Department of PhysicsJohn Anderson Research Colloquia

Coordinated with the Colloquia at the Department of Physics and Astronomy of the University of Glasgow. (They may have donuts but we have free chocolate covered biscuits and coffee!)

Colloquia Schedule 2022-2023

* Note: Outside of regular schedule.

Swapan Chattopadhyay (University of Strathclyde) 22nd June 2022, 3pm, JA3.14 

Stochastic phase space cooling using microwave techniques in the GHz frequency range have been employed historically in particle colliders, leading to ground-breaking discoveries. ‘Cooling’ increases the likelihood of observing rare physics events.

The first important advance, conceptual and technological, in this area was stochastic cooling of anti-matter (e. g. ‘antiprotons’) invented by Simon van der Meer (Nobel Prize, 1984), which was instrumental in the discovery of the W and Z Bosons at CERN in 1983 and the ‘top’ quark at Fermilab years later.

Stochastic Cooling reduces the random motion of the beam particles through granular sampling and correction of the beams phase-space structure, thus resembling a ‘Maxwell's demon’. The extension of Stochastic Cooling from the microwave regime up to optical frequencies and bandwidths, samples and exploits a charged particle’s radiation reaction to affect its own phase space, leading to increases in the achievable cooling rates by three to four orders of magnitude.

I will report on the recent first experimental observation of this achievement in the IOTA ring by a Fermilab team.

Fabien Massabuau (University of Strathclyde) 20th July 2022, 3pm, JA3.14

By 2070, the world population is predicted to reach 10.5B inhabitants, and manned space missions as well as settlements on Mars may be on Humanity’s agenda. These predictions forecast extreme pressures on water, food and waste resource management. These challenges are already tangible now, recognised by the United Nations’ Sustainable Development Goals and Net Zero targets.

Ultraviolet (UV) technologies can alleviate these pressures on our Society. The UV range of the electromagnetic spectrum is extremely important with applications including water and air purification, intensive agriculture, medical therapies, and electronics fabrication. Implemented in every household, UV light emission and its monitoring can achieve safe water at the tap, sanitise rooms, or extend shelf-life of food in fridges. Deployed for farming, these technologies can boost crop yields, enable underground farming, and allow reforestation of old farmlands to combat climate change. UV technologies have the potential for substantial impact on the United Nations’ Sustainable Development Goals.

With a bandgap of ca. 5 eV, gallium oxide (Ga2O3) is the leading contender wide bandgap semiconductor for future power electronics and UV sensing application. This compound is highly polymorphic, with the corundum α phase variant (α-Ga2O3) displaying several indisputable assets: (i) it exhibits the largest bandgap (5.3 eV) amongst all phases, (ii) is isostructural with several other semiconducting group-III or transition metal sesquioxides (e.g. In2O3, Ti2O3) and (iii) with the cheap and widely available sapphire (α-Al2O3) substrate.

This presentation will give an overview of the group’s activities on α-Ga2O3 growth, characterisation, bandgap engineering and applications for UV sensing.

Alessandro Rossi (University of Strathclyde) 27th July 2022, 3pm, JA3.14

Quantum technologies for computing, sensing and communicating are developing at a relentless pace. However, a consensus has not been reached on what hardware platforms are the most promising to bridge the prototype-to-product gap and take these systems to commercial fruition. Several solid-state systems are currently under scrutiny, ranging from superconductors to topological insulators, as well as 2D and magnetic materials. Among these, semiconductors occupy a privileged position because they leverage the industrial infrastructure that has enabled modern mainstream electronics for decades. In particular, the prospect of employing well-established Complementary Metal Oxide Semiconductor (CMOS) manufacturing and design techniques could be key to realize large integrated quantum systems of practical use.

In this talk, I will provide an overview of my team’s research on three established semiconductors, namely silicon, germanium, and silicon carbide, which constitute the cornerstones of today’s digital, radio-frequency (rf) and power electronics, respectively. Our mission is to take these materials into the quantum realm and develop devices for quantum computing and quantum metrology applications by preserving full compatibility with the CMOS industrial protocols. To this end, I will show how a field-effect transistor can be turned into a device with quantum functions, namely a quantum dot (QD) with exquisite control of individual charges and spins.1 I will highlight the versatility of this technology by showing that one can virtually use the same QD as either a spin-based information quantum2 or an accurate source of quantised electric current3 for metrological applications. Furthermore, by virtue of ambipolar technology, one can operate such devices to control either conduction electrons or valence holes, each with their own merits for different target applications. Finally, I will argue that, in order to scale up QD-based systems, the interfacing of classical control electronics to the underlying quantum hardware will be one of the crucial challenges. I will discuss these challenges, and possible solutions accessible with the aid of existing CMOS architectures, such as Random Access Memory (RAM) integrated circuitry4 in tandem with rf dispersive readout techniques.2,5

