems. Especially at low temperatures, novel magnetic phases exist with intriguing magnetization dynamic properties. The goal of this thesis is the optical investigation of spatially resolved magnetization dynamics in spintronic devices as well as hybrid quantum systems at cryogenic temperatures.
We are searching for a highly motivated master student to start the experiments on optically detected magnetization dynamics at cryogenic temperatures. You will improve the optical setup used for the detection of magnetization dynamics to increase the sensitivity. In addition, you will work with state-of-the-art microwave equipment to drive the magnetization dynamics in spintronic devices and hybrid systems. After assessing the performance of the setup with state-of-the-art magnetic systems, you will work in the clean room facilities of our institute to carry out the microfabrication steps to define your own spintronic devices or hybrid systems.
- Contact person
- Matthias Althammer
- Hans-Gregor Hübl
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Optomechanics with Single Photons |
Poot |
- Research group
- Quantum Technologies
- Description
In optomechanics, light is used to measure and alter the dynamics of mechanical resonators. It is by far the most sensitive method to observe the tiny vibrations that nanomechanical devices perform: in one second one can determine their position with femtometer precision! Using light to measure the mechanics is not the only aspect of optomechanics. The same light can also be used to change the dynamics of the mechanical device through a process called cavity backaction. The photons exert a force on the resonator, the so-called radiation pressure. In this project we want to explore the ultimate limits to this force. The goal is to measure the force originating from a single photon! For this it is required that the photon interacts with the mechanical resonator as strongly as possible. For this we need to the design and make very low loss optical cavities, such as microring resonators. Also, the mechanical device should have a quality factor as high as possible. You will make both the optical and mechanical components from chips with highly-stressed silicon nitride using state-of-the-art nanofabrication in the cleanroom. Then the devices are placed in a vacuum chamber for their measurement. In our highly-automated setup you can very quickly characterize many of the devices on your chip. Then, with the perfect device parameters you can start to explore the more advanced measurements. Initially we can measure the devices in with pulsed light, but by using single photons we want to explore the ultimate limits to optomechanical forces.
See http://www.groups.ph.tum.de/en/qtech/openings/ for a detailed description of this project.
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Photonen-Emitter in kontrolliert verspannten, nanophotonischen Silizium-Wellenleitern |
Reiserer |
- Research group
- Quantum Networks
- Description
- The implementation of global quantum networks is among the most intensely pursued research topics in quantum science and technology. Besides being of fundamental interest, such systems would also allow for numerous applications by connecting remote quantum computers and quantum sensors in order to enhance their capabilities. To implement such networks, one needs efficient hardware, in which stationary quantum bits are connected by optical photons, ideally in the "telecommunications window" where loss in optical fibers is minimal. We have recently established erbium-doped silicon nanophotonic resonators as a promising experimental platform that allows for the fabrication of quantum network nodes using established techniques of the semiconductor industry. To unleash this potential, a detailed understanding of the effects of crystalline strain on the properties of the emitted photons is required. This will be investigated in this thesis.
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Quantum Optics on a Chip |
Poot |
- Research group
- Quantum Technologies
- Description
Quantum optics is an extremely powerful approach towards quantum communication, quantum sensing, and quantum computing. In particular, quantum information stored in photons has very low decoherence and can be transmitted over large distances through optical fibers. To date, most experiments in quantum optics use optical tables full with mirrors and beam splitters that all have to be carefully aligned and stabilized. This may be good enough for initial demonstrations, but in order to bring quantum science into the realm of quantum technology, a more scalable approach is required.
With our expertise in making photonic chips using advanced nanofabrication, we are making putting these exciting quantum optics experiments on chips. Here, light is routed via optical waveguides. Furthermore, by bending a waveguide, one gets the equivalent of a free-space mirror; a beam splitter cube becomes a directional coupler and so on. By combining these elements, we can make the building block for e.g. an optical quantum computer. With that, the possibilities are almost unlimited.
For such large-scale optical quantum circuits we also want to incorporate single-photon sources, superconducting single-photon detectors, and optomechanical phase shifters. This all happens on a single chip. Making and characterizing the components is the first step and from there on, you are making more and more complex quantum chips. You will be doing the nanofabrication in the cleanroom, and then use our optical measurement setups to see how each device is performing. Depending on your preference, it may also be possible to add a modelling component to the project.
See http://www.groups.ph.tum.de/en/qtech/openings/ for a detailed description of this project.
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Remote entanglement of superconducting qubits |
Gross |
- Research group
- Technical Physics
- Description
- Quantum computing represents a promising information processing paradigm exploiting quantum properties, such as superposition and entanglement. The latter entity is crucial for achieving quantum advantage in scalable quantum information processing with distributed quantum computers, including those built with superconducting qubits. Here, an important task is to study how quantum entanglement can be distributed between remote superconducting qubits. To this end, we plan to exploit propagating two-mode squeezed states as a carrier of quantum entanglement. We intend to analyze their interactions with remote superconducting quantum bits in theory & verify our findings in experiments.
This master thesis will first focus on theory & numerical simulations of remote entanglement of superconducting qubits with propagating squeezed light. Later project stages may also include cryogenic experiments with superconducting transmon qubits & Josephson parametric amplifiers towards verifying novel concepts of remote entanglement.
- Contact person
- Kirill Fedorov
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Sensing magnetic resonance via nitrogen vacancy centers |
Gross |
- Research group
- Technical Physics
- Description
- Electron spin resonance provides means to very sensitive magnetic field sensors. At present charged nitrogen vacancies in diamond provide unique properties such as optical readout of the electron spin state and spin coherence above room temperature. This allows using this system for magnetic field sensing applications. You will work on implementing an experimental platform for optical readout and microwave manipulation of electron spins in nitrogen vacancy centers in your thesis. The ultimate goal is the detection of magnetic resonance via nitrogen vacancy centers in the new setup.
We are searching a skilled master student to start the experiments on optically detected electron spin resonance. You will optimize the optical setup used for the detection of spin dynamics to improve the noise floor. In addition, you will work with state-of-the-art microwave equipment to drive the magnetization dynamics of the electron spin. After assessing the performance of the setup with state-of-the-art magnetic systems, you will work on detecting magnetic resonance phenomena in solid state systems.
- Contact person
- Matthias Althammer
- Hans-Gregor Hübl
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Strong electrostatic effects in optomechanical devices |
Poot |
- Research group
- Quantum Technologies
- Description
Optomechanics provides extremely sensitive methods to measure the displacement of mechanical resonators. However, the forces are much smaller in optomechanics compared to those in nanoelectromechanical systems (NEMS). The goal of the project is to make, and measure opto-electromechanical devices which have strong electrostatic interactions. This includes the electrostatic spring effect where the resonance frequency depends strongly on the applied voltage. The next step is trying to measure the potential by measuring the ringdown of different mechanical modes. The devices will be made using advanced nanofabrication techniques such as electron beam lithography and reactive ion etching.
See http://www.groups.ph.tum.de/en/qtech/openings/ for a detailed description of this project.
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Theoretical Solid State Physics |
von Delft |
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