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Latest News

Natasha Tomm receives the Prix Schläfli 2022 and the Faculty Prize of the University of Basel!

Natasha Tomm has received two awards for her PhD thesis “A quantum dot in a microcavity as a bright source of coherent single photons” this year!

The first prize was the Prix Schläfli in Physics 2022, awarded by the Swiss Academy of Sciences (SCNAT). The Prix Schläfli is one of the oldest prizes in Switzerland and awards every year the best dissertations in natural sciences. Read more here.

The second one was given by the Philosophisch-Naturwissenschaftliche Fakultät of the University of Basel. Every year the Faculty awards two outstanding dissertations that have demonstrated great importance and quality of the scientific contributions.

Congratulations!!!

Prix Schläfli 2022: Natasha Tomm

Natasha Tomm receives the Prix Schläfli 2022 and the Faculty Prize of the University of Basel!

Quantum interference of identical photons from remote GaAs quantum dots

Recently published in Nature Nanotechnology, we demonstrate quantum interference between single photons from separate quantum dots. Such a demonstration has been attempted multiple times in the past decade and appeared challenging. The problem is the noise: the noise affects the photon creation process of different quantum dots in different ways. Thus, single photons created by separate quantum dots are sometimes distinguishable. Low-noise GaAs quantum dots are employed for our work, each operated in an independent cryostat. Single photons are created from two distant quantum dots and simultaneously sent to two inputs of a beamsplitter. Despite their (different) origins, the photons exhibit bunching in the beamsplitter output with 93% visibility: they are almost identical. Using an optical CNOT operation, we achieve high-fidelity entanglement between photons from two quantum dots. Our results establish low-noise GaAs quantum dots as interconnectable sources of identical photons.

Quantum interference of identical photons from remote GaAs quantum dots

A diamond-confined open microcavity featuring a high quality-factor and a small mode-volume

In out recent publication in Journal of Applied Physics, we report on an open microcavity containing a diamond micromembrane. Despite operation in the so-called diamond confined regime, where the electric field profile inside the cavity is maximized across the diamond-air interface, we demonstrate quality factors exceeding 120 000. We next develop a qualitative model describing the losses in our cavity and determine that the dominant source of losses to be surface waviness – surface textures with dimensions comparable to the cavity beam waist. The large quality factor combined with a small mode volume of 3.9λ03, yield a predicted Purcell factor of 170, a significant improvement over the state-of-the-art.

A diamond-confined open microcavity featuring a high quality-factor and a small mode-volume

A chiral one-dimensional atom using a quantum dot in an open microcavity

In our recent publication in npj Quantum Information we have demonstrated a chiral one-dimensional atom using a single semiconductor quantum dot in a tunable microcavity. In a chiral atom, photons propagating in one direction interact with the atom, while photons propagating in the other direction do not. Here, we achieve strong non-reciprocal absorption of single-photons, a single-photon diode. Proof that chirality arises from a single emitter is found in the nonlinear behaviour at low powers – light propagating in the backward direction of the diode is highly bunched.

A chiral one-dimensional atom using a quantum dot in an open microcavity

A hole spin qubit in a fin field-effect transistor above 4 kelvin

One of the greatest challenges in quantum computing is scalability. Classical computing overcome this problem by integrating bilions of nm-scale fin field-effect transistors (FinFETs) on a silicon chip. Here, we operate a silicon FinFET as a hole spin qubit above 4 K. At this elevated temperature cooling power increases by order of magnitudes compared to typical qubit operation temperatures, such that on-chip integration with control electronics becomes feasible. We achieve fast electrical 3-axis control with speeds up to 150 MHz, single-qubit fidelities at the fault-tolerance threshold, and a Rabi quality factor greater than 87. The devices feature both industry compatibility and quality, yet are fabricated in a flexible and agile way accelerating future development. The work was published in Nature Electronics.

A hole spin qubit in a fin field-effect transistor above 4 kelvin

Richard receives the Nevill Mott Medal and Prize from IOP!

Prof. Richard Warburton received the prestigious Nevill Mott Medal and Prize from the Institute of Physics (UK)! The prize was awarded in recognition of his outstanding research in solid-state physics and quantum optics, especially the invention and application of Coulomb blockade devices to create coherent spin-photon interfaces and quantum light sources. Congratulations!

Read more here: https://www.iop.org/about/awards/2021-nevill-mott-medal-and-prize

Richard receives the Nevill Mott Medal and Prize from IOP!

Optically driving the radiative Auger transition

Radiative Auger is a process that leads to red-shifted satellite peaks in the emission of atoms and solid-state quantum emitters. It is caused by Coulomb interactions between charged carriers. In our recent paper in Nature Communications, we show for the first time that it is possible to turn the whole process around by optical driving of the radiative Auger transition. Possible applications could be fast optical switching or THz spectroscopy.

Optically driving the radiative Auger transition
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