References:

  • [1] Yang et al. Nature Communications 4, 2069 (2013)
  • [2] West et al. Nature Nanotechnology 4, 2069 (2019)
  • [3] Rossi et al. Nano Letters 14, 3405 (2014)
  • [4] Schaal et al. Nature Electronics 2, 236 (2019)
  • [5] Ahmed et al. Physical Review Applied 10, 014018 (2018)

Prof Michael Tobar (University of Western Australia) 2nd August 2022, 3pm, JA3.14

The Quantum Technologies and Dark Matter research laboratory has a rich history of developing precision tools for both fundamental physics and industrial applications. This includes the development and application of novel low-loss and highly sensitive resonant photonic and phononic cavities, such as whispering gallery and re-entrant cavities, as well as photonic band gap and bulk acoustic wave structures. These cavities have been used in a range of applications, including highly stable low noise classical and atomic oscillators, low noise measurement systems, highly sensitivity displacement sensors, high precision electron spin resonance and spin-wave spectroscopy, high precision measurement of material properties and applications of low-loss quantum hybrid systems, which are strongly coupled to form polaritons or quasi-particles. Translational applications of our technology has included the realization of the lowest noise oscillators and systems for advance radar, the enabling of high accuracy atomic clocks and ultra-sensitive transducers for precision gravity measurements.

Meanwhile, there is currently a world-wide renascence to adapt precision and quantum measurement techniques to major unsolved problems in physics. This includes the effort to discover “Beyond Standard Model” physics, including the nature of Dark Matter, Dark Energy and the unification of Quantum Mechanics with General Relativity to discover the unified theory of everything. Thus, the aforementioned technology has been adapted to realize precision measurement tools and techniques to test some of these core aspects of fundamental physics, such as searches for Lorentz invariance violations in the photon, phonon and gravity sectors, possible variations in fundamental constants, searches for wave-like dark matter and test of quantum gravity. This work includes: 1) Our study and application of putative modified physical equations due to beyond standard model physics, to determine possible new experiments: 2) An overview of our current experimental program, including status and future directions. This includes experiments that take advantage of axion-photon coupling and axion spin coupling to search for axion dark matter. High acoustic Q phonon systems to search for Lorentz violations, high frequency gravity waves, scalar dark matter and tests of quantum gravity from the possible modification of the Heisenberg uncertainty principle.

Peter Kirton (University of Strathclyde) 3rd August 2022, 3pm, JA3.14

Developing accurate simulations of quantum mechanical systems unavoidably involves taking into account coupling to the outside world. Understanding and predicting the behaviour of these open quantum systems provides a formidable theoretical challenge. Yet, such modelling is important for a wide range of physical systems, whose quantum properties are now routinely measured in the lab. These include arrays of superconducting qubits, cold atoms in optical cavities and semiconductor heterostructures. They provide us with carefully controlled devices, made to emulate the behaviour of particular quantum mechanical models, giving us an exciting new way to test our best theories. While the effect of dissipation is often detrimental to the production of interesting quantum states there are cases where the competition between coherent and incoherent processes to lead to the stabilisation of new phases.

In this talk I will outline our groups activities in developing techniques for understanding these phenomena. I will present some results which show the connections between (equilibrium) superradiance and (non-equilibrium) lasing in models of cold atoms coupled an optical mode [1,2]. I will also present a novel numerical technique, TEMPO [3], for accurately finding the dynamics of open systems strongly coupled to their environment. This allows us to relax many of the approximations commonly made to find the behaviour of more realistic models.

  • [1] Kirton and Keeling PRL, 118, 123602 (2017) and NJP 20, 015009 (2018)
  • [2] Werren et al. arXiv:2201.13368 (2022)
  • [3] Strathearn et al. Nat. Commun. 9, 3322 (2018)

Masazumi Fujiwara (Okayama University) 7th September 2022, 3pm, JA3.14

Nanodiamond quantum sensors have attracted great interest to realize nanometre-scale magnetometers and thermometers with high sensitivity. The heart of this technology is measuring the electron spin states of nitrogen-vacancy color defect centres in diamond under the optical microscope observation. Exploring practical applications and system engineering of the spin-optical detection for some specific usages is at the forefront of this technology. In this talk, I will talk about our recent activities on this topic, including temperature sensing in biological samples [1,2] and engineering its on-chip devices [3,4].

  • [1] Fujiwara et al., Sci. Adv. 6, eaba9636 (2020).
  • [2] Yukawa et al., Nanoscale Adv. 2, 1859 (2020).
  • [3] Fujiwara et al., Nanotechnology 32, 482002 (2021).
  • [4] Oshimi et al., Lab Chip 22, 2519 (2022).

Dr Kali Wilson (University of Strathclyde), 3PM, JA3.14

In complex, macroscopic systems, unexpected behaviour emerges which depends crucially on the interactions between individual constituent particles. Such collective behaviour is observed in biological systems, e.g., flocks of birds and schools of fish, and also in the formation of quantum materials such as superfluid helium or superconductors. In quantum systems the collective behaviour can result in the emergence of useful bulk properties such as superfluidity and superconductivity. 

Quantum mixtures formed of ultracold atoms provide an extremely clean and well-controlled system for studies of the cooperative behaviour inherent in superfluidity, with exquisite control over interactions, geometry, and rotation (vorticity). In particular, experimental control of interspecies interactions has enabled recent demonstrations of beyond-mean-field phenomena such as quantum droplets and Lee-Huang-Yang gases. Here the net mean-field interactions are significantly reduced such that quantum fluctuations play a dominate role in governing the behaviour of the system. Quantised vortices, topologically-protected defects, are ideal probes of the quantum-many-body state, as their nucleation, internal structure, and dynamics depend directly on the microscopic physics at play. Furthermore, vortices play an integral role in the dissipation of energy in these systems.  

I will discuss how vortices may be used to probe binary superfluids and quantum-fluctuation-enhanced regimes, and how this will be implemented experimentally using the ultracold atom apparatus that I am currently developing here at Strathclyde.

Konstantinos Lagoudakis (University of Strathclyde)  - TBC

More information to follow

 

John Maddocks (Swiss Federal Institute of Technology Lausanne) 9th November 2022, 3PM, JA 3.14

 

Wednesday's at 3.00pm (unless otherwise stated) 

Colloquia will usually be held in JA3.14
John Anderson Building 
107 Rottenrow, Glasgow

Coffee and Tea served at 4.00 pm.

All Welcome

Coordinated with the Colloquia at the Department of Physics and Astronomy of the University of Glasgow. (They may have donuts but we have free chocolate covered biscuits and coffee!)

Colloquia Schedule 2022-2023

  • 22/06/22 - Swapan Chattopadhyay (Visiting Professor, University of Strathclyde) *
  • 20/07/22 - Fabien Massabuau (University of Strathclyde)
  • 27/07/22 - Alessandro Rossi (University of Strathclyde)
  • 02/08/22 - Prof Michael Tobar (University of Western Australia)
  • 03/08/22 - Peter Kirton (University of Strathclyde)
  • TBC - Kali Wilson (University of Strathclyde)
  • TBC - Konstantinos Lagoudakis (University of Strathclyde)
  • 09/11/22 - John Maddocks (Swiss Federal Institute of Technology Lausanne)

* Note: Outside of regular schedule.

Optical Stochastic Cooling of Electrons

Swapan Chattopadhyay (University of Strathclyde) 22nd June 2022, 3pm, JA3.14 

Stochastic phase space cooling using microwave techniques in the GHz frequency range have been employed historically in particle colliders, leading to ground-breaking discoveries. ‘Cooling’ increases the likelihood of observing rare physics events. The first important advance, conceptual and technological, in this area was stochastic cooling of anti-matter (e. g. ‘antiprotons’) invented by Simon van der Meer (Nobel Prize, 1984), which was instrumental in the discovery of the W and Z Bosons at CERN in 1983 and the ‘top’ quark at Fermilab years later. Stochastic Cooling reduces the random motion of the beam particles through granular sampling and correction of the beams phase-space structure, thus resembling a ‘Maxwell's demon’. The extension of Stochastic Cooling from the microwave regime up to optical frequencies and bandwidths, samples and exploits a charged particle’s radiation reaction to affect its own phase space, leading to increases in the achievable cooling rates by three to four orders of magnitude. I will report on the recent first experimental observation of this achievement in the IOTA ring by a Fermilab team.

Corundum Ga2O3 – the up-and-coming wide bandgap semiconductor for future UV sensing

Fabien Massabuau (University of Strathclyde) 20th July 2022, 3pm, JA3.14

By 2070, the world population is predicted to reach 10.5B inhabitants, and manned space missions as well as settlements on Mars may be on Humanity’s agenda. These predictions forecast extreme pressures on water, food and waste resource management. These challenges are already tangible now, recognised by the United Nations’ Sustainable Development Goals and Net Zero targets.

Ultraviolet (UV) technologies can alleviate these pressures on our Society. The UV range of the electromagnetic spectrum is extremely important with applications including water and air purification, intensive agriculture, medical therapies, and electronics fabrication. Implemented in every household, UV light emission and its monitoring can achieve safe water at the tap, sanitise rooms, or extend shelf-life of food in fridges. Deployed for farming, these technologies can boost crop yields, enable underground farming, and allow reforestation of old farmlands to combat climate change. UV technologies have the potential for substantial impact on the United Nations’ Sustainable Development Goals.

With a bandgap of ca. 5 eV, gallium oxide (Ga2O3) is the leading contender wide bandgap semiconductor for future power electronics and UV sensing application. This compound is highly polymorphic, with the corundum α phase variant (α-Ga2O3) displaying several indisputable assets: (i) it exhibits the largest bandgap (5.3 eV) amongst all phases, (ii) is isostructural with several other semiconducting group-III or transition metal sesquioxides (e.g. In2O3, Ti2O3) and (iii) with the cheap and widely available sapphire (α-Al2O3) substrate.

This presentation will give an overview of the group’s activities on α-Ga2O3 growth, characterisation, bandgap engineering and applications for UV sensing.

The race for the quantum hardware: semiconductors alive and kicking

Alessandro Rossi (University of Strathclyde) 27th July 2022, 3pm, JA3.14

Quantum technologies for computing, sensing and communicating are developing at a relentless pace. However, a consensus has not been reached on what hardware platforms are the most promising to bridge the prototype-to-product gap and take these systems to commercial fruition. Several solid-state systems are currently under scrutiny, ranging from superconductors to topological insulators, as well as 2D and magnetic materials. Among these, semiconductors occupy a privileged position because they leverage the industrial infrastructure that has enabled modern mainstream electronics for decades. In particular, the prospect of employing well-established Complementary Metal Oxide Semiconductor (CMOS) manufacturing and design techniques could be key to realize large integrated quantum systems of practical use.

In this talk, I will provide an overview of my team’s research on three established semiconductors, namely silicon, germanium, and silicon carbide, which constitute the cornerstones of today’s digital, radio-frequency (rf) and power electronics, respectively. Our mission is to take these materials into the quantum realm and develop devices for quantum computing and quantum metrology applications by preserving full compatibility with the CMOS industrial protocols. To this end, I will show how a field-effect transistor can be turned into a device with quantum functions, namely a quantum dot (QD) with exquisite control of individual charges and spins.1 I will highlight the versatility of this technology by showing that one can virtually use the same QD as either a spin-based information quantum2 or an accurate source of quantised electric current3 for metrological applications. Furthermore, by virtue of ambipolar technology, one can operate such devices to control either conduction electrons or valence holes, each with their own merits for different target applications. Finally, I will argue that, in order to scale up QD-based systems, the interfacing of classical control electronics to the underlying quantum hardware will be one of the crucial challenges. I will discuss these challenges, and possible solutions accessible with the aid of existing CMOS architectures, such as Random Access Memory (RAM) integrated circuitry4 in tandem with rf dispersive readout techniques.2,5

References:

  • [1] Yang et al. Nature Communications 4, 2069 (2013)
  • [2] West et al. Nature Nanotechnology 4, 2069 (2019)
  • [3] Rossi et al. Nano Letters 14, 3405 (2014)
  • [4] Schaal et al. Nature Electronics 2, 236 (2019)
  • [5] Ahmed et al. Physical Review Applied 10, 014018 (2018)

Precision Metrology with Photons, Phonons and Spins: Answering Major Unsolved Problems in Physics and Advancing Translational Science

Prof Michael Tobar (University of Western Australia) 2nd August 2022, 3pm, JA3.14

The Quantum Technologies and Dark Matter research laboratory has a rich history of developing precision tools for both fundamental physics and industrial applications. This includes the development and application of novel low-loss and highly sensitive resonant photonic and phononic cavities, such as whispering gallery and re-entrant cavities, as well as photonic band gap and bulk acoustic wave structures. These cavities have been used in a range of applications, including highly stable low noise classical and atomic oscillators, low noise measurement systems, highly sensitivity displacement sensors, high precision electron spin resonance and spin-wave spectroscopy, high precision measurement of material properties and applications of low-loss quantum hybrid systems, which are strongly coupled to form polaritons or quasi-particles. Translational applications of our technology has included the realization of the lowest noise oscillators and systems for advance radar, the enabling of high accuracy atomic clocks and ultra-sensitive transducers for precision gravity measurements.

Meanwhile, there is currently a world-wide renascence to adapt precision and quantum measurement techniques to major unsolved problems in physics. This includes the effort to discover “Beyond Standard Model” physics, including the nature of Dark Matter, Dark Energy and the unification of Quantum Mechanics with General Relativity to discover the unified theory of everything. Thus, the aforementioned technology has been adapted to realize precision measurement tools and techniques to test some of these core aspects of fundamental physics, such as searches for Lorentz invariance violations in the photon, phonon and gravity sectors, possible variations in fundamental constants, searches for wave-like dark matter and test of quantum gravity. This work includes: 1) Our study and application of putative modified physical equations due to beyond standard model physics, to determine possible new experiments: 2) An overview of our current experimental program, including status and future directions. This includes experiments that take advantage of axion-photon coupling and axion spin coupling to search for axion dark matter. High acoustic Q phonon systems to search for Lorentz violations, high frequency gravity waves, scalar dark matter and tests of quantum gravity from the possible modification of the Heisenberg uncertainty principle.

Phase Transitions in Open Quantum Systems

Peter Kirton (University of Strathclyde) 3rd August 2022, 3pm, JA3.14

Developing accurate simulations of quantum mechanical systems unavoidably involves taking into account coupling to the outside world. Understanding and predicting the behaviour of these open quantum systems provides a formidable theoretical challenge. Yet, such modelling is important for a wide range of physical systems, whose quantum properties are now routinely measured in the lab. These include arrays of superconducting qubits, cold atoms in optical cavities and semiconductor heterostructures. They provide us with carefully controlled devices, made to emulate the behaviour of particular quantum mechanical models, giving us an exciting new way to test our best theories. While the effect of dissipation is often detrimental to the production of interesting quantum states there are cases where the competition between coherent and incoherent processes to lead to the stabilisation of new phases.

In this talk I will outline our groups activities in developing techniques for understanding these phenomena. I will present some results which show the connections between (equilibrium) superradiance and (non-equilibrium) lasing in models of cold atoms coupled an optical mode [1,2]. I will also present a novel numerical technique, TEMPO [3], for accurately finding the dynamics of open systems strongly coupled to their environment. This allows us to relax many of the approximations commonly made to find the behaviour of more realistic models.

  • [1] Kirton and Keeling PRL, 118, 123602 (2017) and NJP 20, 015009 (2018)
  • [2] Werren et al. arXiv:2201.13368 (2022)
  • [3] Strathearn et al. Nat. Commun. 9, 3322 (2018)

Vortex Dynamics in Ultracold Quantum Mixtures: Probing Cooperative Behaviour in Superfluid Systems

Dr Kali Wilson (University of Strathclyde) 31st August 2022, 3PM, JA3.14

In complex, macroscopic systems, unexpected behaviour emerges which depends crucially on the interactions between individual constituent particles. Such collective behaviour is observed in biological systems, e.g., flocks of birds and schools of fish, and also in the formation of quantum materials such as superfluid helium or superconductors. In quantum systems the collective behaviour can result in the emergence of useful bulk properties such as superfluidity and superconductivity. 

Quantum mixtures formed of ultracold atoms provide an extremely clean and well-controlled system for studies of the cooperative behaviour inherent in superfluidity, with exquisite control over interactions, geometry, and rotation (vorticity). In particular, experimental control of interspecies interactions has enabled recent demonstrations of beyond-mean-field phenomena such as quantum droplets and Lee-Huang-Yang gases. Here the net mean-field interactions are significantly reduced such that quantum fluctuations play a dominate role in governing the behaviour of the system. Quantised vortices, topologically-protected defects, are ideal probes of the quantum-many-body state, as their nucleation, internal structure, and dynamics depend directly on the microscopic physics at play. Furthermore, vortices play an integral role in the dissipation of energy in these systems.  

I will discuss how vortices may be used to probe binary superfluids and quantum-fluctuation-enhanced regimes, and how this will be implemented experimentally using the ultracold atom apparatus that I am currently developing here at Strathclyde.